地质专业英语-讲稿08

2024-02-07 来源：客趣旅游网

《地质专业英语1》讲稿

64学时

地质工程03、04级用

余继峰 2005.2

Lesson One The Earth

（4学时）

From classical ([‘] 古典的)times it has been known that the earth is roughly ([

] 概略地)spherical ([] 球形的)in shape. Actually the planet ([] 行星) is shaped more like a slightly flattened (扁平的，压扁的)ball whose polar ([] 两极的) radius ([] 半径)is about 21km shorter than its equatorial

([] 赤道的) radius. The average radius is 6371km. The earth’s specific gravity ([] 地心引力，重力) is 5.5. It is 5.5 times as heavy as an equal volume of water. The specific gravity is greater than that of any other planet in the solar ([] 太阳的，日光的)system, but not appreciably (略微，有一点) different from that of Mercury ([] 水星), Venus ([] 金星) and Mars ([] 火星).

Because the average specific gravity of surface rocks is only about 2.7. The material existing deep within the earth must have a specific gravity well in excess of (超过)the 5.5 average. Very likely (可能), the material at the earth’s center has a specific gravity as high as about 15.

The splendid photographs of the earth taken from space by Apollo ([] 阿波罗) astronauts ([] 宇航员) remind us that our planet is more than a rocky globe orbiting the sun. Whispy patterns of white clouds above the azure ([] 蔚蓝的)blue color tell us of the presence of an atmosphere ([] 大气)and hydrosphere

([] 水圈). Here and there one can even discern ([] 区分，辨别)patches of tan (棕褐色)that indicates the existence of continents. Greenish ([] 呈绿色的)hues ([] 色调)provide evidence of the planet’s most remarkable feature: there is life on earth. THE ATMOSPHERE

We live beneath ([] 在...之下)a thin but vital envelope of gases (气体包层)called atmosphere. We refer to these gases as air. “Pure air”is composed mainly of nitrogen([] 氮气)(78.03%) and oxygen ([] 氧气)(20.99%). The ramianing 0.98% of air is made of argon ([] 氩气), carbon dioxide and minute quantities of other gases. One of these “other”components ([]) found mostly in the upper atmosphere is a form of oxygen called ozone ([] 臭氧). Ozone absorbs much of the sun’s lethal ([] 致命的)ultraviolet ([] 紫外线的) radiation ([] 辐射), and is thus of critical importance organisms ([] 有机体，生物体)on the surface of the earth. Air also contains from 0.1 percent to 5.0 percent of water vapor ([] 水汽，水蒸汽). However, because this moisture ([]潮湿, 湿气) content (水分含量，含水量) is so variable ([] 可变的，变化的), it is not usually included in lists of atmospheric ([] 大气的)components.

Every day, the atmosphere receives radiation from the sun. This solar radiation (太阳辐射) provides the energy that heats the atmosphere and drives the winds.

Distribution ([] 分布) of solar radiation is one of the most important factors in determining the various kinds of climate we experience on the earth. THE HYDROSPHERE

The discontinuous ([] 不连续的，中断的，间断的)envelope of water that covers 71 percent of earth’s surface is called hydrosphere. It includes the ocean as well

as water vapor. The water contained in streams and lakes, water frozen in glaciers ([] 冰川), and water that occurs underground in the pores ([] 孔隙) and cavities ([] 孔穴) of rocks. If surface irregularities ([] 不规则性，无规律性) such as continents and deep oceanic ([] 海洋的) basins (大洋盆地) and trenches ([] 深沟，地沟) were smoothed out (弄平), water would completely cover the earth to a depth of more than two kilometers.

Water is an exceedingly (非常地，极度地) important geologic agent (地质营力). Glacier composed of water in its solid form alter ([] 改变)the shape of the land by scouring (scoure[] 淘刷), transporting and depositing (deposit[] 沉积) rock debris ([] 碎屑). Because water has the property of dissolving many natural compounds(化合物，复合物), it contributes significantly to the decomposition ([] 分解)of rocks and ,therefore, to the development of soils on which we depend for food. Water moving relentlessly ([] 不懈的)down hill as sheetwash (片流), in rills ([] 溪流), and in streams loosens and carries away the particles of rock to lower elevations ([] 海拔，隆起，上升) where they are deposited as layers of sediment ([] 沉积物). Clearly, the process of sculpturing ([] 雕刻)our landscapes (景观) is primarily dependent upon water.

By far the greatest part of the hydrosphere is contained within the ocean basins. These basins are of enormous ([] 巨大的) interest to geologists (地质学家) who have discovered that they are not permanent ([] 持久的，永久的) and immobile as once believed, but rather are dynamic ([] 动态的) and ever changing. There is ample ([] 充足的，丰富的) evidence that the sea floors (海底) move, and that these movements have a direct relation to the formation of mountains, chains (山脉) of volcanoes, deep sea trenches (深海槽) and mid-ocean ridges (洋中脊，ridge[] 山脊). In the ocean are collected the layers of sediment from which geologists decipher ([] 解释)earth history. Here also one finds mineral ([] 矿物，矿石) resources and clues to the location of ore deposits (矿床) elsewhere on the planet. The ocean provides part of our food supply and has a pervasive ([] 普遍的)influence on the climate we experience.

Lesson Two Common Minerals

（5学时）

QUARTZ([] 石英)

The mineral quartz is one of the most familiar and important of all the silicate ([] 硅酸盐) minerals. It is common in many different families of rocks. As mentioned earlier, quartz represents the ultimate ([] 临界的，根本的，最终的) in cross-linkage of silica tetrahedral ([] 四面体的); it therefore will not break along smooth planes. In quartz, the tetrahedral are joined only at the corners and in a relatively open arrangement. It is thus not a dense mineral, but it is quite hard because of the strong bonding in its framework structure (架状结构). When quartz crystals ([] 晶体)are permitted to grow in an open cavity they may develop hexagonal ([] 六边形的)prisms ([] 棱柱)topped by pyramids (棱锥) that are prized by crystal collectors. More frequently, the crystal faces can not be discerned because the orderly addition of atoms had been interrupted by contact with other growing crystals.

Such minerals as chert ([] 燧石,黑硅石), flint ([flint] 燧石), jasper ([] 碧玉)and agate ([] 玛瑙)are varieties of a form of quartz called chalcedony ([] 玉髓). Chalcedony is composed of extremely small fibrous ([] 含纤维的,质状的)crystals of quartz. The crystals are so tiny that their study often requires the use of an electron microscope. Spaces between the crystals are usually occupied by water molecules ([] 分子). Among the varieties of chalcedony, chert is exceptionally abundant in many sedimentary rock units. It is a dense, hard ,usually white mineral or rock. Flint is the popular name for the dark gray or black variety of chalcedony much used by stone-age humans for making tools. Jasper is recognizes by its opaque ([] 不透明的)appearance and red or yellow color derived from ironoxide (氧化铁)impurities (impurity[] 杂质). The term agate is used for chalcedony that exhibits bands (夹层,带)of differing color or texture (质地,纹理). There are many other varieties of quartz minerals than those briefly mentioned here. THE FELDSPARS ([] 长石)

Feldspars are the most abundant constituents of rocks , composing about 60 percent of the total weight of the earth’s crust. There are two major families of feldspars: orthoclase ([] 正长石)or potassium ([] 钾)feldspar group which are the potassium aluminosilicates ([] 铝矽酸盐), and the plagioclase ([] 斜长岩)group, which are the aluminosilicates of sodium ([] 钠)and calcium ([] 钙). Members of the plagioclase group exhibit a wide rang e in composition—from a calcium-rich end member called anorthite ([] 钙长石)(CaAl2Si2O8) to a sodium- rich end member called albite ([] 钠长石) (NaAlSi3O8).Between these two extremes, plagioclase minerals containing both sodium and calcium occur. The substitution of sodium for calcium, however, is not random but rather is governed by the temperature and composition of the parent mineral. Thus, by examining the feldspar content of a once molten ([] 熔铸的)rock it is possible to infer the physical and chemical conditions under which it originated. Feldspars are nearly as hard as quartz and range in color from white or pink to bluish ([] 浅蓝色的)gray. Silica tetrahedra in the feldspars are joined in a strong three-dimensional lattice ([] 格子)that is characterized by planes of weaker bonding in two directions at (or nearly at) right angles

(直角) to each other. Because of this, the feldspars have good cleavage (break along smooth planes) in two directions. The resulting rectangular ([] 矩形的,成直角的) cleavage ([] 解理)surfaces and a hardness of 6 are properties useful in the identification of feldspars.

The plagioclase feldspars provide an example of the manner in which ions can be interchanged in a mineral group. A chemical analysis of specimens ([] 标本,样品)of plagioclase taken from several different rocks would very probably reveal that the proportions of calcium, sodium, aluminum ([] 铝), and silicon (the principal cations ([] 阳离子)in plagioclase) would differ among the specimens. This variability ([] 可变性)occurs because some ions resemble each other in size and electrical properties (电性质) and are thus interchangeable ([] 可互换的)in a given crystal. Calcium and sodium ions are large and nearly identical ([] 同一的) in size. Both aluminum and silicon are small ions and not greatly different in size. Thus, calcium ions might substitute for (代替)sodium ions freely if size alone were the only requirement. However, the electrical neutrality (电中性)of the crystal must also be maintained. The electrical charge (电荷)of the calcium ion is +2, whereas that of the sodium ion is –1. To counteract ([] 中和)the surplus ([] 剩余的)positive charge, an aluminum ion (+3) may substitute for a silicon ion (+1) to maintain electrical neutrality. Thus, Ca2++Al3+ can interchange with Na+ and Si+. This process of interchange ([] 相互交换) is called solid solution (固体溶液).

THE MICA ([] 云母)GROUP

As noted earlier, mica is a silicate mineral having sheet structure (层状结构), and is easily recognized by its perfect and conspicuous ([] 显著的)cleavage in one directional ([] 定向的)plane. The two chief varieties are the colorless or palecolored muscovite ([] 白云母)mica, which is a hydrous ([] 含水的)potassium aluminum silicate (KAl2 (AlSi2O3 (OH)2) and the dark colored biotite ([] 黑云母)mica, which also contains iron and magnesium ([] 镁)(K(Mg, Fe)3AlSi3O2(OH)2). In muscovite mica, two sheets of tetrahedra are strongly held together along their surface inner surfaces by positively charged ions aluminum. These sandwich like paired sheets are in turn weakly joined to others by positively charged ions of potassium. When muscovite is cleaved ([kli:v] 劈开)into paper-thin layers, the separation occurs primarily along the weaker plane where the potassium ions are located. In biotite, magnesium and iron ions hole the inner surfaces of the sheets together, but once again potassium ions serve to weakly join each basic set of paired sheets to its neighbor.

Identification ([] 辨认,鉴定)of large specimens of mica is rarely a problem because of its planar ([] 平坦的)per feet cleavage and the way cleavage flakes ([] 薄片)snap back (迅速跳回)into place when they are bent and suddenly released. The micas are common constituents of igneous ([] 火成的)and metamorphic ([] 变质的)rocks, where they can be recognized by their shiny surfaces and the ease with which they can be plucked loose with a pin or pen knife. Before the manufacture of glass, one of the chief uses of muscovite mica was as window panes ([] 窗格玻璃边,面). This clear mica was quarried (quarry[] 挖出,苦心找出)in Muscovy

([] 俄国)(commonly name for Russia), and thus came to be known as “Muscovy glass” and eventually muscovite. Today, mica is used in the manufacture of electrical insulators ([] 绝缘体)and as a filler (填充物) in plaster ([] 石膏), roofing products and rubber.

HORNBLENDE ([] 角闪石)

Hornblende is a vitreous ([] 玻璃质的)black or very dark green mineral. It is the most common member of a larger family of minerals called amphiboles ([] 闪石), which have generally similar properties. As can be seen from its chemical formula, NaCa2(Mg,Fe,Al)2(Si,Al)2O2(OH), Hornblende contains a relatively large number of elements. Because of the presence of iron and magnesium, hornblende (along with biotite, augite and olivine [] 橄榄石,黄绿) is designated a ferromagnesian ([] 铁镁矿物,含有铁与镁的)mineral. Crystals of hornblende tend to be long and narrow. Two good cleavages are developed parallel to the long axis and intersect ([] 横断,交叉)each other at angles of 56°and 121°. The cleavage is a reflection of the location of planes of weaker bonds that exist between the double-chain units of silica tetrahedral in the atomic ([] 原子的)lattice.

AUGITE ([] 普通辉石)

Just as hornblende is only one member of a family of minerals called amphiboles, augite is an important member of the pyroxene ([] 辉石)family in which many other mineral species ([] 种类)also occur. Its chemical formula Ca(Mg,Fe,Al)(SiAl)2O3 indicates that it too is a ferromagnesian mineral and thus dark colored. An augite crystal is typically rather stumpy ([] 短柱状的)in shape with good cleavages developed along two planed that are nearly at right angles (87°and 93°). Thus, the cross section of a crystal appears nearly square (rather than rhombic ([] 菱形的) as in hornblende). Unlike hornblende which has a double chain silicate structure, augite is constructed of single chains, and this accounts for its having differently shaped cleavage fragments ([] 碎片,片断).

OLIVINE ([] 橄榄石,黄绿)

Olivine, another ferromagnesian ([] 铁镁矿物)mineral, has been mentioned earlier as having isolated silicon-oxygen tetrahedral boned together by iron and /or magnesium ([] 镁)ions. Its formula (Fe,Mg)2SiO4 indicates that it is a solid solution mineral, containing variable proportions of iron an magnesium. The substitution ([] 替代)of these ions for each other is facilitated (facilitate [] 助长,促进)by their having similar ionic radii ([] 半径)and two electrons (电子)in their outer electron shell (电子壳层). The ions in olivine are so strongly held by ionic bonding (结合,粘合)that the mineral has a hardness of 6.5 to Mohs’scale. As you might guess from its name, this glassy-looking mineral often has a green color. Frequently, it occurs as masses of small sugary grains or as tiny vitreous crystals in black lavas ([] 熔岩,火山岩). It is also an important constituent of stony meteorites. If large unblemished crystals of magnesium-rich olivine are found, they may be cut and polished into attractive gemstones ([] 经雕琢的宝石)called peridot ([]

贵橄榄石).

Lesson Three Sedimentary Rocks

（5学时）

Once weathering products (风化产物) have been formed from pre-existing rocks (原岩，先成岩). The next stage in the sequence of events leading to (导致，产生) sedimentary rocks is the removal and transport of those products. Many denudational ([] 剥蚀作用的)agencies (angency[] 媒介), including running water, and moving ice, and wind assist ([] 帮助)in this removal. The wind is an effective agent in picking up and blowing away the smaller and lighter particles. Glacial ([] 冰川的) ice can move very large pieces of rock and carry an immense ([] 巨大的，极大的)load (载重，负荷) of coarse sediment (粗粒沉积物). Streams are also exceptionally ([] 格外地，异常地)effective in carrying not only solid particles of sediment but invisible dissolved salts as well. Ultimately ([] 最后，终于), sediment-laden (携带大量泥沙的，含沙量大的)streams flow into lakes or the sea and their load of sediment is deposited. It may form sandy beaches (沙滩), silty ([] 粉砂质的) flood-plains (泛滥平原，漫滩，洪积平原), and sometimes muddy boggy ([] 沼泽的)areas of estuaries (estuary[] 河口湾)and deltas ([] 三角洲).

The solid particles carried by wind or water will be deposited whenever ([] 无论何时)there is insufficient ([] 不足的) energy to carry them further. For example, if the velocity ([] 速度，速率)of dust-laden wind abates ([] 减少), there will be insufficient energy to carry particles of a given size ,and those particles will be dropped. Similarly ([] 同样地，相似地), if a stream’s velocity is checked (受到阻止，减弱), as when entering a standing (静态的) body of water (水体，储水池), the stream also loses energy and is unable to continue to carry the material formerly carried at the higher velocity.

A reduction in a stream’s velocity does not, of course, affect the dissolved materials as it does suspended ([] 悬挂，悬浮) solid particles. Material carried in solution ([] 溶液)is deposited by a process called precipitation ([] 沉淀作用), in which dissolved material is changed to a solid and separated from the liquid in which it was formerly dissolved. For example, calcium ([] 钙) carbonate ([] 碳酸盐), the principal ([] 主要的) substance in the widespread ([] 分布广泛的，普遍的) sedimentary rock known as limestone ([] 石灰岩), may be precipitated from water that contains calcium in solution as indicated below：

Ca2+ + 2HCO3 CaCO3 + H2O + CO2

(dissolved (dissolved (calcium (water) (carbon

calcium bicarbonate([]) carbonate) dioxide) ions) ions) 碳酸氢盐

The bicarbonate ions that participate in the above reaction can be derived ([] 得到)from the ionization ([] 离子化，电离)of carbonic ([] 碳的，含碳的)acid ([] 酸). As indicated by the arrows, the reaction will proceed toward the right and calcium carbonate will be precipitated. If, however, carbon dioxide is added to sea water, then the amount of carbonic acid in the water would build, and the reaction would proceed to the left. This would result in (导致) a chemical environment not conducive ([] 对...有益的，对...有帮助的) to (有益于) calcium carbonate

precipitation ([] 沉淀(作用)), and one in which existing calcium carbonate might begin to dissolve. As is evident here, the precipitation of calcium carbonate is a complex ([] 复杂的)and delicate ([] 精密的，精细的) process in nature. It is influenced by organisms that utilize or liberate ([] 解放，释放)carbon dioxide, by processes that alter the acidity ([] 酸度) or alkalinity ([] 碱度)of the water, by the presence of organic ([] 有机的) compounds, and by ions of sulfur ([] 硫), phosphorus ([] 磷), and magnesium ([] 镁) which may be present.

Many changes take place in sediment after it has been deposited. Mineral grains (颗粒) may be dissolved away. Some may grow by additions of new mineral matter (矿物质), and the shapes of particles may be distorted ([] 使...变形) by compaction ([] 压实(作用)). The result of some of these changes is to convert ([] 使...转变) sediment into sedimentary rock (沉积岩). The conversion ([] 转变，转换)process is called lithification ([] 岩化). Cementation ([] 胶结(作用)，粘结), compaction and crystallization ([] 结晶(作用)) are the principal means by which unconsolidated ([] 未固结的) sediment is lithified (lithify[] (使)岩化).

Cementation involves the precipitation of minerals in the pore spaces between larger particles of sediment. The precipitated mineral, which most frequently is either calcium carbonate (CaCO3) or silica ([] 二氧化硅) (SiO2), is called the cement ([] 胶结物). Cement is added to a sediment after deposition. It differs from a rock’s matrix ([] 基质) which consists of clastic ([] 碎屑状的) particle (often clay) that are deposited at the same time as the larger grains and help to hold the grains together.

The reduction in pore spaces in a rock as a result of the pressure of overlying (上覆的) rocks or pressures of earth movements is termed compaction. During compaction, individual grains are pressed tightly against one another, causing the expulsion ([] 排出) of water and rearrangement of particles. The result is often the conversion of loose sediment into hard indurated ([] 硬化的)rock. Compaction is greatest and most important as a lithification process in finer-grained sediments like clay and mud.

Lithification by crystallization may begin with an initial ([] 最初的，起始的)chemical precipitate ([] 沉淀物) in which the developing crystals grow together to form a crystalline solid (结晶固体). The process of crystallization, however, may also result in a changing in the form of grains that have already been deposited. For example, quartz may be precipitated onto rounded quartz grains to form a strong interlocking ([] 联锁的，镶嵌的)mosaic ([] 镶嵌) of crystals. Clay may be converted to a matted ([] 缠结的，无光泽的，暗淡的)aggregate ([] 集合体)of tiny mica crystals or calcium carbonate skeletal ([] 骨骼的，骸骨的) debris ([] 岩屑，碎石) may be recognized into hard crystalline calcite ([] 方解石). The migration ([] 迁移，转移)of watery solutions through sediment favors crystallization as does deep burial and consequent ([] 作为结果的，随之发生的) increases in temperature and pressure.

Sedimentary rocks are identified and named according to their composition

([] 组成，成分) and texture ([] 结构). In regard to (关于) composition, the three most abundant mineral components ([]成分) of sedimentary rocks are clay minerals, quartz and calcite. Evaporite ([] 蒸发岩)minerals and dolomite ([] 白云石), although less abundant, nevertheless ([] 然而，不过)form an appreciable ([] 可估计的) portion of many sedimentary sequences. Sedimentary rocks nearly always also contain variable amounts of limonite ([] 褐铁矿) and hematite ([] 赤铁矿). A generalization ([] 概括，广义性) one can make about the mineral composition of sedimentary rocks is that most are mixtures of two or more components in which one mineral may predominate ([] 掌握，控制，支配，统治). Thus, sandstones composed mostly of quartz grains nearly always contain some clay or calcite, and limestones ([] 石灰岩) made mostly of calcite neatly always are contaminated (contaminate[]污染)with clay and quartz grains.

Texture refers to the size and shape of individual mineral grains and to their arrangement in the rock. A rock that has a clastic texture ( from the Greek klastos, broken) is composed of particles of clay, silt ([] 粉砂), sand, and gravel ([] 砂砾，砾石), or fragments of parent rock or fossils ([] 化石) that have been moved individually from their place of origin. In contrast ([] 使与...对照) to (和...形成对比，对照)these clastic rocks, non-clastic rocks form by chemical or biochemical (生物化学的) precipitation within a sedimentary basin. Most non-clastic rocks are crystalline and include certain limestones and evaporates.

Sedimentary rocks made of the remains of plants and animals are categorized as biogenic ([] 源于生物的，生物成因的). Coal, for example, can be considered as sedimentary rock derived from the accumulation ([] 积聚，堆积物)of plant remains. Limestones composed predominantly of the skeletal remains of invertebrate ([] 无脊椎的) animals would also be considered biogenic.

Although it is convenient to separate sedimentary rocks into such discrete ([] 离散的，不连续的)categories as clastic, crystalline and biogenic, it becomes quickly apparent ([] 显然的) to anyone who enjoys collecting rocks that there are many gradational ([] 有等级的)types, and some rocks can be placed in either of two categories with equal validity ([] 有效性，合法性，正确性). For example, many limestones are distinctive ([] 与众不同的，有特色的)crystalline, but a limestone composed of fragments of a pre-existing limestone could be termed as clastic limestone.

Lesson Four Movement and Geological Structures

（8学时）

The eighteenth-and nineteenth-century scientists who laid the foundations of modern geology concluded that most sedimentary rocks were originally deposited as soft horizontal layers at the bottom of the sea and hardened over time. But they were puzzled that many hardened rocks were tilted, bent, or fractured. They wondered, what forces could have deformed these hard rocks in this way? Can we reconstruct the history of the rocks from the patterns of deformation found in the field? The geologists of today would add, how do rocks of all types become deformed, and how does the deformation relate to plate tectonics (Press and Siever, 2001)？These questions are answered in the following.

1 ACTING FORCE AND DEFORMATION OF ROCKS 作用力与岩石变形

All rocks in the crust of the Earth have been deformed, to some extent, by tectonics. We call the forces acting on rocks stresses（应力）.

There are two kinds of acting forces-static forces （静压力） and directed forces （定向压力）. Static forces or confining stresses （围压） make rocks contract their volumes and directed forces or stresses make the rocks change their shapes （Figure 1）.

Directed forces include three types：compression, tension and shear. Compressive forces squeeze the rocks and shorten the rock body; tensional forces stretch a body and tend to pull it apart; and shearing forces push two side of a body in opposite directions （Figure 1）.

Geological structures（地质构造）are the results of rock deformation.

Occurrence（产状） is the orientation of a structural plane or a structural line. It can be described by strike, dip and dip angle.

Strike（走向）is the direction or trend that a structural surface (such as bedding or fault plane) takes as it intersects with a horizontal surface. The direction is expressed with two azimuth values in the opposite directions.

Figure1 Stresses and rock deformation (Adopted from http: //www.earthsci. org)

Dip direction（倾向）is the direction which points to the lower side of a structural plane and is perpendicular to the strike of the surface. The dip is measured at right angles to the strike in a horizontal surface, pointing to the lower side of the inclined plane. If a dip direction is measured, the strike of the surface can be calculated because strike is perpendicular to dip direction. However, if the strike is measured, the dip is still not determined because dip is a radial line.

Dip angle（倾角，dip）is the angle that a structural surface makes with the horizontal ,

measured perpendicular to the strike of the structure ( foreign geologists often use the term dip as dip angle ) . There are true dip and apparent dip, among all the angles the true dip is the largest one (Figure 2, right：δ). Strike, dip direction and dip angle are the three key elements of occurrences (产状三要素) of geological structures.

Figure 2 A sketch diagram showing true dip and apparent tip.

( Left：after Harwoods http：//focweb.bhc.edu/academics/science/harwoodr)

OS-strike; SS’-true dip; δ-true dip angle; ε0-apparent dip angle

2 FOLD AND FRACTURE 褶皱与断裂

There are mainly two kinds of deformation of rocks-fold and fracture, the most common forms of deformation in the sedimentary, that make up Earth’s crust. Folds are the result of plastic deformation, while fractures are the result of brittle deformation. 2.1 Fold 褶皱

Fold (褶皱) is a bent or warped stratum or sequence of strata, which was originally horizontal, or nearly so, and was subsequently deformed. Folds in rocks are like folds in clothing. Just as cloth pushed together from opposite sides bunches up in folds, layers of rock slowly compressed by forces in the crust are pushed into folds. T he geometry of a fold includes core(核) , limb (翼),crest (弧尖) , hinge (枢纽) or fold axis (褶皱轴) , axial plane (轴面) , axial trace (轴迹) ,fold length, width and height etc.(Figure 3)

Figure 3 Geometry of a fold.

( Modified after http：//www. earthsci. org/teacher/basicgeol)

The core is in central part of a fold in which the strata are folded more severely than that of the limbs. The crest is a point in a cross section in which the single stratum of a fold has its largest curvature. All the crests in the same stratum form a hinge or fold axis, and all the hinges of the whole beds in a fold form an axial plane. An axial plane is an imaginary surface that goes through the core of a fold and divides the fold as symmetrically as possible (Figure 3). The axial trace is the intersection line of axial plane with the ground surface.

The basic types of {olds are anticline (背斜) and syncline (向斜). Folds which have both limbs dipping away from the fold axis are called anticlines ( Figure 4, left) ; folds which have both limbs dipping towards the fold axis are called synclines (Figure 4, right). When an anticline is uplifted and eroded, older rocks are exposed near the fold axis and younger rocks are exposed away from the axis. When a syncline is uplifted and eroded, younger rocks are exposed near the fold axis and older rocks are exposed away from the axis.

Figure4 Basic types of folds: anticline (left) and syncline (right). (Adopted from http：//www. earthsci. org/teacher/basicgeol)

Each type of fold can be further classified by the relationship of the axial plane to the limbs. For example, a symmetrical fold (对称褶皱) or vertical fold (直立褶皱) has a vertical axial plane and the two limbs form a mirror image of each other without being overturned in any side(Figure5) Asymmetrical fold (非对称褶皱)or inclined fold (倾斜褶皱) has an inclined axis with both limbs dipping steeper than the other( Figure5) . Overturned fold (倒转褶皱) also has an inclined axis with both limbs dipping to the same direction (i.e. one limb is normal and the other is overturned). A recumbent fold (平卧褶皱) has an almost horizontal axis with both limbs being nearly horizontal too' obviously, in a recumbent fold, one limb is overturned and the other is normal.

Folds can also be classified according to the shapes of folds in cross section, such as fan fold (扇状褶皱，Figure6a) ，box fold (箱状褶皱, Figure6b), chevron fold (尖棱褶皱, Figure6c) and monocline(单斜,Figure 6d) etc.

Folds can also be classified into non-plunging fold and plunging fold according to the orientation of hinges. A fold with horizontal fold axis is called non-plunging （非倾伏褶皱）or upright fold(平轴褶皱), whereas a fold with tilted fold axis is called plunging ford（倾伏褶皱）and its plunge or pitch (倾伏角) is measured as the angle between the fold axis and a horizontal line(Figure 7). Plunging direction (倾伏向) is also important for analyzing the deformation mechanism.

According to their relative length and width, folds can also be classified into linear fold (线状褶皱), in which the ratio of length to width (L/W) is greater than 10, brachy-fold (短轴褶皱),in which the ratio is between 3 and 10, and dome (穹) or basin (盆), in which the ratio is less than 3 ( Figure 8).

Regional fold belts contain large anticlines and synclines, kilometers across, which are marked by the presence of reasonably systematically spaced smaller anticlines and synclines. The flank of an anticlinorium（复背斜）or synclinorium(复向斜) is typically marked by a set of approximately equal-sized second-order anticlines and synclines ( Figure 9, left). These in turn may contain sets of third-order folds, and so it goes. Apart from these very large-scale folds, there are some small-scale folds, centimeters across, often found in strongly deformed metamorphic rocks (Figure l0).The smaller folds are called parasitic folds (寄生褶皱, Figure 9, right).

Figure9 .5 Sketch profiles showing types of folds according

to relationships of fold axis to limbs.

(Modified after http://www.dmtcalaska.org/course-dev/explogeo/classl0/notes10.html)

Figure6 Sketch diagrams showing fan fold, box fold, chevron fold and monocline.

There are still more types of folds according to different criteria. However, the types mentioned above are the most common ones. More and detailed description of fold types can be seen in a classic textbook , Structural geology of rocks and, regions ( Davis and Reynolds, 1996).

Figure7 Sketch diagrams showing non-plunging fold (left) and plunging fold (right).

(Adopted from http: //www.earthsci. org)

Figure 8 Sketch diagrams showing structural basin (left) and dome (right).

A-the oldest formation; E-the youngest formation

Figure9 .9 Schematic rendering of an anticlinorium and synclinorium

(Modified after Davis and Reynolds, 1996)

Figure10 A photo showing small scale folds in a Precambrian metamorphic rock,

Yixian County, west of Liaoning Province.

(Photo by Hongbo Lu, 2005)

2.2 The Recognition of Folds in the Field 褶皱的野外识别

Structural controlled landforms. The folds and faults produced by rock deformation often control the development of landforms.

In young mountains, during the early stages of folding and uplifting, the anticlines form ridges and the synclines form valleys (Figure 11, left). However, as tectonic activity moderates and erosion bites deeper into the structures, the anticlines may form valleys and the synclines form ridges or hills. This happens where the rocks (typically sedimentary rocks such as limestones, sandstone, and shales) exert strong control on topography by their variable resistance to erosion. If the rocks beneath an anticline are mechanically weak, as shales are, the core of the anticline may be eroded into anticlinal valleys, the syncline between the two anticlines would be a synclinal ridge or synclinal hill(Figure 11, right). This landform, due to the geologic structural control, is called relief inversion(地形倒置，地貌倒置) .

Antictinal valley (背斜谷) is a valley which follows the axis of a breached anticline.

Synclinal hill (向斜山) is a mountain in which the geologic structure is that of a syncline. Cuestas (单面山) are asymmetrical ridges in a tilted and eroded series of beds of alternating weak and strong resistance to erosion. One side of a cuesta has a long, gentle slope determined by the dip of the erosion-resistant bed. The other side is a steep cliff formed at the edge of the resistant bed where it is undercut by erosion of a weaker bed beneath (Figure 12, left). Much more steeply dipping or vertical beds of hard strata erode more slowly to form hogbacks (猪背岭), which are steep, narrow, more or less symmetrical ridges ( Figure l2 , right) .

Figure11 Sketch diagrams showing the formation of synclinal ridge and anticlinal valley. In early stages, ridges are formed by anticlines (left); in later stages, the anticlines may be breached and ridges may be held up by caps of resistant rocks as erosion forms valleys in less resistant rocks( right).

(After Press and Siever, 2001)

Figure12 A sketch showing a cuesta(left) and a photo showing hogbacks( right).

(After Press and Siever, 2001)

Observations in the field seldom provide geologists with complete information. Either bedrock is obscured by overlying soils or erosion has removed much of the evidence of former structures. So geologists search for clues that they can use to work out the relation of one bed to another. For example, in the filed or on a map, an eroded anticline would be recognized by a strip of older rock layers forming a core bordered on both sides by younger rock layers dipping away. An eroded syncline would show as a core of younger rocks bordered on both sides by older rocks dipping toward the core. The followings are two principles used by geologists.

Symmetrically repeated strata(地层的对称重复性). If the core is older than the limbs, the fold is an anticline (Figure 8, right; Figure 13); and if the limbs are older than the core, the fold is a syncline (Figure8, left). In Chinese:内新外老—向斜；内老外新—背斜.

Figure13 A sketch diagram showing a plunging anticline.

For a plunging fold, the hinge is always plunging to the younger end of the fold. If the fold is a syncline, the hinge plunges to the open side (younger side); and if the fold is a anticline, the hinge plunges to the close end (still younger end, Figure 13). (倾伏褶皱的枢纽总是向相对新的地层一端倾伏)

Using the principle provided above, geologists typically work from available surface outcrops of rock formation to reconstruct subsurface structures. In fact, folds are typically found in elongated groups. A strip of country in which the rock layers are folded-that is, a fold belt (褶皱带)-suggests that the region was compressed at one time by horizontal tectonic forces. 2.3 Fracture 断裂

We have seen that the way in which rocks deform depends on the kinds of forces to which they are subjected and the conditions that prevail. Some layers crumple into folds, and some fracture. Fractures include faults ( 断层) and joints (节理) . A joint is a crack along which there has been no appreciable movement. A fault is a fracture with relative movement of the rocks on both sides of it, parallel to the fracture. Just like folds, joints and faults tell us something about the forces that a region has experienced in the past. 2.3.1 Faults 断层

Folds usually signify that compressive forces were at work, whereas faults can be caused by all three types of forces: compressive, tensional and shearing. These forces are particularly intense near plate boundaries. Faults are common features of mountain belts, which are associated with plate collisions, and of rift valley, where plates are being pulled apart. Crustal forces also can be strong within plates and cause faulting in rocks far from plate boundaries.

Geologists define faults by the direction of relative movement, or slip, at the fracture. The surface along which the formation fractures and slips is the fault plane or fault surface (断层面).

The two sides separated by the fault plane are called, respectively, hanging wall (above the fault plane, 上盘) and footwall (below the fault plane, 下盘, Figure 14).

Figure 14 A diagram showing the basic geometry of a fault.

The faults can be classified into three basic types：normal faults (正断层), reverse faults(逆断层) and strike-slip faults (走滑断层,平移断层). strike-slip faults and reverse faults are also called dip-slip faults (倾滑断层). A movement along the strike and simultaneously up or down the dip is described as a oblique-slip fault. In fact, there are a lot of oblique-slip faults (斜滑断层), suggesting the combinations of strike-slip and dip-slip movements.

In a normal fault, the hanging wall moved downward and the footwall moved upward along the fault plane. A normal fault is generally induced by horizontal extension in the crust (Figure15, left). The fault plane on a normal fault is generally very steep(>30°, most of them>60°). However, a fault plane with a very low angle(<30°, some geologists prefer <15°) on a normal fault may be present, and in this case the fault is called detachment fault (拆离断层,Figure 16).

Figure9 .15 Block diagrams showing normal fault (left) and reverse fault (right).

(Adopted from http：//www. earthsci. org)

A reverse fault is one in which the rocks above the fault plane move upward in relation to the rock below, causing a shortening of the section (Figure 15, right). That is to say, reverse faulting results from compression.

Figure 16 Block diagram showing a detachment fault.

(After Harwoods, 2005)

A reverse fault at which the dip of the fault plane is small (usually <30°, but some geologists prefer <15°), so that the hanging wall is pushed mainly horizontally, is called a thrust

fault (逆冲断层, Figure 17, left). Furthermore, a large-scale thrust fault, in which the thrust sheet(hanging wall) has been moved a great distance horizontally, is called overthrust fault (逆掩断层). In this case, the large thrust sheet (逆冲片) having moved a long distance and resting on the autochthonous basement (本地基底,footwall) is called a nappe (推覆体). When the nappe (thrust sheet) has been eroded in some place and thus the basement has been exposed (in a small area relative to the nappe), the exposed area is called a structural window (构造窗). If most part of the nappe has been eroded and the basement around the nappe has been exposed, the residual nappe is called a klippe (飞来峰). In its restrict definition, a klippe is a large body or sheet of rock that has been moved a distance of about 2 km or more from its original position by faulting. A nappe , in other words , is an isolated residual part of the hanging wall of an overthrust fault, or even a part of a recumbent fold (www. britannica. com). The hanging wall above the fault surface is called allochthonous rocks (外来岩块), and the rocks below the fault surface are called autochthonous rocks (本地岩块,Figure 17, right).

Figure17 A block diagram showing a thrust fault (left), and a cross-sectional sketch showing

nappe, klippe and window. (After Harwoods, 2005)

Large overthrust faults occur in areas that have undergone great compressional forces. These conditions exist in the orogenic belts that result when two bontinental plates collide. The resultant compressional forces produce mountain ranges. The Himalayas, the Alps and the Appalachians are prominent examples of compressional orogenies with numerous overthrust faults.

A strike-slip fault (走滑断层) is one in which the movement is horizontal, parallel to the strike of the fault plane. When we face a strike-slip fault (i.e. we stand on one side of fault), we can find its movement direction relative to each side of the fault. If the block on the other side is displaced to the right, the fault is a right-lateral fault or dextral fault (右旋断层,Figure 18,right) ; if the block on the other side of the fault is displaced to the left, it is a left-lateral fault or sinistral fault (左旋断层,Figure 18, left). These movements result from shearing forces.

Figure18 Block diagrams showing sinistral(left) and

dextral(right) strike-slip faults. (After Harwoods, 2005)

Cross sections of regions of normal faulting generally emphasized the presence of \"horsts\" and \"graben\". Horsts (地垒) are relatively uplifted, generally unrotated blocks bounded on either side by outward-dipping normal faults. Grabens (地堑), on the other hand, are relatively downdropped, relatively unrotated blocks bounded on either side by inward-dipping normal faults (Figure 19). Horsts and grabens are classical terms describing fault-bounded uplifted and

down-dropped blocks, respectively, in extended regions.

Figure19 A block diagram showing graben and horst

(Modified after Harwoods，2005)

Half-graben (半地堑) is a normal fault that has a curved fault plane with the dip decreasing with depth can cause the down-dropped block to rotate. In such a case a half-graben is produced ( Figure 20) . It is called such because it is bounded by only one fault instead of the two that form a normal graben. It is also called a listric normal fault (犁式正断层) because the fault plane is curved or \"spoon-shaped\".

The evidences of faults (断层的证据). Direct evidences of faulting can often be difficult to locate due to the effects of weathering at the surface which tends to obscure the related features. Even though, geologists have found several types of features that provide direct evidence of faulting.

Figure20 A block diagram showing half-graben generated by horizontal tensile stress.

(Adopted from http: //www. earthsci.org/ teacher/ basicgeol)

Slickensides (擦痕，摩擦镜面) are scratch marks that are left on the fault plane as one fault block moves relative to the other. A slickenside is a smooth, striated, polished surface. Slickensides can be used to determine the direction and sense of motion on a fault (Figure 21). Orientation of the scratching indicates the direction of the most recent movement of the fault, and so it does not tell the whole history of the fault movement. Thus, we should use this indicator with caution.

Figure21 A sketch diagram showing slickenside on a fault plane (left), and a photo showing slickenside on a fault plane, Shandong Province, China

(Adopted from http：//homepage. usask. ca/~mjr347/prog/geoe118/geoe118.05.html;

photo by Hongbo Lu, 2005)

Faults are shear planes and commonly contain the debris from the frictional contact of the two surfaces. In strong rocks, material is fragmented to create a zone of crushed rock or fault breccia. In weaker rocks, the material in the fault plane can be reduced to a very fine clay-size infill known as fault gouge.

Fault breccia (断层角砾岩) are the rocks or unconsolidated materials consisting of rock fragments (Figure 22,left; Figure 23, left). Occurs on either or both sides of the fault plane, breccia may form a zone which obscures the fault plane entirely.

Fault gouge (断层泥) is very fine-grained, unconsolidated material consisting of pulverized rock fragments (Figure 22, right; Figure 23, right). It is produced when fault blocks were passing each other. Thus, fault gouge looks like clays (in white, red, brown or gray and sometimes even black color) distributed along the fault belt.

Figure22 sketches showing fault breccia (left) and gouge (right).

(Modified from http://homepage. usask.ca/~mjr347/prog/geoe118/geoe118.052. html)

Figure23 Fault breccia (left) and gouge (right) in Aerjin Fault belt,

northwest of China. (Photo by Hongbo Lu, 1996)

Apart from fault breccia and gouge that can be found on the fault plane, other marks on the sides of faults can also be used as some fault indicators, such as drag folds or joints. A drag fold (拖曳褶皱) is a fold induced by fault block movement , the crest of the fold points to the movement of the same wall (block) beside the fault plane (Figure 24).

Indirect evidence of faulting can also be present. This type of evidence may include the juxta-position (重叠，并置) of two map units which are usually not contiguous (相邻的), such as two sedimentary rock formations of different ages, or an intrusive in sharp contact with a country rock instead of containing a hornfels(角页岩) or skarn(矽卡岩) zone in between. Geologists also examine topographic maps and aerial photographs for linear features on the surface' Lastly' aeromagnetic anomalies (航磁异常) or other linear aeromagnetic features can be indicatives of large scale fault structures.

Apart from the evidences mentioned above, there are some marks in relief for identifying

faults，such as fault scarp, valleys, rivers (Figure 25) and springs etc. All these are the relics or marks of faults exposed on the ground.

The dotted line is the fault trace and the lined areas are the fault scarps Figure25 Fault scarps along Xilamulun River, north of Chifeng, China.

(Photo by Hongbo Lu, 2004)

In a geological map or a cross section, asymmetrically repeated identical strata or lack of some identical strata may be good clues for identifying a fault and its displacement' There are six different combinations as listed in the Table 1. A geologist can easily reconstruct the repeated or missing portions of the structure and the relative motion directions of the fault blocks.

In fact, faults (including jointing) and folds are often related, so there are fault-related folds (断层相关褶皱) such as fault propagation fold (断层传播褶皱) and fault bend fold (断层转折褶皱), etc.

Table 1 Relationship between the orientation and the fault results

2.3.2 Joints 节理

Joints, which can be caused by tectonic forces, are found in almost every outcrop. Like any other brittle material, brittle rocks break more easily at flaws or weak spots when they are subjected to pressure' These flaws can be tiny cracks, fragments of other materials, or even fossils. Regional forces (compressive, tensional or shearing) that have long since vanished may leave their

imprint in the form of a set of joints (Press and Siever, 2001; Figure 26, upper left). Joints can also be caused by non-tectonic reasons, such as expansion and contraction of rocks or even contraction of loess (Figure 26, upper right). Joints, in fact, can be treated as sets of faults with very small displacements. Joints can range in size from microscopic to kilometers in length. Joints have a major influence on landform development, because erosion is able to occur at a faster rate along joints. Joint spacing is often rather consistent within a specific rock type in a specific environment. For example, fine-grained rocks tend to have close-spaced joints, while coarse-grained rocks tend to have wide-spaced joints. The jointing pattern within a specific rock type is sometimes so consistent that it can often be a useful aid for geologic mapping.

Figure26 Shear joints in the Mesozoic sandstones, west of Liaoning Province (upper left); contraction joints in loess in the north of Chifeng, Inner Mongolia (upper right); vertical shear joints in the granite in Dazhushan, Qingdao, China( lower).

(Photos by Hongbo Lu)

3 CONTACT RELATIONS 接触关系

There are many kinds of contact relations between rock units or strata, and different relations have different geological meanings (Figure 27).

a. Conformity (整合). True stratigraphic continuity in the sequence of beds without evidence that the lower beds were folded, tilted, or eroded before the higher beds were deposited.

Figure27 Sketch diagrams showing different contact relations

Left: A-Cambrian strata; B-Early Paleozoic intrusive granite; C-Late paleozoic strata; D-Late Paleozoic strata; E-Mesozoic strata; F-Mesozoic strata. Then, the relations between A and B-intrusive contact; C and A-angular unconformity; C and B-sedimentary contact. C and D-conformity; D and E are in disconformity or parallel unconformity; E and F are in conformity. Right: fault contact (a vertical fault separates the strata and the rock units of the two blocks)

b. Unconformity (不整合) indicates a substantial break or gap in the geologic record where a rock unit is overlain by another that is not next in stratigraphic succession, such as an interruption in the continuity of a depositional sequence of sedimentary rocks or a break between eroded igneous rocks and younger sedimentary strata. There are three different kinds of unconformities.

Angular unconformity (不整合或角度不整合) is an unconformity in which the younger overlying sediments rest upon the eroded surface of tilted or folded older rocks.

Disconformity (非整合) is an unconformity in which the bedding planes above and below the break are essentially parallel, indicating that the older rocks remained essentially horizontal during erosion or during simple vertical rising and sinking of the crust. It is also called parallel unconformity(平行不整合).

Nonconformity (非整合) is an unconformity developed between sedimentary rocks and older rocks( mainly plutonic igneous) that had been exposed to erosion before the overlying sediments covered them. It is also called sedimentary contact (沉积接触).

c. Intrusive contact (侵入接触) is the contact of intrusive body with the sedimentary country rocks.

d. Faulting contact (断层接触) means that different geological bodies contact with each other with fault.

All mentioned above in this chapter belong to the study of structural geology (构造地质学) . Geological structures are very important for geologists to explore all kinds of ore deposits, including oil and gas. Fractures and fault zones provide excellent pathways for hydrothermal fluids to circulate through. Open-space filling has long been recognized as the primary method of vein formation. The formation of breccia and gouge due to the grinding action of the rocks adjacent to the fault plane increases the “structural porosity”, which in turn increases the permeability. Under certain conditions, breccia or gouge may itself provide the host for mineralization. Intersections of structural features often are better locations to prospect for mineralization, especially where the structures are high angle. It is thought that the intersection of high angle structures provides pathways for fluids from deep sources to move closer to the surface.

4 TECTONICS (GEOTECTONICS) AND SOMETHING IN THE HISTORY OF GEOLOGY 大地构造学及地质学中某些史事

Tectonics (大地构造学) is a branch of geology dealing with the broad architecture of the upper part of the Earth' s crust, that is, the regional assembling of structural or deformational features，a study of their mutual relations, origin, and their historical evolution.

It is closely related to structural geology, but it generally deals with the larger features (such as orogenic belt, sedimentary basin) and structural geology deals with the smaller features (such as folds and faults).

To talk about geotectonics, we had better review some great events in the history of geology. Among the events, three great controversies in the history of geology should be mentioned. They

are Neptunism versus Plutonism(水成论与火成论) , Catastrophism vs. Uniformitarianism(灾变论与均变论), and Fixism vs. Mobilism (固定论与活动论). These great controversies resulted in great revolution and advancement in the geological theories. 4.1 Neptunism and Plutonism 水成论与火成论

This is a debate concerning the origin of rocks.

The representative of Neptunism was a German geologist, Abraham Gottlob werner (魏格纳) . He was born on September 25,1750, in Wehrau,Saxony, and died on June 30,1817. Werner founded the Neptunist school, which proclaimed the aqueous (水成论) origin of all rocks, in opposition to the Plutonists, or Vulcanists, who argued that granite and many other rocks were of igneous origin.

Werner's father was a supervisor in a steel-casting company. From young Werner was educated by his father, and so he was interested in mining. He graduated from Freiberg Mining Academy first, and then was enrolled in the University of Leipzig (莱比锡大学) . He liked traveling，and so he collected a lot of mineral samples and reviewed a great deal of geological research papers. He published his first academic paper on mineral classification while he was still a student at the University of Leipzig in 1774. From 1775 he started working at Freiberg Mining Academy as a professor until he died in 1817. He was single all his life.

Because Werner was good at expressing his idea and giving lectures to students, a lot of students from around the world came to Germany to follow him. Apart from his popularity, his driving force was primeval sea (原始海, Diluvialism 大洪水-Biblical flood of Noah) and thus he got support from religion. He tried to explain everything with the primeval sea. For example, he thought that basalt was igneous rock but it was formed by the heating of coal underground. After Werner's death, the supporters of Plutonism showed the followers of Neptunism the phenomena in which granite intruded sedimentary beds. Gradually, researchers started believing that Plutonism was right. Although he was wrong about the formation of rocks, Werner was still a great geologist on mineralogy, petrology, ore deposits and stratigraphy.

The scientist who most personified the opposition to Werner’s ideas was James Hutton (1726-1797), a Scotsman who was both a Plutonist and a Uuniformitarian.

James Hutton (郝屯，哈屯，郝顿) of Edinburgh, was interested in chemistry as a youth, did medicine at the Sorbonne (巴黎大学前身的索邦神学院) in Paris, and Leiden University(莱顿大学) in Holland, getting a doctorate for a thesis on blood circulation. On his return to England, however ' he became a farmer. His long-standing interest in chemistry led to a successful partnership in a small industrial concern (公司) making sal ammoniac (氯化氨). This afforded him the financial independence to quit farming, and rectum to Edinburgh to pursue scientific enquiries, a very specific example of how pure research needs surplus wealth in order to thrive.

Although Hutton had learned chemistry, pharmacy, medicine and law, his interest was geology. When he worked as a farmer, Hutton studied mineralogy and geology himself.

Hutton was, like Werner, a lifelong bachelor (单身); his social life revolved around the Oyster (牡蛎) Club (沉默者俱乐部) in Edinburgh. After Paris, Edinburgh was an intellectual center of Europe at the time-the \"Athens of the North (北方的雅典)\". Hutton's friends and contemporaries in this circle include many notables, among them the economist Adam Smith, the philosopher David Hume, Joseph Black, the chemist, and John Playfair, the mathematician.

Black (布莱克,1728-1799)was the strongest scientific influence on Hutton, although they were very different in character. Black feared mistakes, Hutton ignorance (无知); Black was

careful and mindful of popular opinion, Hutton enthusiastically careless. Arguably, he would have made a great teacher, as Werner was, had Hutton been interested in being an academic.

As was not uncommon in those days (Darwin being another example), Hutton took decades to go from the formulation of his ideas to their publication. His important ideas emphasized theoretical concepts; Hutton was not a dedicated field geologist like von Humboldt or von Buch. However, his theories were based on observed facts that granite intruded in sedimentary beds, whether of his own or of others. He submitted his first academic paper about the Earth in 1785 when he was 59 years old. However, he was laughed at by many notable scientists because of that paper. Ten years later, he rewrote his paper and published again. Unfortunately, he was not good at expressing himself, and not got support from religion. His idea was not recognized by academic communities of his time' he was died in (1797).

Who made Hutton's idea a popular theory? His close friend, John Piayfair！The death of his friend, James Hutton, moved Playfair to compose a biographical memoir, which gradually became a reply to the critics of Hutton's theories of geology. This in turn gave rise to Playfair's geological work Illustration of the Huttonian theory of the Earth. Playfair presented Hutton's theories in a different style from Hutton’s original presentation. Hutton had a rather peculiar style of presentation which made his theory less intelligible and, as a result, he had received less acclaim than he deserved. It was a style which led to many erroneous misrepresentations and to attacks from the few who had read it. Playfair's simple and eloquent style consisted of a series of chapters clearly stating the Huttonian theory, giving the facts to support it, and the arguments given against it. The success of Playfair's presentation can be judged by the fame and credit which have since been given to Hutton, who is now regarded as the first great British geologist.

Hutton’s contributions were twofold, and of immense importance： 1) a system of processes which we would regard as an early formulation of the rock cycle, based on Plutonism, and 2) a context(uniformitarianism) in which these took place indefinitely-an Earth of immense age in which these processes had gone on for so long that the evidence of the rocks provided, in Hutton's words, “no vestige of a beginning, no prospect of an end”. In both of these contributions, he collided directly with Wernerian ideas.

4.2 Catastrophism and Uniformitarianism 灾变论与均变论

This was a debate related to the evolution of the Earth and its lives. In fact, it seems that this debate is the continuation of the last debate.

The representative of Catastrophism was French naturalist, zoologist and statesman, Georges Cuvier(居维叶,1767-1832). He established the sciences of comparative anatomy and paleontology.

In 1784-1788 Cuvier attended the academic Caroline (Karlsschule) in Stuttgart, German, where he studied comparative anatomy and learned to dissect. He had an excellent talent on literature, and he was good at getting along people. This made him a scientist and a politician.

He found that different sedimentary beds in Paris basin had different kinds of fossils. Some of the fossils obviously represented the living things not existing on Earth today. This was a great discovery. It means that the Earth is evolving! If he had not been a politician but a pure scientist, he would have been the greatest scientist at his time and Darwin could have been only his follower. Unfortunately, Cuvier wanted to reconcile science with politics or religion. He had to use Biblical creation to explain the extinction and emergence of life on Earth. The only driving force for his dogma was Biblical Diluvialism.

The representative of Uniformitarianism was English geologist Charles Lyell (1197-1875). He was the founder of actualism. He was born in England in 1797 when Hutton died (any relations between them?). Lyell's father was a scientist, having a family library at home and abundant samples of animals and plants. Lyell read a lot of books when he was young. He was clever and keen on learning languages. He started learning English at 8, Latin at 10 and French at 13. He was enrolled in Oxford University at 17, and changed his specialty to law at 19. However, he gave up his career in law but pursued his future in geology. He liked Playfair's work, Illustrations of the Huttonian Theory of the Earth, and conducted a lot of field investigation. He published his book, The Principles of Geology, in 1930. He wrote, \"The present is the key to the past.” The words have been treated as the key concept of actualism.

Although uniformitarianism is the foundation of modem geology, catastrophism still exists today. We have to examine both theories and have our own opinion. 4.3 Fixism and Mobilism 固定论与活动论

This was a debate related to crust movement. The Fixism stresses vertical movement of the crust (to form mountain or ocean basin) while Mobilism stresses lateral movement of the crust as the major reason for oceans and mountain ranges to form.

The representative doctrine of Fixism is the theory of geosyncline and platform founded by American geologist Hall(霍尔,1811-1898) in 1859, and later named by Dana (丹纳,1813-1859). The present geosynclines are oceans, and the present platforms are the continents.

According to this theory, a geosyncline can evolve and, eventually change to a platform, which is a geological cycle. There are a lot of geological cycles in the history of the Earth; and there are different names in different areas or countries although some of the names can be compatible.

The following are some large cycles adopted by geologists in China (Bangdong Xia, 1995). Archaeozoic Megacycle (太古宙巨旋回) ：4,200 to 2,500 Ma (some geologists prefer 3, 800 to 2, 500 Ma, Ar).

Proterozoic Megacycle (元古宙巨旋回) , 2,500 to 2,000 Ma ( Pt1) . Sinian-Caledonian Cycle(震旦-加里东旋回), 2,000t o400Ma( Z-S3). Hercynian Cycle(海西旋回):400 to 250 Ma (D1 –P2). Indochina Cycle (印支旋回)：250 to 200 Ma (T1 – T3). Yanshan Cycle(燕山旋回): 200 to 65 Ma (J1 –K2).

Himalayan Cycle(喜山旋回): 65 Ma to present (E1-Qh).

There are more other geological cycles, and the boundaries separating the cycles are the formation of fold belts or orogenic belts (Bangdong Xia, 1995). All these geologic cycles can be better explained with the theory of plate tectonics (see Chapter 10).

The representative of Mobilism should be Alfred Wegener(1880-1930), who founded the theory of continental drift.

Perhaps Alfred Wegener's greatest contribution to the scientific world was his ability to weave seemingly dissimilar, unrelated facts into a theory, which was remarkably visionary for the time. Wegener was one of the first to realize that an understanding of how the Earth works required input and knowledge from all the Earth sciences.

Wegener's scientific vision sharpened in I9I4 as he was recuperating in a military hospital from an injury suffered as a German soldier during World War I. While bed-ridden, he had ample time to develop an idea that had intrigued him for years. Like others before him, Wegener had

been struck by the remarkable fit of the coastlines of South America and Africa. But, unlike the others, to support his theory Wegener sought out many other lines of geologic and paleontologic evidence that these two continents were once joined. During his long convalescence, Wegener was able to fully develop his ideas into the Theory of Continental Drift, detailed in a book titled The Origin of Continents and Oceans, published in 1915.

Wegener obtained his doctorate in planetary astronomy in 1905 but soon became interested in meteorology; during his lifetime, he participated in several meteorologic expeditions to Greenland. Tenacious by nature, Wegener spent much of his adult life vigorously defending his theory of continental drift, which was severely attacked from the start and never gained acceptance in his lifetime. Despite overwhelming criticism from most leading geologists, who regarded him as a mere meteorologist and outsider meddling in their field, Wegener did not back down but worked even harder to strengthen his theory.

A couple of years before his death, Wegener finally achieved one of his lifetime goals 3 an academic position. After a long but unsuccessful search for a university position in his native Germany, he accepted a professorship at the University of Graz in Austria. Wegener's frustration and long delay in gaining a university post perhaps stemmed from his broad scientific interests. As noted by Johannes Georgi, Wegener's longtime friend and colleague, \"One heard time and again that he had been turned down for a certain chair because he was interested also, and perhaps to a greater degree, in matters that lay outside its terms of reference-as if such a man would not have been worthy of any chair in the wide realm of world science.”

Ironically, shortly after achieving his academic goal, Wegener died on a meteorologic expedition to Greenland. Georgi had asked Wegener to coordinate an expedition to establish a winter weather station to study the jet stream ( storm track) in the upper atmosphere. Wegener reluctantly agreed. After many delays due to severe weather, Wegener and14 others set out for the winter station in September of 1930 with 15 sledges and 4,000 pounds of supplies. The extreme cold turned back all but one of the 13 Greenlanders, but Wegener was determined to push on to the station, where he knew the supplies were desperately needed by Georgi and the other researchers. Travelling under frigid conditions, with temperatures as low as minus 54 T , Wegener reached the station five weeks later. Wanting to return home as soon as possible, he insisted upon starting back to the base camp the very next morning. However, he never made it; his body was found the next summer.

The above material was cited from USGS.

There are other controversies in the history of geology. A very good book, Great Ceological Controversies, covers many of the most important ideas that have emerged since the birth of the science (Hallam, 1990).

KEY POINTS OR QUESTIONS

1. Directed forces and static forces acting on rocks and the rock deformations.

2. Three key elements of occurrences: strike, dip and dip angle, relationship between strike and

dip.

3. Basic fold elements 3 anticline, syncline, core, limbs, crest, hinge, fold axis, axial plane

(surface), axial trace, plunging direction and plunge angle (pitch). 4. Basic fold types：vertical fold, oblique fold overturned fold, recumbent fold, facing-down fold,

fan fold, box fold, monocline, plunging fold, Linear fold, structural basin, dome, anticlinorium, synclinorium, cuesta, hogback, synclinal hill and anticlinal valley etc.

5. Key criterion for recognizing folds on a cross section: symmetrical repeat of strata (syncline;

inner stratum is younger than the outer stratum; anticline3 inner stratum is older than the outer stratum).

6. Basic fault elements; hanging wall, footwall, fault plane or fault surface, displacement etc. 7. Basic types of faults: normal fault, reverse fault, strike-slip fault, trust fault, overthrust, nappe,

klippe, structural window, graben, horst, sinistral and dextral strike-slip faults.

8. The key criterion for recognizing faults; drag fold, fault breccia, striations, slickenside, fault

gouge (fault clay), fault-related joints, fault delta, fault scarp, lack of strata or asymmetrically repeated strata etc.

9. Six contact relations: conformity, unconformity (angular unconformity), disconformity or

parallel unconformity, sedimentary contact, intrusive contact, fault contact. 10. Tectonics and structural geology.

11. Three great controversies in the history of geology and their representatives. REFERENCE

Davis G. H., and Reynolds S. J. Structural geology of rocks and regions (2nd ed.). New York: John Wiley & Sons, Inc., 1996, p.716

HaIIam A. Great geological controversies (2nd ed.). Oxford University Press,1990, p.256

Press F., and Siever R. Understanding Earth (3rd ed.). New York: Freeman and Company, 2001, p.573

Lesson Five Coal-Forming Environments

（4学时）

For a mat of dead vegetation ([] 植被，植物)to be preserved as peat ([] 泥炭) which is ultimately ([] 最后，终于) transformed into coal, the area must be protected from detrital ([] 碎屑的)influx ([] 流入，注入)and the water table (潜水面) must remain at or near the ground surface with no pronounced ([] 明显的)seasonal lowering. Ideally ([] 理论上), the water table should rise slowly and continuously ([] 不断地，连续地) as the area subsides ([] 下沉，下降，沉降) to keep pace with (与...齐步前进) vertical growth of the peat mat. Vegetable matter is rapidly oxidized (oxidize,[] 使氧化)on exposure ([] 暴露) whereas ([] 然而，尽管，但是)prolonged (长期的)submergence ([] 浸没，淹没)terminates (terminate,[] 结束，终止) peat accumulation. A low pH of the peat swamp (泥炭沼泽)waters is critical, total degradation ([] 使降级，退化) results at values higher than 5.0. Even a temporary ([] 暂时的，临时的)decrease in acidity ([] 酸度)may degrade the peat surface to the extent that inorganic ([] 无机的)constituents ([] 要素) of the cellular ([] 蜂窝状的，细胞状的，多孔状的)structure of swamp vegetation are preferentially ([] 优先地) concentrated on the surface, subsequently ([] 后来，随后) to be preserved in coal seams (煤层) as ash bands (夹矸). Similar authigenic ([] 自生的) partings (parting,夹层) in seams may also arise from burnings (燃烧，煅烧)or emergence oxidation ([] 氧化)of the peat surface. Prolonged marine ([] 海洋的，海相的)incursion ([] 侵入作用) (marine incursion 海侵)is another factor that significantly reduces the preservation ([] 保存)potential of a peat.

Conditions favorable([] 有利的) for (favorable for，对...有利)peat accumulation prevail in paralic ([] 近海的)coal-forming environments of humid ([] 潮湿的) coastal plains (滨海平原)as southern New Guinea ([] 几内亚), parts of West Africa and the Gulf and Atlantic ([] 大西洋的) coastal plains of the United States. According to Diessel over 90 percent of all coals formed in a paralic setting. The other broad category of coal-forming environments, limnic ([] 湖泊的，湖沼的), is represented by alluviated ([] 冲积物覆盖的) interior ([] 内部的)basins (alleviated interior basin，冲积内陆盆地) such as the upper Nile and Amazon ([] 亚马逊河), and infilled (充填的)lake systems such as the Okavango of Botswana.

The bulk ([] 大量) of the peat mat tends to be provided by collapse and decay ([] 腐烂)of the plant cover (植被), but this is segmented (segment,[] 分割) in some areas by driftwood (漂木) and floating leaves. Rate of peat accumulation largely depends upon climate, being some four times more rapid in tropical ([] 热带的)forests than in swamps with lower rainfall. Open marshes (草本沼泽) tend to be dominated by reeds and other herbaceous ([] 草本的)plants and accumulate large quantities of fungal ([] 真菌的)spores (spore [] 孢子). Marshes by definition are devoid of (be devoid of 缺少，缺乏)trees, so the resulting peat has no

woody material. Swamps (木本沼泽)contain a variable ([] 可变的，易变的) amount of woody vegetation which increases in proportion ([] 比例)in forest swamps and drier forests with dense stands of large trees. Aquatic ([] 水生的)and semiaquatic ([] 半水生的)plants contribute material to abandoned river channels (废弃的河道), ponds and lake floors (湖底), which commonly also receive transported debris. These lake floor accumulation include the degradation products of pre-existing peat beds (peat bed，泥炭层)to which are added algae ([] 藻类，海藻)and spores.

All of these different plant communities (plant community, 植物群落) give rise to (引起，使发生，导致)distinct maceral ([] 煤显微组分) types in coal. For example, stunted ([] 矮小的)herbaceous plants and grasses produce inertinite([] 惰性组物质)-rich coal, whereas an abundance of large trees gives rise to a high vitrinite (镜质组)content. But maceral content is also influenced by factors of hydrochemistry ([] 水质化学)and level of the water table.

Most vegetated coastal lowlands (低地) show a parallel ([] 平行的)zonation ([] 带状排列，分带性，地带性)of plant communities, reflecting differences in maturity ([] 成熟度), substrate ([] 基质) consistency ([] 一致性), salinity ([ 盐分，盐度), and groundwater (地下水) level. The groundwater level affects not only the living community, but also controls the biochemical environment in which the dead vegetal matter accumulates and is preserved. In modern tropical areas, mangroves (mangrove,[] 红树林) extend to (延伸，延长) the limits of aeration ([] 通风) corresponding approximately ([] 相似地，大约地) to neap high water (小潮高水位). Mangroves commonly show a well-defined zonation depending upon frequency of tidal ([] 潮汐的)inundation ([] 洪水), and merge landward into dense fresh-water swamps; marshes are conspicuously ([] 显著地，超群地) absent. Away from the tropics, mangroves gradually give way to a belt of marsh in the most youthful, seaward portion of prograding lowland: this merges inland into treebearing swamps. Where riverine ([] 河流的)discharge is large and unconfined, fresh-water marsh may extend to the water’s edge. More commonly, however, belt of saline ([] 盐的，含盐的) marsh forms along the zone affected by tidal incursion (海侵作用), and is succeeded ([] 继...之后)inland by a transitional zone (过渡带)of brackish ([] 有盐味的)marsh (brackish marsh,微咸沼泽)followed by fresh-water marsh and swamp. Brackish and salt marshes are generally not areas of significant peat accumulation. Where present, these thin, marine-influenced peats tend to have a high H2S content, giving rise to pyritic (硫化铁的),high-sulfur coals.

Fresh-water marsh is a more important coal-forming environment. Large areas can be dominated by vegetation floating in shallow, stagnant ([] 停滞的，不流的)pools. These floating marsh peats thus accumulate on a root-free underclay ([] (煤层下的)底黏土层) and could be mistaken for allochthonous ([] 外来的)coals (异地煤)in the rock record. In other fresh-water marshes the rootmat of living plants is very thick with roots commonly penetrating (penetrate[] 穿入) to depths of a meter or more. The marshes grade landward ([] 向陆地)into more stable swamps, which may extend vast distances up alluvial ([] 冲积的，淤积的) lowlands toward the continental interior. Many of the thickest peats accumulate in these fresh water swamps,

and most economically important coal seams were probably of similar swamp origin.

Raised bogs (高位沼泽)may be locally important as a peat-forming environment and account for some exceptionally ([] 异常地)thick seams. These bogs are related to perched (perch,[] 栖息，位于)water tables (perched water table, 上层滞水面)and vary from moss ([] 苔藓，地衣)swamps in humid temperate ([] 气候温和的) regions to forests comprising a limited member of tree species in the tropics. Raised bogs of Borneo ([] 婆罗洲)carry dense forests with one or two tree species dominant. The peat surface is typically convex ([] 凸起的)upward with steep slopes ([] 斜坡)near the margins of the peat domes ([] 穹顶(丘)). Toward the rivers and coast the number of tree and shrub ([] 灌木)species increases before passing into coastal mangroves.

Peat growth may evolve ([] 使进化，使发展) through several stages before becoming a peat bog. Initial peat accumulation from allochthonous material or as a partially ([] 部分地)floating mat forms an island that diverts ([] 转移，转向)flow across progressively ([] 日益增多地)narrower areas of the basin. The peat becomes less frequently inundated (inundate[] 淹没)as a consequence ([] 结果)with additional water being supplied by direct precipitation ([] 降水) or by local drainage ([] 排水，排泄)into the depression ([] 低地，洼地). The rising peat surface develops its own water table and can therefore accumulate to considerable ([] 相当大的)thickness. In the case of a 33 m seam in Queensland, Australia, Smyth suggests that the final stage of peatbog (泥炭沼) formation was rapidly attained and that most of the seam accumulated in a peatbog environment. This mode of accumulation also accounts for the very low detrital mineral content and the high-inertinite ([] 惰性组)composition.

Although often difficult to reconstruct because of poor preservation ([] 保存)and mixing, the paleoecological ([] 古生态学) relationships of some ancient coal-forming plant communities have been established. These reflect a zonation into open water, marsh and swamp environments nor unlike those of today, although spanning a narrower range of adaptations ([] 适应). The fernlike (fern[] 蕨类植物) floras of the Northern Hemisphere Carboniferous ([] 石炭纪，石炭层) are poorly represented in Gondwanna ([] 冈瓦纳) deposits, which characteristically show evidence of autumnal ([] 秋天的) leaf accumulations.

Lesson Six Coal Basins

（6学时）

Tectonic ([] 构造的)setting ([] 背景，环境)influences the number, thickness, continuity ([] 连续性), and quality of seams, and determines their attitudes(attitude[] 产状), degree of disruption ([] 分裂，破裂)and present depth. This in turn determines their mineability ([] 可采性). Coal basins (煤盆地) that have been subjected to (经历，遭受)tectonic deformation with folding ([] 褶皱) and faulting ([] 断层作用) over a broad area are the most important economically. Over 90 percent of the world’s coal production comes from regions affected by late Paleozoic ([] 古生代的) and end Mesozoic ([] 中生代,中生代的)Tertiary

([] 第三纪，第三纪的)tectonism ([] 构造作用), with only a small amount from the vast, stable intracontinental (大陆的) basins such as the Moscow Basin. COAL BASINS REALATED TO SUBDUCTION ([] 俯冲作用)

Orogenic ([] 造山的) foredeeps ([] 前渊)and back-arc (弧后) basins undergo ([] 经历，遭受) locally (局部地) tight folding, thrusting (逆冲，上冲), and, where oblique ([] 倾斜的) collision ([] 碰撞，冲突) is involved, major strike-slip faulting (走向滑动断裂作用). Rapid subsidence ([] 下沉，陷落)through high geothermal ([] 地温的，地热的) gradients ([] 梯度) produces coals of subbituminous ([] 亚烟煤的) to anthracite ([] 无烟煤) rank. In areas of maximum subsidence, coals may be thick and numerous ([] 众多的，无数的) but contain large detrital splits ([] 裂开,裂口). Further, the seams commonly show a very complex three-dimensional geometry ([] 几何形态).

A modern example of a subduction-related coal basin is the southwestern foredeep of New Guinea ([] 几内亚), which is underlain by as much as 13,000 m of Cenozoic ([] 新生代，新生代的) sediments containing abundant coal seams. The Permian ([] 二叠纪，二叠纪的)Sydney Basins of Australia is remarkably similar to the New Guinea foredeep basin in geometry and inferred origin.

Coals in these orogenic ([] 造山的) basins are rapidly covered with sediment and therefore tend to be bright. Although deeply buried during tectonic subsidence (构造沉降作用), subsequent ([] 后来的，并发的)basin-edge tilting (tilt[] 使倾斜)and erosion ([] 腐蚀，侵蚀)or the onset ([] 发动，开始)of later tectonic uplift ([] 隆起，上升), elevates many seams to levels at which they can be mined without difficulty.

COAL BASINS RELATED TO EPEIROGENY ([] 造陆作用)

Intracontinental rift ([] 裂缝)grabens ([] 地堑) and strike-slip (走向滑动，走向平移)pull-apart basins (拉分盆地)can involve large vertical displacement ([] 迁移,变位), but deformation is less intense than is the case in orogenic basins. However, except in areas of persistent ([] 持久的) block faulting (块断作用) , even the most tectonically active intracontinental basins (陆内盆地)are generally subject to only moderate tectonic subsidence. Thus, the total coal-bearing succession (含煤岩系)tends to be thinner. The number of seams is limited , but their geometry and thickness are highly variable. Patterns of splitting are less complex than in the deposits of subsiding continental

([] 大陆的)margins (continental margin,大陆边缘)and the seams contain a greater proportion of dull bands because of slow burial. Many of the more rapidly subsiding epeirogenic ([] 造陆作用的) basins tend to fill with conglomeratic ([] 砾岩状的)sediments devoid of coal. Significant exceptions include the Cantabrian ([] 坎塔布连) coal basins of Spain where peats accumulated during quiescent ([] 平静的)episodes([] 时期). Lignites ([] 褐煤) of Victoria, Australia occupy a Cenozoic ([] 新生代，新生代的)aulacogen which opened to the sea, these seams are among the thickest known. STABLE CRATONIC COAL BASINS

Coal-bearing successions of cratonic basins (可拉通盆地) are normally thin and comparatively ([] 比较地，相当地)with few seams. Individual seams may, however, attain considerable thickness and some cover vast areas of 4000mi2 (10,000km2 ) and more; other seams are restricted to paleotopographic ([] 古地形的)depressions(低地，洼地), terminating abruptly against basement highs (基底高地，基底隆起).

Smyth (1980) has shown that most Australian coals thicker than 15m (50ft) accumulated in small, stable intracratonic basins subject to very gradual subsidence.

Coal-bearing successions in the intracratonic Karoo Basin change in response to elongate ([] 延长，拉长)downwarps (拗陷) in the regionally stable basement platform (地台) of Precambrian ([] 前寒武纪的)rocks. Coals are more numerous in the downwarps within which regressive ([] 海退的，回归的)deltaic ([] 三角洲的) sequences are more abundant than they are on the adjacent ([] 临近的，接近的)stable platform. Individual seams commonly split in the direction of downwarped areas. This simple pattern of interfingering (interfinger[] 指状交错)contrasts ([] 和...形成对照) with the complex splits in orogenic coal basins.

Coals of cratonic downwarps are predominantly of low to medium rank because of low geothermal gradients and limited depths of burial. The Cooper Basin of Australia with a radioactive ([] 放射性的)crystalline basement in parts (部分地,在某种程度上) provides an exception. High temperatures associated with igneous ([] 火成的) intrusion ([] 侵入)produce pockets of high-rank coal unrelated to depth. Burned coal or natural coke ([] 焦炭)forms at the intrusive contact. The generally dull nature of epeirogenic ([] 造陆作用的) basin coaks reflects prolonged exposure, responsible for the high inertinite ([] 惰性组) basin and ash content.

PASSIVE MARGIN COAL BASINS

Terrigenous ([] 陆源沉积的)clastic ([] 碎屑状的)wedges that prograde ([] 天体同向旋转的) over a progressively deepening shelf, for example the northern Gulf Coast Basin, commonly contain major coal deposits (煤藏)in the updip (上倾的，沿倾斜向上的) facies ([] 相). The coal-bearing succession can show evidence of listric ([] 铲状的) growth faulting, but the coal-bearing strata ([] stratum的复数，地层)do not as a rule display the dramatic ([] 惊人的，引人注目的)expansion characteristic of the hydrocarbon

([] 碳氢化合物，烃) bearing facies farther basinward.

EFFECTS OF CONTEMPORANEOUS ([] 同时期的,同时代的)TECTONISM ([] 构造作用)ON COAL

Contemporaneous tectonism produces dramatic changes in coal-seam thickness and petrography ([] 岩相学,岩石学). Displacement may be related to synclinal ([] 向斜的)warping ([] 扭曲，变形), graben development, or growth faulting. In parts of the Appalachian ([] 阿巴拉契亚的)Basin subsidence appears to have limited peat accumulation on the downthrown block (下降盘), whereas thick coals are located along the edge of the upthrown block (上升盘) which provided a platform for peat accumulation. Elsewhere in the Appalachian Basin in coals may thin or merge onto the upthrown block , and some coals are preserved only on the downthrown block where they survived the destructive ([] 破坏性的)effects of oxidation ([] 氧化)at higher levels. Subtle ([] 微妙的,精细的)difference in elevation of peat swamps subject to minor tectonism might be reflected in the microlithotypes(显微煤岩类型), chemistry or ash content of the coal.

CHANGES IN TECTONIC SETTING OF COAL BASINS

Coal-forming paralic ([] 近海的)environments, in which the bulk of the world’s coal resource originated, commonly precede ([] 在...之前)limnic ([] 湖泊的，湖沼的)environments during coal-basin evolution ([] 进展，发展，进化). For example, the Late Carboniferous ([] 石炭纪) foredeep north of the Variscan highlands of Europe first contained large paralic coal basins along the prograding fluvio([] 河的)-deltaic margin, followed by the limnic coals of intermontane ([] 山间的)basins. Similarly ([] 同样地，类似于), in the classical thick and relatively undeformed clastic wedges (碎屑楔状体)that result from asymmetric ([] 不均匀的,不对称的) basin filling, there may be a gradual vertical and updip progression from distal ([] 远处的) paralic to proximal ([] 最接近的)limnic coals.

Lesson Seven Basin Analysis （6学时）

SEDIMENT BODY (沉积体) GEOMETRY

The size and shape of sediment bodies is probably the most fundamental type of data utilized in basin analysis; however, it is commonly overlooked. There is value in determining the overall dimensions of the entire basins as well as the size and shape of each of the lithostratigraphic ([] 岩性地层的)units it contains. Such data are obtained through field mapping (野外绘图)and measurement of stratigraphic ([] 地层的)sections (stratigraphic section 地层剖面), logging (测井记录)of cores or other subsurface ([] 地下的)samples or from geophysical data.

It is not uncommon for the stratigraphic sequence (地层层序)in a given basin to be incomplete ([] 不完全的). That is, unconformities (unconformity[] 不一致，不整合)may be present, signifying the removal of a certain part of the rock record. These situations may cause the geologists’s job of determining the true geometry of sediment bodies to be quite difficult.

Large-scale sedimentary sequence (沉积序列)are grossly (非常，很) wedge shaped regardless of (不管，不顾)composition ([] 成分)or location. Within this overall wedge-shaped prism ([] 棱柱)of sedimentary rocks there may be several lithostratigraphic (岩性地层的)entities each of which may have its own characteristic ([] 特征的)shape (特征形状). Let us consider some general size and shape aspects of sediment bodies from various environments. At this stage (眼下，暂时)in the analysis only the gross lithology ([] 岩石学)and the geometry will be considered.

Probably the best example to use is that of quartz arenite ([] 砂岩，砂碎屑岩) with at least moderate sorting. At least four of five major depositional ([] 沉积的) environments (沉积环境)may fall within this general lithology. A tabular ([] 扁平的)or blanket sand body could indicate the shoreface (滨面)or an inland dune ([] 沙丘) field. Linear ([] 线性的，直线的)sand bodies may represent barriers([] 障碍) if they are straight or gently curved. Anastomosing patterns suggest the fluvial system. Branching or bifurcating (bifurcate[] 使分叉)linear sand bodies could develop as a tributary ([] 支流)or distributary ([] 分流，支流)system; paleocurrent ([] 古水流)direction would determine which one was present.

This is but one example of how sediment body geometry may be useful. In most cases, additional data beyond size and shape are necessary to accurately ([] 正确地，精确地)establish the particular depositional system (沉积体系)of the sediment body in question (正在被讨论的). Certainly, however, a knowledge of the size and shape of the unit will permit the geologist to exclude ([] 排除，除去)certain depositional systems from consideration and thereby enable better utilization of time in analyzing the sediment body. PROVENANCE([] 起源，出处)

Basin analysis includes more than interpreting the environment of deposition of various facies. To gain a comprehensive ([] 全面的，广泛的) understanding of the basin it is also necessary to know where the sediments came from, that is, their source rock (源岩)

type and location. The subject of this section, the provenance of the basin sediments, covers just those points. Because the basin thrust of this book is at the megascopic ([] 肉眼可见的)scale, emphasis will be those provenance characteristics that can be seen in the field with the unaided eye (肉眼)or the hand lens (简单显微镜). The reader should know that detailed provenance studies require at least petrographic ([] 岩相学的) studies, and in some cases detailed mineralogy ([] 矿物学)or trace element (微量元素)composition is required in order to trace the origin of some sediments.

For proper recognition ([] 识别)of sediment particles that might be indicative ([] 预示的，可表示的)of provenance, at least coarse sand (粗砂) is necessary. Typically, pebbles(pebble[] 小鹅卵石) and cobbles (cobble[]鹅卵石) form the basis for most provenance information in the field or at the hand lens scale. Because great detail, such as quartz types or specific mineral composition, can not be determined at this level of observation ([] 观察), one must look for readily (容易地) identifiable ([] 可确认的) and traceable detrital particles. Examples are various rock fragment ([] 片断)types, chert ([] 燧石,黑硅石)varieties, particles containing recognizable fossils, and any metallic ores (金属矿石)in large clasts ([] 碎屑岩). Any of these particles types is exotic ([] 外来的)enough to be traceable to a source rock.

One of the primary techniques that has been utilized in determining direction of ice movement by Pleistocene ([] 更新世)glaciers ([] 冰川)is through the presence of exotic rock particles which can be tied to a known source. Large clasts ([] 碎屑岩)of basaltic ([] 玄武岩的)rock with native copper (自然铜)have been found in glacial drift in southern Illinois ([] 伊利诺伊). The only source for this copper is the Keewenaw Peninsula ([] 半岛)of Michigan ([] 密歇根州). This information not only establishes the source rock type but also provides general paleocurrent direction from the source to its present location.

Coarse conglomerates ([] 砾岩)characterize the Cambrian ([] 寒武纪的)section (段,部分)in the vicinity ([] 附近，近郊) of the Baraboo (巴拉波) syncline ([] 向斜) in south central Wisconsin ([] 威斯康星州). The major rock unit that forms the syncline is a red to maroon ([] 褐红色的)Precambrian ([] 前寒武纪) quartzite ([] 石英岩). The clasts which are included in the basal ([] 基础的,基本的)Cambrian strata are clearly derived from this Baraboo Quartzite. These distinctive ([] 区别性的，鉴别性的)quartzite pebbles have been found in Cambro Ordovician ([] 奥陶纪的)strata 85km to the south, near Macison. TRENDS IN TEXTURE (组织,质地,纹理)OF SEDIMENT PARTICLES

The distribution of particle size and shape through time and space can provide substantial ([] 物质的，实质的)information that is useful in basin analysis. In general, the attempt is made to establish the existence of certain trends in the texture of particles, both geographically (地理地)and stratigraphically ([] 地层学地) . It is not textural ([] 组织上的，构造上的)properties (textural property 纹理特征)of the entire rock on which attention is focused but attribute of the individual particles, such as roundness and size.

The geographic variation ([] 变化)in grain size has received important consideration by geologists since the 1920s. Much effort has been directed toward grain size patterns in glacial drift and alluvial ([] 冲积的,淤积的)fans (alluvial fan 冲积扇). Students of F.J. Pettijohn at Johns Hopkins ([] 霍普金斯)University have done comprehensive basin analysis in the Paleozoic ([] 古生代的)strata of the Central Appalachians.

Typical efforts involve the measurement (测量)and mapping of maximum particles size and roundness, although mean pebble size may also be utilized. Increase in roundness and decrease in particle size indicates increasing distance from the source. Such trends also provide paleocurrent direction.

Stratigraphic trends (地层走向)in similar parameters ([] 参数)are also useful in basin analysis. A decrease upward in maximum clast size implies that relief ([] 地势)in the source area is decreasing, thereby decreasing the erosive power (侵蚀能力)and competence ([] 能力) of streams. On the other hand, an increase in particle size, particularly one that is abrupt stratigraphically, suggests that the source area (源区) has been rejuvenated (rejuvenate[] 使...再生); it is tectonically ([] 构造上)active. PALEOCURRENTS

A large number of sedimentary structures has directional ([] 方向的,定向的), or at least orientational ([] 方向的,方位的)properties. These structures serve as the fundamental basis for paleocurrent determinations. Actually, any feature that indicate direction of transport is a paleocurrent indicator.

Features such as cross stratification ([] 成层现象，成层作用)and bottom marks serve as the best and most abundant structures for paleocurrent determinations. Regardless of the particular directional feature(s) being used, it is necessary for the investigator to measure the spatial ([] 空间的)orientations (spatial orientation 空间定位)of many examples. It is not uncommon for paleocurrent studies to include at least several hundred directional measurements (定向测量). The field geologist (野外地质学家)must remember to adjust any directional measurements to accommodate ([] 使适应)any structural ([] 构造的)movement (structural movement构造运动)of the strata involved; this is particularly critical in foldbelt (褶皱带,造山带)areas such as the Appalachians.

Typically, paleocurrent data are portrayed (portray[] 描绘)graphically ([]图解), generally in the form of a rose diagram ([] 图表). This type of diagram is simply a histogram ([] 柱状图)plotted in such a way that direction is shown. Rather than plot the actual number of observations, it is preferable ([] 更好的,更可取的) to plot percentages. This allows comparisons ([] 比较,对照) and does not cause problems of large diagrams for some sites and small ones for others; however, one must record wide ranges in the number of observations from locality to locality ([] 位置,地点). The modal class or classes can easily be recognized in a rose diagram (玫瑰图)or current rose (流玫瑰图), as it is frequently called. A mean direction may also be calculated and shown on the diagram. It is appropriate ([] 适当的)to categorize ([] 分类)directional data for purposes of rose diagrams by stratigraphic level as well as by geographic location.

Paleocurrent directions may vary with time and therefore stratigraphic horizon ([] 地平线 ,stratigraphic horizon 地层层位), as well as with space.

Lesson Eight Principles of Applied Geophysics (应用地球物理)

（4学时）

Geophysics is the application of the principles of physics to the study of the earth. Strictly speaking the subject includes meteorology ([] 气象学), atmosphere electricity (大气电学), or ionosphere ([] 电离层)physics; but in this monograph ([] 专论)the word geophysics will be used in the more restricted sense, namely the physics of the body of the earth. The aim of pure geophysics is to deduce ([] 推论)the physical properties of the earth and its internal ([] 内部的)constitution ([] 组成) from the physical phenomena ([] 现象)associated with it, for instance the geomagnetic ([] 地磁的)field (geomagnetic field 地磁场), the heat flow (热流), the propagation ([] 传播)of seismic ([] 地震的)waves (seismic wave 地震波), the force of gravity ([] 地心引力,重力), etc. On the other hand, the object of applied geophysics, with which this monograph is concerned, is to investigate specific, relatively small-scale and shallow features which are presumed to exist within the earth’s crust (地壳). Among such features may be mentioned synclines ([] 向斜)and anticlines ([] 背斜), geological faults, salt domes ([dome] 穹丘,穹顶;salt dome 盐丘), undulations ([] 波动)of the crystalline bedrock (岩床) under a cover of moraine ([] 冰碛), ore bodies (ore body 矿体), clay deposits (粘土矿床) and so on. It is now common knowledge that the investigation of such features very often has a bearing on (have a bearing on 关系到,影响到)practical problems of oil prospecting ([] 勘探), the location of water-bearing strata (含水层), mineral exploration (矿产勘探, exploration[] 探测),highway construction and civil engineering (土木工程). Often, the application of physics, in combination with geological information, is the only satisfactory way towards a solution of these problems.

The geophysical methods used in investigating the shallow features of the earth’s crust vary in accordance with (in accordance with 与...一致) the physical properties of the rocks-the last word is used in the widest sense-of which these features are composed, but broadly speaking they fall into four classes. On the one hand are the static methods (静力法)in which the distortions ([] 扭曲,变形)of a static physical field are detected and method accurately (正确地,精确地)in order to delineate ([] 描绘) the featured producing them. The static field may be a natural field like the geomagnetic, the gravitational ([] 重力的)or the thermal ([] 热的,热量的)gradient ([] 梯度)field (thermal gradient 地温梯度), or it may be an artificially applied field like an electric potential ([] 电压)gradient (electric potential gradient 电位梯度). On the other hand, we have the dynamic methods in which signals are sent into the ground, the returning signals (回波信号)are detected, and their strengths (强度)and times of arrival (波至时间)are measured at suitable points. In the dynamic methods the dimension of time always appears in the appropriate field equations ([] 方程), either directly as the time of wave arrival, as in the seismic method, or indirectly as the frequency(频率) or phase difference (相差), as in the electromagnetic ([] 电磁场的)method. There is a further, now considerably ([] 相当地)important, class of methods which lie in between the two just mentioned. These will be called relaxation methods (松弛法). Their feature is that the dimension of time appears in them as the time needed

for a disturbed medium to return to its normal state. This class includes the overvoltage ([] 超电压) or induced polarization ([] 极化) methods (induced polarization method 激发极化法). Finally there are what we may call integrated effect methods, in which the detected signals are statistical ([] 统计学的)averages over a given area or within a given volume. The methods using radioactivity (放射能)fall in this class.

The classification of geophysical methods into ground, airborne ([] 空运的,空降的)or borehole ([] 钻孔,井孔)methods refers only to the operational procedure. It has no physical significance. Many ground methods can be used in the air, under water or in boreholes as well.

The magnetic, electromagnetic and radioactive methods have been adapted to geophysical measurements from the air. Airborne work has certain advantages. Firstly, on account of the high speed of operations an aerial ([] 航空的)survey (aerial survey 航测) is many times cheaper than an equivalent ([] 相等的,同等的)ground survey, provided the area surveyed is sufficiently large, and secondly, measurements can be made over mountains, jungles, swamps, lakes, glaciers and other terrains ([] 地形)which may be inaccessible ([] 达不到的,难以接近的)or difficult for ground surveying parties.

Compared with ground work, airborne measurements imply a decrease in resolution which means that adjacent geophysical indications tend to merge into one another giving the impression of only one indication. Besides, there is often considerable uncertainty ([] 不确定) about the position of airborne indications so that they must be confirmed on the ground before undertaking further work such as drilling (钻井).

In a sense (在某种意义上), applied geophysics, expecting the seismic methods, is predominantly (突出地,主要地)a science suited to flat or gently undulating (undulate[] 波动,起伏)terrain where the overburden ([] 覆盖层,盖层表土)is relatively thin. The reason is that whenever the relief is violent, the data of geophysical methods need corrections (校正)which are frequently such as to render their interpretation uncertain. On the other hand, when the overburden is too thick the effects produced by the features concealed ([] 隐藏)under it generally lie within the errors of measurement and are difficult to ascertain ([] 确定). There is, however, no general rule as to the suitability ([] 合适,适当) of any terrain to geophysical methods and every case must be considered carefully on its own merits. The various methods of applied geophysics will be dealt with in turn (依次,轮流)in the following chapters.

Lesson Nine General Petroleum ([] 石油)Geology

（4学时）

Petroleum ( rock-oil, from the Latin petra, rock or stone, and oleum, oil) occurs widely in the earth as gas, liquid, semisolid ([] 半固体), or solid, or in more than one of these states at a single place. Chemically any petroleum is an extremely complex mixture of hydrocarbon (碳氢化合物)(hydrogen ([] 氢)and carbon ) compounds, with minor amounts of nitrogen ([] 氮气), oxygen , and sulfur as impurities (impurity[] 杂质). Liquid petroleum, which is called crude oil (原油)to distinguish it from refined oil (精炼油), is the most important commercially. It consists chiefly of the liquid hydrocarbons, with varying amounts of dissolved gases, bitumens ([] 沥青), and impurities.

Petroleum gas, commonly called natural gas to distinguish it from manufactured gas (人造煤气), consists of the lighter paraffin ([] 石蜡)hydrocarbons, of which the most abundant is methane ([] 甲烷,沼气) gas (CH4). The semisolid and solid forms of petroleum consists of the heavy hydrocarbons and bitumens.

Because of its wide occurrence and its unique appearance and character, petroleum has always been readily (容易地)observed by man, and is repeatedly mentioned in the earliest writings of nearly every region of the earth. Oil and gas seepages ([] 渗流) and springs, and tar ([

] 焦油), asphalt ([] 沥青), or bitumen deposits of various kinds exposed at the surface of the ground, were regarded as local curiosities (curiosity[] 好奇心)and attracted visitors from great distances. From the earliest times recorded by man, petroleum is frequently mentioned as having an important part in the religious, the medical, and even the economic life of many regions. Not until after the middle of the nineteenth century, however, when it was first discovered in large quantities underground, did its potential commercial importance become apparent ([] 显然的).

Since 1900, the geology of petroleum has assumed growing importance as a special economic application of geology. From the first, geologists attempted to explain the occurrence of oil and gas in terms of (in terms of 根据,依照)geologic phenomena. Then, as the petroleum industry grew and developed, they were called in more and more to guide the programs o exploration ([] 勘探,探查)for the raw materials upon which the industry depended. New geologic concepts ([] 观念,概念) relating to petroleum were thus developed, and at the same time enormous volumes of new data were made available with which to test and prove or disprove ([] 反驳,驳斥) many established principles of geology. As a result, not only the petroleum industry, but the science of geology as a whole (as a whole 总体上), has benefited greatly.

When a petroleum pool has been discovered, we know (a) that a supply of petroleum originated in some manner, (b) that it became concentrated into a pool, and (c) that it has been preserved against loss and destruction. The evidence for the speculative ([] 推测的,推理的)theories about the geologic history of petroleum before it was discovered-its origin, migration ([] 运移,迁移), accumulation and preservation ([] 保存)-can come from a study of

the pool.

The fundamental ([] 基础的,基本的)geologic requirements for oil and gas pools are, of course, the same the world over. Whether one is exploring in the Americas, along the continental shelf (大陆架), the Middle East, or the Far East, the essential ([] 基本的,必需的) elements of a pool are simple. A porous ([] 多孔的,渗水的)and permeable body of rock (岩体), called the reservoir rock (储集岩), which is overlain by an impervious ([] 不渗水的)rock, called the roof rock (顶板岩石), contains oil or gas or both, and is deformed or obstructed (obstruct[] 妨碍,阻碍)in such a manner that the oil and gas are trapped.

Commercial deposits (有经济价值的矿床)of crude oil and natural gas are always found underground, where they nearly always occur in the water-coated pore spaces of sedimentary rocks. Being lighter than water, the gas and oil rise and are concentrated in the highest part of the container; in order to prevent their escape, the upper contact of the porous rock with an impervious cover (不透水盖层) must be concave ([] 凹的), as viewed from below. Such a container is called a trap (圈闭), and the portion of the trap that holds the pool of oil or gas is called the reservoir. The significant thing is that reservoirs can be of various shapes, sizes, origins, and rock compositions.

The actual discovery of a pool is made by the drill, but the proper location of the wildcat well (碰运气的井,野猫井)to test a trap, the depth to which it should be drilled, and the detection and outlining of the oil or gas pool from what is revealed (reveal[] 展现)by that well and others, are wholly geologic problems. They constitute the essence ([] 精髓)of the geology of petroleum and are the most important work of the petroleum geologist. He may need to consider only a simple combination of stratigraphy ([] 地层学)and structural geology (构造地质学), or he may have to take account of a complex combination of data, involving such various fields as stratigraphy, sedimentation (沉淀作用), paleontology ([] 古生物学), geologic history, fluid flow, structural geology, petrography ([] 岩石学), geophysics, geochemistry, and metamorphism ([] 变质作用). In addition to all this, he may have to draw on his own and other people’s knowledge of many related sciences, such as physics, chemistry, biology and engineering. He must do his best to work out the geology of an area from what is visible or what can be mapped at the surface, and from all available well and geophysical data for depths ranging up to three miles or more below the surface. His prediction, however, may often be based on the most fragmentary ([] 不连续的)data, some of which are obtained by specialists ([] 专家)or expects who may or may not have a working knowledge (应用知识)of geology, or by geologists who have worked with no thought of the petroleum possibilities of the region. This information is assembled on maps and cross sections (横切剖面), and fitted together (组合,结合)in the mind of the petroleum geologist, where it is interpreted (interprete [] 翻译)and translated into the best place to drill a well that will penetrate ([] ) a trap below the surface of the ground and thereby enable the well to test the traps content.

As the search for petroleum gets deeper below the surface, the geology becomes more complex and uncertain, and the data upon which the geologist must base his conclusions become progressively fewer. As drilling is costly, there are never as many test wells (测试井) as the petroleum geologist would wish. Every scrap of information must therefore be squeezed out of the

record and put to use (put to use 使用,利用), and the data from each record must be projected outward in all directions. Yet all these maps and data do not, of themselves, tell the whole story. If they are to be fully used in the discovery of petroleum, they must be interpreted, correlated (correlate[] 和...相关) and integrated.

This interpretation of the combined basic geological, geophysical, and engineering data, for the purpose of finding new oil and gas pools (gas pool 气藏), is what constitutes the special provinces of the petroleum geologist. It results, first of all, in locating an oil and gas prospect, which is the set of circumstances, both geologic and economic, that will justify ([] 证明...是正当的)the drilling of a wildcat well. The petroleum geologist’s work does not stop, however, when he has located a prospect; it continues during the drilling of the wildcat well. He must relate the new facts encouraged in the drilling to the problem of identifying ([] 识别,鉴别) and testing the potential producing formations (producing formations 产油层) and of completing the well in the producing formation if the well becomes a discovery well (见油井). The petroleum geologist thus spans the gap between geology and the related sciences, on the one hand, and the oil and gas prospect and the pool, on the other. Petroleum prospecting is an art. It requires combing (comb[] 搜寻) and blending many geologic variables ([] 变量) in varying proportions, since each pool, field, of province is characterized by a unique combination of many different geologic conditions. Some of these conditions can be known in advance, but most cannot, and the most successful geologist is the one who can visualize the pool or locate the extension with the least advance information. He may be likened to the artist who can draw the picture with the fewest lines, or to the paleontologist (古生物学家)who can identify a fossil vertebrate ([] 脊椎动物)from the least number of bones.

Lesson Ten Concept of Facies ([] 相) （4学时）

The first use of the term facies is generally attributed to Amanz Gressly, a Swiss ([] 瑞士)eologist who applied it to lateral ([] 侧面的) changes he observed within time-stratigraphic units of the Mesozoic ([] 中生代). Facies”is now somewhat broadened to include the total of both lithologic ([] 岩性的) and biologic characteristics of a stratigraphic unit (时代地层单元). It is also used in metamorphic ([] 变质的) rocks and even into biological sciences.

Beginning in the 1930s the term “facies” was used widely in classical stratigraphic studies. Applications to stratigraphy ([] 地层学) and to the analysis of the rock record were typically from either the lithologic or the paleontologic(古生物学的) point of view. The former are called lithofacies ([] 岩相) and the later are biofacies. Although such usage ([] 使用)is still proper and is still applied, there has been a more environmental and genetic use of the term in recent years. We now typically speak of “reef facies (礁相),” “delta-front facie (三角洲前缘相),” or “tidal flat facies (潮坪相).” In other words, each environment, no matter how broad or restricted in its definition, is characterized by its own facies. For example, “fluvial facies (河流相)” covers the broad spectrum (范围)of stream deposits, whereas “point-bar facies (曲流砂坝相)” is restricted to a particular sedimentary environment within the fluvial ([] 河流的)system.

The operational use of the term “facies” is therefore likely to be based on somewhat different characteristics in the modern environment than it might be in the rock record. Characteristics of, and boundaries for, a modern sedimentary environment can be rather easily established using sediment parameters, biologic attributes if any, and sedimentary structures. Also, topography ([] 地形学), water depth, and physical process can be used in describing a modern facies. By contrast, the resulting rocks have only their preservable ([] 可保存的)attributes, such as petrology ([] 岩石学), paleontology, sedimentary structures, and geometry, which geologists can use for the facies definition. It is not uncommon for sediments of adjacent ([] 邻近的,接近的)and similar modern environments to exhibit the same or very similar appearance in the rock record. For example, it is often difficult to separate the beach and adjacent nearshore ([] 近滨的)sediments in the rock records, as it may be to distinguish the fluvial from the deltaic ([] 三角洲的)facies. These potential problems provide yet another demonstration ([] 实证)of the importance of a knowledge of modern sedimentary environments to the geologists working with the rock record, either on the surface or in the subsurface ([] 地下的,表面下的).

Probably the most important single concept that must be thoroughly understood and applied by the sedimentologist ([] 沉积学家)and stratigrapher ([] 地层学家)was formulated by Johannes Walther in 1894. He stated that “only those facies and facies-areas can be superimposed (superimpose[] 重叠的,叠加的)primarily which can be observed beside each other at the present time”. Also called the Law of the Correlation (or Succession) of Facies, this fundamental principle of geology is used universally (普遍地) but without knowledge of its origin and is frequently misstated (misstate[] 谎报,伪称)

The practical use that is made of Walther’s concept is the the relationship between the lateral

distribution (横向分布)of modern sedimentary facies and the vertical succession (垂向层序)of facies in the rock record. It is common for the geologist who is examining the ancient record to experience some difficulty in interpreting depositional environments (沉积环境), due perhaps to lack of experience, absence of diagnostic ([] 特征的,有鉴定意义的)criteria (标准), or a multitude of other reasons. Perhaps one or two paleoenvironments can be recognized with some degree of certainty, but overlying and underlying ones cannot. Use of Walther’s law (瓦尔特相律)enables one to make a logical interpretation of the stratigraphic succession (地层层序). Typically, lagoons ([] 泻湖)separate barriers from the coastal plain (滨海平原), and the inner shelf (内陆架)or shoreface (临滨,滨面) is seaward of a barrier. It is axiomatic ([] 理所当然的), therefore, that the vertical succession of environments or facies must reflect these relationship (Fig.1); if it does not, the succession may contain interruptions such as the erosion of some facies.

Detailed studies of the broad spectrum of modern environments and the stratigraphic record have shown that there is a limited number of associations of lithology (岩性), structures, fossils, and so on. As a result, a number of sedimentary depositional models (沉积模式)exists which characterizes various sedimentary environments. Models of modern environments may be characterized by their lateral surficial ([] 地表的)associations, whereas emphasis on the ancient record is in the vertical sequence. Walther’s law is applied in order to properly understand the relationships between adjacent or related modern depositional systems and their counterparts (对应部分,对应物)preserved in the rock record.

In order to accumulate a vertical sequence of changing rock types, changes must have taken place which caused the spatial shifting of the sedimentary environments that produced these rocks. The shift may be accomplished, for example, by tectonic activity (构造活动性), which in turn may cause sea level to change, or which may cause the relief ([] 地势) to change; it may be caused by glacial activity (冰川活动), which can also change sea level and change climate, or by any other phenomena which will cause sedimentary environments to be displaced in space during time.

An association ([] 组合,联合)of environments which is useful as an illustration ([] 图解,说明)is found along the marine coast and related shelf. Commonly, a coastal plain is bounded by a lagoon or estuary ([] 河口湾), barrier island (障壁岛), nearshore, and shelf environments as one proceeds seaward. A major change in sea level will cause these environments to shift in response to the moving shoreline. Two basic situations exist: progradation ([] 进积)(regression []海退) as the shoreline moves seaward or retrogradation ([n] 退积) (transgression [] 海侵,海进) as the shoreline moves landward. Most discussions on this topic center around transgression and regression, with sea level implied as rising in the former and being lowered in the latter. Another equally important consideration in the environment of the shoreline is the amount of sediment being transported to the coast. It is not uncommon for coastal deposits to build seaward or prograde during rising sea level, such as in a delta or in some barrier islands. As a result, “transgression” will be used in this text to refer to the situation of landward movement of the shoreline and “prograndation” will be used in reference to the seaward migration of the shoreline. In either case the vertical succession of environments or facies shows those environments which are geographically adjacent to be stratigraphically adjacent. The sequence will be reversed

(reverse [] 颠倒,翻转)but the relationships are the same (Fig.2). In a progradational situation the shallow water or the landward environments are on the top of sequence, and in a retrogradational (海退的)or transgressive (海侵的)sequence the deeper-water environments are on top at a given locality.

Depositional systems that are not coastal or marine undergo similar shifts, which result in similar sequences. For the most part the commonly preserved sequence is a progradational situation where one environment migrates over another. For example, in an arid region of at least moderate relief, one might find playa ([] 干盐湖)lake deposits over which dunes have migrated and an alluvial fan might cover the dunes. Again, environments which are geographically juxtaposed (juxtapose [] 并列)become vertically arranged in the stratigraphic record (地层记录)at a given locality.

A prograding marine model contains all those environments mentioned above and more. In addition to the textural and mineralogical ([] 矿物学的)parameters of the sediment, one must consider sedimentary structures (沉积构造), sediment body geometry, and biogenic ([] 源于生物的)constituents. This example represents the general types of successions that may be encountered in the rock record and also the criteria that are used to characterize them. It should be observed that these examples are general ones; many others have been formulated. In examining stratigraphic sequences for features that will be of value in environmental reconstruction (环境的再造), the geologist should utilize all the data available.

Lesson Eleven Characteristics of the Delta System （5学时）

The delta is comprised of a diverse complex of depositional environments that span a wide range from terrestrial ([] 陆地的)through coastal to purely marine. The processes and resulting morphology ([] 形态学) of a delta are the result of a great variety of interdependent factors. Although there is a considerable range in the specific characteristics among the world’s deltas, they also share some general features and processes that are universal ([] 普遍的)regardless of size or location of the deltaic system.

Deltas can typically be subdivided into three broad environments: the delta plain, which is largely subaerial ([] 地表的)but contains subaqueous ([] 水中的,水下用的)portions, the delta front (三角洲前缘), and the prodelta ([] 前三角洲).There is a general seaward fining of sediment particle size within the latter two regions of the delta. The distal ([] 远端的,末端的) portion of the delta (prodelta) is dominated by clays settling from suspension (沉淀,沉积).

Whereas one commonly thinks of deltas in terms of large accumulation of sediment and as constructional ([] 建设的,堆积的)systems, there is typically a destructional ([] 破坏的,侵蚀的) phase as well. Erosion may actually dominate at some areas or during certain periods of time when little sediment is being supplied. Waves and currents, both wave generated and tidal, are the primary agents of erosion on the delta. The destructive ([] 破坏性的)phase dominates on abandoned (已废弃的)portions of the delta when sediment influx ([] 注入,流入)

from the river has ceased. The active delta is dominated by the constructional phase. Beaches, beach ridges (滩脊), and dunes may develop along the shore of the abandoned delta, whereas the active delta exhibits progradation ([] 进积)of the deltaic plain, with greatest rates concentrated at the major distributaries (distributary[] 分流,支流).

Deltaic Processes

Knowledge of sedimentary processes associated with the development of deltas has only recently approached the level of that for delta morphology ([] 形态学)and stratigraphy (形态学). Beginning in the 1950s and continuing to the present, much effort has been expended (expend []消费,支出)in understanding the complexities of deltaic processes, which are complicated by the interaction of riverine ([] 河流的)processes with those of the marine environment.

A number of processes shares control over delta development and maintenance ([] 维持,保养). Some of these operate on, or adjacent to, the delta and others may be geographically remote from the delta itself. Among the latter are climate, relief in the drainage ([] 排水)basin (drainage basin 集水区), sediment yield (沉积量), and the water discharge ([] 放出,释放)regime ([] 状态,情况). In some respects (在某些方面)climate may be the most influential of all the processes that affect deltas. It controls not only the amount and temporal ([] 时间的)distribution of water discharge but also the vegetation, weathering, and soil development, and to some extent, the

relief in the drainage basin. Obviously ([] 明显地), the latter factors strongly influence the nature and volume of sediment discharged through the river mouth (河口).

Riverine Processes

For initial purposes of discussion it is best to consider the relatively simple river mouth situation, where tides are negligible ([] 可以忽略的)and wave power is minimal ([] 最小的). These circumstances result in a river-dominated situation such as occurs in lakes, estuaries, enclosed seas (内海), or where there are broad, flat, offshore slopes (滨外坡). Under these conditions three primary forces dominate: inertia ([] 惯性), bed friction ([] 摩擦力), and buoyancy ([] 浮力,浮性). Factors such as discharge, outflow velocity ([] 速度), water depth, size and amount of particles in the sediment load (输沙量), and the density ([] 密度)contrast between the river and basin waters determine which of the three forces controls the riverine processes on the delta.

(a) Inertia-dominated effluent

High outflow velocities, deep water immediately seaward of the river mouth, and negligible density contrasts give rise to dominance by inertial forces (惯性力), causing the effluent ([]) to spread and diffuse ([] 扩散)as a turbulent ([ ] 紊流的,湍流的)jet ([] 喷射,射流) (turbulent jet 紊流,湍流). This turbulent mass of sediment-laden (含沙量大的,携带大量泥沙的)water is termed; that is, there is a uniformity ([] 均一性)in density between the effluent ([] 测流)and the ambient ([] 周围的)water body. Such a situation represents the simplest conditions of river mouth sedimentation and was the basis for Gilbert’s classic deltaic model with topset ([] 顶积层),foreset ([] 前积层), and bottomset (底积层)components. These conditions are generally restricted to high gradient (梯度)streams entering a deep lake or where tidal activity homogenizes ([] 使均一)the water masses (水团), thereby destroying any density gradients.

The primary sediment body is a lunate ([] 新月形的)bar (砂坝), convex ([] 凸起的)seaward, with the coarsest sediment particles located landward of the bar crest ([crest] 顶部). Low spreading angles (spreading angles 展角)of the turbulent jet restrict the lateral dispersion ([] 散射,分散)of sediment particles. The relief on the bar is low and a relatively steep bar front is developed. Laboratory experiments have substantiated (substantiate [] 证明,证实)this model from the two-dimensional point of view.

(b) Bed friction-dominated out flow

In many river mouth environments, continual ([] 连续的,持续不断的)discharge of sediment causes substantial shoaling ([] 使变浅)just beyond the mouth; in fact, it is common that depths in this area are a maximum of slightly less than in the outlet ([] 出口). The result is a lateral spreading of the effluent as a plane jet (水平射流)accompanied by shear ([] 剪切,剪力)between the outflow and the bottom with

significant frictional ([] 摩擦的)effects. This is also a type of homopycnal ([] 等密度的)flow (等密度流), but requires only that density contrasts be eliminated (eliminate[] 除去)by marine processes (e.g., tides, waves, currents).

As outflow occurs there is shoaling, but in this situation the lateral spreading is enhanced by the friction-induced deceleration ([ ] 减速). This in turn increases the shoaling rate and results in a divergence ([] 分散,离散)or bifurcation ([] 分叉)of the outflow, causing formation of a middle ground bar.

Most of the major rivers flow into marine waters. The density of fresh water is essentially 1.00g/cm3, whereas that of seawater is typically 1.026 to 1.028g/ cm3. Even though these rivers carry a significant sediment load (输沙量)in suspension ([] 悬浮体), the density of the sediment-laden water is rarely at or above the density of seawater. The result is that the river outflow “floats” on the ambient seawater due to the density contrast. This is called hypopycnal flow (等密度流). Strong tidal influence and mixing caused by wave or current action may decrease this buoyant effect so that it is dominated by inertial ([] 惯性的)or bottom friction flow. In rivers with high discharge rates or during flood stages (洪峰)of some rivers when outflow is strong, the buoyant effect is prominent ([] 卓越的,显著的). Rivers that experience small tides typically are characterized by a stratified (stratify[] 使成层)circulation. Such is the case for the Mississippi, the Danube ([] 多瑙河)(Romania [] 罗马尼亚)), and the Po ([] 波河) (Italy) Rivers.

Convergence ([s] 汇聚,收敛)of flow near the bottom results in sediment accumulation in the form of straight subaqueous ([] 水中的,水下用的)levees ([] 天然堤). A distributary-mouth bar (分流河口砂坝)accumulates about four to six channel ([] 渠道)widths to seaward. Due to flow convergence, the coarsest particles are restricted to a narrow region, As the distributary-mouth area progrades, these bar sands develop into the bar-finger sands (指状砂). Particle size decreases seaward down the distal front of the bar.

Marine Processes

In virtually ([] 实质上,事实上)all river mouth environments there is a complicated interaction ([] 交互作用)between the riverine processes described above and those of the basin into which the river debouches (debouch[] 流出). Although here these are called marine processes, with the exception of tides they also apply to rivers entering nonmarine water bodies. (a) Tides

Several of the major deltas in the world are either strongly influenced or are dominated by tidal activity (潮汐活动). Although only the Amazon ([] 亚马逊河)falls into that category for the western hemisphere, the Ganges-Brahmaputra (Bangladesh [] 孟加拉) and the Ord ( Australia ) are but two of several deltas that experience severe modification by tides.

The role of tides in river mouth processes is essentially threefold ([] 三倍):

1.Mixing destroys density gradients and negates ([] 否定)effects of buoyancy (浮力).

2.During low discharge periods tides may be the dominant sedimentation processes.

3.The zone of marine-riverine interaction is extended in range, especially horizontally ([] 水平地).

Tidal dominance is marked by a distinctly bi-directional (双向作用的)nature to the processes, which is reflected in the sediment bodies accumulating seaward of the river mouth. The most common morphology ([] 形态学)is a system of linear shoals (浅谈) with their long axes parallel to flow.

In tide-dominated rivers the channel widens markedly near the mouth, forming a bell-shaped configuration ([] 外形)(Fig.3). Because of the relatively strong tidal currents (潮流), this zone is generally sand filled. Marked meandering ([] 曲流作用)with related point-bar deposits is common upstream ([] 上游)from the bell-shaped channel near the mouth.

(b) Waves

Typically, deltas are not well developed or are not present at all along coasts with a rigorous ([] 严密的,精确的)wave climate (波候). There is a general relationship between broad, gently sloping shelves, low wave energy, and well-developed deltas. Some deltas do, however, develop on steep nearshore ([] 近滨的)slopes under high-wave-energy conditions.

As waves approach and impact on the active delta they cause a spreading and deceleration ([ ] 减速)of the effluent. Riverine outflow interacts with waves, causing them to break in abnormally deep water. This has the effect of abruptly decreasing the competence of the outflow and causes sediment to accumulate closer to the river mouth than under low-wave-energy conditions. This sediment accumulation is in the form of a crescentic ([] 新月形的)river mouth bar and subaqueous levees upon which swash ([] 冲洗,冲刷) bars develop. This river mouth sediment body configuration is typically for waves that approach normal to the shore.

Although shallow currents may be generated by wind, waves, tides, or deep ocean currents impinging (impinge[] 冲击,碰撞) on the continental ([] 大陆的) margin, their net effect on deltaic sedimentation is generally to modify river mouth morphology in a shore-parallel ([] 平行的)direction. These currents typically display an alongshore ([ ]近岸)component, and it is this aspect ([] 方面)that markedly affects river mouth sedimentation. Undoubtedly, the most prominent of these currents is the wave-generated longshore (沿岸的)current which results from refraction ([] 折射)in shallow water.

Even though there may be a wide range in the direction of these currents through time at a given location, there is typically a dominant direction. It is this current direction that is responsible for the river mouth morphology. The most common modification is the formation of a spit ([spit]

沙嘴,岬)and accompanying channel mouth migration.

Lesson Twelve Porosity ([] 孔隙度,孔隙率)and Permeability([] 渗透率) （6学时）

While it is true that geologists study rocks, much applied geology is concerned with the study of holes within rocks. This is of vital importance both in the search for oil, gas and ground water (地下水), and in locating regional permeability barriers which control the entrapment ([] 圈闭) and precipitation of low temperature ore minerals (金属矿物). A sedimentary rock is composed of grains, matrix (基质), cement (胶结物)and pores (孔隙)(Fig.7). The grains are the detrital ([] 碎屑的) particles which generally form the framework of a sediment. Matrix is the finer detritus ([ ] 岩屑,碎屑)which occurs within the framework. There is no arbitrary size distinction between grains and matrix. Conglomerates ([] 砾岩)generally have a matrix of sand, and sandstones may have a matrix of silt and clay. Cement is post-depositional (沉积后的)mineral growth which occurs within the voids of a sediment. Pores are the hollow spaces not occupied by grains, matrix or cement. Pores may contain gases, such as nitrogen and carbon dioxide, or hydrocarbons such as methane ([] 甲烷). Pores may be filled by liquids ranging from potable ([] 可饮用的)water to brine ([brain] 盐水)and oil. Undersuitable conditions of temperature and pressure, pores may be filled by combinations of liquid and gas. The porosity of a rock is the ratio of its total pore space to its total volume, i.e. for a given sample: porosity=total volume－bulk volume. Conventionally porosity is expressed as a percentage. Hence:

Porosity= volume of total pore space ×100

Volume of rock sample

The porosity of rocks range from effectively zero in unfractured cherts ([] 燧石,黑硅石)

to, theoretically, 100% if the “sample” is taken in a cave. Typically porosities in sediments range between 5-25%, porosities of 25-35% are regarded as excellent if found in an aquifer ([] 含水层)or oil reservoir (油藏).

An important distinction ([] 区别,差别)must be made between the total porosity (总孔隙度) of a rock and its effective porosity (有效孔隙度). Effective porosity is the amount of mutually interconnected ([] 互相连接)pore spaces present in a rock. It is, of course, the effective porosity which is generally economically important, and it is effective porosity which is determined by many, but not all, methods of porosity measurement (孔隙度测定).

It is the presence of effective porosity which gives a rock the property of permeability ([] 渗透性). Permeability is the ability of a liquid or gas to flow through a porous ([] 多孔隙的,多孔状的)solid. Permeability is controlled by many variables([] 可变的). These include the effective porosity of the rock, the geometry ([] 几何形态)of the pores, including their tortuosity ([] 弯曲,变曲度), and the size of the throats between pores, the capillary force between the rock and the invading fluid, it s viscosity ([] 粘度,粘性)and pressure gradient.

Permeability is conventionally determined from Darcy’s law using the equation

([] 方程式):

Q= K△A μL

where Q is the rate of flow in cm3/s, △ is the pressure gradient, A is the cross-sectional area,μis the fluid viscosity in centipoises ([] 百分之一泊, 粘滞性单位), L is the length and K is the permeability.

This relationship was originally discovered by H. Darcy in 1856 following a study of the springs of Dijion. Permeability is usually expressed in darcy ([] 达西)units, a term proposed and defined by Wycoff et al. in 1934. One darcy is the permeability which allows a fluid of one centipoises viscosity to flow at one centimeter per second, given a pressure gradient of one atmosphere per centimeter.

The permeability of most rocks is considerably ([] 相当地)less than one darcy. Two avoid fractions ([] 分数)or decimals, the millidarcy is generally used, being onethousandth of a darcy. The permeability of rocks is highly variable, both depending on the direction of measurement and vertically up or down sections. Permeabilities ranging from 10 to 100 millidarcies are good and above that are considered exceptionally high. Primary or Depositional Porosity 沉积期孔隙度

Primary or depositional porosity is that which, by definition, forms when a sediment is laid down. Two main types of primary porosity may be recognized.

(a) intergranular ([] 粒间的)porosity 粒间孔隙度

Intergranular or interparticle porosity occurs in the spaces between the detrital ([] 碎屑的)grains which forms the framework of a sediment. This is a very important porosity type. It is present initially([] 最初地)in almost all sedimentary rocks. Intergranular porosity is generally progressively reduced by diagenesis ([] 成岩作用,岩化作用)in many carbonates ([] 碳酸盐), but is the dominant porosity type found in sandstones.

(b) Intraparticle([] 粒内的)porosity 粒内孔隙度

In carbonate sands, particularly those of skeletal ([] 骸骨的)origin, primary porosity may be present within the detrital grains. For example, the cavities ([] 洞穴)of mollusks ([] 软体动物), ammonites ([] 菊石,干肉粉), corals, bryozoa ([] 苔藓虫门)and microfossils may all be classed as intraparticle primary porosity (Fig.8).

This kind of porosity is often diminished shortly after deposition by infiltrating ([] 渗透)micrite ([] 泥晶灰岩,微晶灰岩)matrix ([] 基质). Furthermore, the chemical instability ([] 不稳定性)of the carbonate host grains often leads to their intraparticle pores being modified or obliterated ([] 删除)by subsequent ([] 随后的)diagenesis.

Secondary or Post-depositional Porosity

Secondary porosity is that which, by definition, formed after a sediment was deposited. Secondary porosity is more diverse ([] 不同的,变化多的)in morphology ([] 形态学)and more complex in genesis than primary porosity. The

following main types of secondary porosity are recognizable (Fig.9).

(a) Intercrystalline ([] 晶间的)porosity 晶间的孔隙

度

Intercrystalline porosity occurs between the individual crystals of a crystalline rock. It is, therefore, the typical porosity type of the igneous ([] 火成的)and high-grade metamorphic([] 变质的)rocks, and of some evaporates ([] 蒸发岩). Strictly speaking, such porosity is of primary origin. It is, however, most characteristic of carbonates which have undergone crystallization and is particularly important in recrystallized dolomites. Such rocks are sometimes very important oil reservoirs.

(b) Fenestral ([] 窗格状)porosity 格状孔隙度

The term “fenestral” porosity was first proposed by Tebbut et al.(1965) for a “primary or penecontemporaneous ([] 准同期的) gap (裂隙) in rock framework ([] 框架), larger than grain-supported interstices ([] 空隙,裂缝)” This porosity type is typical of carbonates. It occurs in fragmental ([] 由颗粒支撑的)carbonate sands, where it grades into primary porosity, but is most characteristic of pellet ([] 球粒,团粒)muds and homogenous ([] 均质的)muds (均质灰泥)of lagoonal and intertidal ([] 潮间带的)origin.

Molds are pores formed by the solution of primary depositional grains generally subsequent to some cementation. Typically in any one rock it is all the grains of one particular type that are dissolved. Hence one may talk of oomoldic pelmoldic or biomoldic porosity where there has been selective solution of ooliths ([] 鲕穴状的), pellets or skeletal debris. The geometry and effective porosity and permeability of moldic porosity can thus be extremely varied.

(d) Vuggy porosity 孔洞孔隙度

Vugs are a second type of pore formed by solution and, like molds, they are typically found in carbonates. Vugs differ from molds though because they cross-cut the primary depositional fabric ([] 构造)of the rock. Vugs thus tend to be larger than molds. They are often lined by a selvedge ([] 布的织边,镶边)of crystals. With increasing size vugs grade into what is loosely termed cavernous ([] 似巨穴的)porosity (穴管状孔隙度). (e) Fracture porosity 裂缝孔隙度

The last main type of pore to be considered is that which occurs within fractures. Fractures occur in many kinds of rocks other than sediments. Fracturing, in the sense of a breaking of depositional lamination ([] 分层,纹理)can occur penecontemporaneously with sedimentation. This often takes the form of microfaulting (微断层)caused by slumping ([] 滑动沉陷), sliding and compaction. Fractures in plastic sediments are instantaneously ([] 即刻的) sealed. In brittle rocks, however, fractures may remain open after formation, thus giving rise to fracture porosity. This porosity type characterizes rocks which are strongly lithified ([] 使岩化)and is, therefore, generally formed later in time than the other varieties of porosity.

It is important to note that many sedimentary rocks contain more than one type of pore

([] 孔隙). The combination of open fractures with another pore type is of particular significance. Fine-grained rocks, both shales, microcrystalline ([] 微晶的)carbonates and fine sands, have considerable porosity. They often have very low permeabilities. The presence of fractures, however, can enable such rocks to yield up their contained fluids. The success of many oil and water wells in such formation often depends on whether they happen to penetrate ([] 穿入)an open fracture.

Lesson Thirteen The Reservoir Rocks （5学时）

By far the most important types of reservoir rocks are the sandstones and carbonates Thus, one survey has shown that about 59% of the production from the world’s major oilfields comes from “sandstones” and 40% from “carbonates”—these terms being loosely used to include, on the one hand, orthoquartzites (正石英岩), greywackes ([] 杂砂岩), arkoses ([] 长石砂岩)and conglomerates ([] 砾岩), and on the other precipitated[] carbonates, muddy limestones, reef limestones, and many kinds of dolomites ([] 白云岩). Other rocks also occasionally provide petroleum reservoirs, but these occurrences ([] 发生,出现,赋存)are relatively rare; they include various igneous and metamorphic rocks, fractured shales and cherts.

Sandstone Reservoir Rocks

Sandstones result from the breakdown of the so-called crystalline rocks as a result of weathering, following by transport and eventual deposition of the comparatively ([] 比较地)large resultant ([] 产生结果的,有效果的)particles, or from similar actions on previously formed sandstones. They are formed of grains of quartz, possibly embedded (embed [] 使嵌入)in a matrix of finer particles, with varying proportions of cementing ([] 胶结,粘合)material.

The terms ”sand” or “pay sand” are often used in oilfield parlance ([] 说法,用语)to describe an oil-saturated ([] 使饱和,充满)sandstone, although completely uncemented sands are rare. When a poorly-cemented sandstone is in fact an oil or gas reservoir, problems usually arise as a result of sand being carried into the well-bore during production. Such an unconsolidated ([] 未固结的)sand may have over 40% porosity, depending on the degree of rounding and size distribution of the individual particles and the manner of packing. The presence of cement automatically reduces the porosity, and extensive cement deposition ([] 沉积作用,沉积物)may reduce the porosity to less than 10%, with a relatively much greater reduction in the permeability. However, the effect of cement deposition on effective porosity and permeability is complex.

Furthermore, for geometrically similar grains and grain arrangements ([] 安排,排列), and hence, geometrically similar pore spaces, the permeability is proportional to the square of the characteristic grain size. Deposition of mineral matter in the pore spaces causes a reduction in porosity directly proportional to the amount deposited, whereas even when this mineral matter is uniformly ([] 均一地)distributed the relative reduction in permeability is decidedly ([] 明显地)greater.

When there are clay partings on the bedding planes of a sandstone, they will have little effect on the permeability of the sandstone parallel to the bedding planes, but they will markedly reduce the permeability in a direction normal to the bedding planes. Small discontinuous ([] 不连续的,间断的)partings or wisps of clay will have comparable ([] 可比较的)although somewhat smaller effects on the permeability across the bedding, and in this case a small sample used for making permeability measurements normal to the bedding will give a lower value than for the rock in bulk, when the

parting extends right across the sample.

Deep burial with the resultant increase in pressure may lead to the fracturing ([] 破裂,断裂)of rock grains and some rearrangement to give increased packing density and a lower porosity. This is particularly noticeable in areas of great thickness of relatively soft Tertiary ([] 第三纪)strata, as in the USA Gulf Coast area. If the initial porosity of a sandstone was say 35%, it will probably be reduced to 25% when the rock has been subjected to a pressure of about 20,000 psi—equivalent ([] 相等的,相当的)to burial to about 18,000 ft.

Rise in temperature associated with increased pressure will result in a general deterioration ([] 变质,退化)of porosity and permeability in a sandstone. In addition to the effect already mentioned, there may be pressure solution at grain contacts, the growth of quartz grains at the expense of the matrix material, or the development of stylolites ([] 缝合岩面)with the consequent ([] 作为结果的,随之发生的)segregation ([] 分凝,分凝作用)of insoluble ([] 不能溶解的)clayey material along planes normal to the direction of the pressure (commonly, therefore, along bedding planes, for simple burial effects).

In the foregoing ([] 前述的,上述的), the ultimate ([] 最后的,最终的)concern has been with the holes in the rock—their sizes, shapes and interconnections [], for these determine the porosity, permeability and capillary pressure. However, study of the size and shape of the constituent ([] 组成,成分)particles, which is feasible by the use of drill cuttings, supplemented ([] 补充,增补)in some cases by examination of the so-called sedimentary structures seen in cores, makes it possible to determine the environment of deposition, i.e. Whether the sand is Aeolian ([] 风神), fluvial or marine in origin. Such determinations may be a guide to gross reservoir behaviour, and to the possibility of other prospects existing in the area.

Carbonate Reservoir Rocks

Carbonate reservoir rocks are particularly important in the Middle East area, where many of the world’s largest oilfields occur. The rocks vary from nearly pure calcitic limestones (CaCO3) to mixtures of calcite with different proportions of dolomite-CaMg (CO3)2. (A dolomite rock is usually defined as a limestone containing at least 50% of the mineral ([] 矿物)dolomite.) Limestones are nearly always of biochemical origin, being formed either through the agency of lime-secreting organisms ([] 生物体,有机体) and the accumulation of “bioclastic” shell material, or as a consequence of the precipitation of calcium carbonate from solution; in both cases there is often admixture ([] 混合物)of the calcium carbonate with other sedimentary materials, to give a wide range of “impure” limestones containing varying proportions of clay, iron oxides, etc. Normally, massive marine limestones do not contain many macro- ([] 巨大的,大量的)fossils; they are largely made up of the remains of algae ([] 海藻), with biochemically precipitated calcite. Where no organic ([] 有机的)remains at all are visible, the limestone would appear originally to have been chemically precipitated as a “lime mud”.

Limestones tend to be lower in porosity and permeability than sandstones, and particular units can be quite irregular in the distribution of these properties. Fractures, when present, commonly

affect the reservoir properties of limestones more than is the case for sandstones. The size, shape and distribution of the pores in limestones range from fairly uniform to extremely heterogeneous ([] 非均质的), even when the rock is of a single type; this contrasts ([] 比较)with the common fair degree of uniformity which exists in a homogeneous ([]均一的)sand body. In limestones, the porosity is largely inter-particle, but intra-particle and other types of porosity may be important. Post-depositional changes can affect the original porosity markedly; porosity may be created, obliterated, or extensively modified by solution, cementation, recrystallisation or dolomitisation ([] 白云石化作用).

Dolomite can be primary or secondary in origin, and it must be recognized that only when dolomitisation is a secondary process and takes place on a rigid framework can the increases in porosity calculated for the calcite-dolomite transformation ([] 转变,变化)be claimed to have been effective.

Secondary porosity and permeability in limestones can be produced by the solvent ([] 溶解的)action of meteoric ([] 大气的,流星的)waters containing dissolved atmospheric ([] 大气的)carbon dioxide. Uplift ([] 举起,升起)and exposure of limestones can afford an opportunity for such action, and it is believed to have produced the good reservoir properties found in some limestone oilfields. The effects may be limited to the top few tens of feet in some limestones; in other instances, however, thickness of several hundred feet of rock may be affected. Calcite is much more soluble ([] 可溶解的)than dolomite, so a mixed carbonate rock subjected to atmospheric weathering and solution process may develop “cavernous ([] 洞穴状的)” secondary porosity.

Carbon dioxide produced bacterially or otherwise from the subsurface ([] 地下的,地面下的)breakdown of organic matter may also be instrumental ([] 有作用的,有帮助的)in dissolving parts of limestones. In such cases, surface exposure may not be involved.

Many prolific ([] 多产的,丰富的)oilfields occur in rocks with high fracture permeability, the unfractured rock having relatively poor oil—or gas—producing characteristics. Indeed, within a single reservoir there can be marked changes in the productivity ([] 生产能力)associated with the non-uniform distribution of the fractures. An example is the significance of fracture porosity in the important Asmari limestone reservoir rocks of Iran ([] 伊朗).

Lesson Fourteen Sedimentary Organic Matter

（4学时）

Organic matter (有机质)is usually a minor constituent ([] 成分,组分) in most sedimentary rocks. However, it is present in varying amounts, in all types of sediment. Organic material is recognized in high concentrations as coal and peat deposits, as accumulation of petroleum, natural gas, tar sands and as oil-shale deposits. Most significantly, it is found in greatest abundance as finely dispersed discrete ([] 分离的,不连续的)organic particles in clastic sediments.

Sedimentary organic matter can originate from a variety of different source materials, including aquatic ([] 水生的)and terrestrial ([] 陆生的)animals. Because it either represents, or is derived from, the remains of living organisms, it is considered as fossil material.

The preservation of organic matter is almost exclusively restricted to aquaticsediments. Marine and freshwater plankton ([] 浮游生物)and bacteria which are, and have been throughout ([] 贯穿) earth history, the major producers of organic matter, also account for most of the fossil organic matter preserved in sediments.

Scientists are frequently surprised to discover that more than 98% of organic matter in sediments in the form of amorphous ([] 非晶态的,无定形的)insoluble material. Such organic matter is usually named “kerogen ([] 油母页岩)”. This term (Greek: keros meaning wax-or oil-forming and the root-gen, meaning “that which produces”) was originally proposed by Crum-Brown to describe the organic matter present in the Lothian ([] 洛锡安县)(Scotland) oil shales, which when heated produced a waxy ([] 蜡制的) -distillate ([] 馏出物). More recently the term has been applied more generally; Durand recommends[] that kerogen be defined as “the fraction ([] 小部分)of sedimentary organic matter which is insoluble ([] 不能溶解的)in the usual organic solvents”. This definition, therefore includes organic matter in humic ([] 腐殖的)coals of different ranks(humus []腐殖质, peat [] 泥炭, lignite [] 褐煤, bituminous [] 含沥青的coals, anthracite [] 无烟煤), boghead coal, cannel ([] 蚀煤)coal, asphaltoid ([] 沥青类的)substances(asphaltenes[] 沥青烯, bitumens ([] 沥青), tar in tar sands), organic matter in recent sediments soils. This author considers this definition to be too general and all encompassing ([] 包罗万象的). A major weakness in this classification is that in order to obtain kerogen concentrates ([] 集中,浓缩)from rocks, they require treatment with various mineral acids (and sometimes bases). So the accepted method of kerogen preparation(HCI, HF treatment) immediately modifies the above definition.

Some workers appear to use the term kerogen for the total organic matter in rocks. Such usage ([] 使用,用法)is considered incorrect since it is argued that the organic fraction extractable ([] 可提取的,可萃取的)with organic solvents is distinct ([] 清楚的,明显的)from and should not be grouped with kerogen but called EOM(extractable organic matter). The author considers the definition: “The disseminated ([] 散布,浸染)organic matter of rocks that is insoluble in non-oxidising mineral acids, bases and organic solvents” is currently a better definition for kerogen. Such a

geochemical definition include the insoluble palynological ([] 孢粉学的)components ([] 成分)(pollen [] 花粉, spores[] 孢子and similar organisms ([] 有机体), and allows these to be classified independently from the amorphous ([] 非晶态的)and partially structured kerogen components.

The author is in full agreement with Durand that the term kerogen should have no inferred genetic significance either concerning the origin of the constituents in the sedimentary organic matter or even from the viewpoint of postulated ([] 假定,假设)hydrocarbon generation products.

Petroleum is generally accepted to have been generated from source rocks containing organic matter originating from biological materials. The origin of petroleum can be described as a series of successive ([] 连续的), inter-related processes: (a) accumulation ([] 积聚)and preservation of organic-rich, fine-grained sediments(source rocks); (b) organic maturation ([] 煤化作用)(thermal alteration) of such organic matter, during burial with transformation into petroleum-like products; (c) expulsion ([] 驱逐,开除)of oil(and/or gas) from the fine-grained source rocks and transport within these rocks(termed primary migration); (d) movement of petroleum after expulsion from the source rocks, through the wider pores and more permeable ([] 可渗透的)and porous ([] 多孔的)carried and reservoir rocks(called secondary migration); and (e) accumulation secondary migration, in, permeable porous reservoir rocks in a trap.

Production of organic matter is the first stage in the incorporation ([] 结合,混合)of organic matter into sediments to form potential source rocks. Photosynthesis ([] 光合作用)is the most fundamental biochemical ([] 生物化学的)process which produces the precursors ([] 先驱)of the sedimentary organic matter. Solar ([] 太阳的)energy enters the biological cycle through photosynthetic ([] 光合的)production of organic, such as algae, bacteria, fungi ([] 真菌)and higher land plants. Currently, terrestrial plants and marine phytoplankton ([] 浮游植物)produce about equal quantities of organic carbon.

Terrestrial organic matter is most common along continental margins, especially in areas of major river run off. Marine organic matter production is controlled by light, temperature and nutrient ([] 有营养的)content of seawater. Areas of upwelling ([] 上升流)of deep ocean water correlate ([] 和...相关)closely with areas of high, marine organic productivity. Such areas overlay [] some of the richest potential source beds currently being deposited ([] 堆积,沉淀)on the eastern side of oceans.

Sediments often contain allochthonous [] organic matter that has been transported to the area of sedimentation from elsewhere, but they usually contain autochthonous material originating at the place of sedimentation. Autochthonous organic matter is often closely related to specific biological materials whilst ([] 同时,当...时候)the allochthonous portion may contain diagenetically ([] 成岩作用地)altered organic debris and reworked materials which probably represents the more stable components of organic matter

that have in part already passed through the geochemical cycle. Changes in composition of sedimentary organic matter is a function of the evolutionary ([] 进化的)origin of the organic matter, time and temperature. Older sediments contain only remnants ([] 残余，剩余)diageneticalof primitive ([] 原始的,简单的)organisms and the older the sediment the more consistent ([] 一致的,相容的)will be the chemical composition of the sedimentary organic matter.

Accumulation of organic matter into sediments ultimately depends upon “equilibrium” ([] 平衡,均衡)process which not only preserve and concentrate ([] 集中,浓缩), but also degrade and dilute ([] 冲淡)the organic matter. It is estimated ([] 估计,评价)that less than about one present of the organic matter produced within the biochemical cycle is finally incorporated ([] 合并,混合)into sediments. The bulk of the organic matter is preserved in detrital anoxic ([] 缺氧的)environments.

Accumulation of organic-rich sediments can be due to one or a combination of (a) high productivity, (b) high preservation, (c) low dilution ([] 稀释).

In order to have good oil source rocks, it is important to identify ([] 识别,鉴别)sediments that contain significant amounts of marine phytoplankton ([] 浮游植物), which contain abundant lipid-organic ([] 油脂) material.

The critical factor related to accumulation of sedimentary organic matter is the development of anoxic environments(aquatic ([] 水生的)environments depleted ([] 弄空,耗尽) in oxygen; where virtually all aerobic ([] 需氧的) biological activity has ceased ([] 停止) . Biochemical evidence suggests that potential organic-rich source rocks are and have been deposited in four main anoxic environments: large anoxic lakes (e.g. Late Tanganyika ([] ); Eocene ([] 第三纪下层)Green River Formation); anoxic silled ([] 岩床,煤层底板)basins(e.g. Black Sea, Baltic ([] 波罗的海)Sea, Lower Jurassic ([] 侏罗纪)(Toarcian) of the Paris Basin); anoxic layers caused by upwelling (e.g. coastlines of California ([] 加利福尼亚), Peru ([] 秘鲁), Chile ([] 智利), Western Australia, South-West Africa, Tertiary ([] 第三纪)of California); open-ocean anoxic layers (e.g. Indian ([] 印度的)ocean, Gulf of California, Atlantic Ocean, widespread occurrence ([] 出现,发生)of organicrich black shales during the Late Jurassic and Middle Cretaceous ([] 白垩纪).

Lesson Fifteen Sequence Stratigraphy [] 地层学（3学时）

As the search for oil and gas becomes more sophisticated ([] 复杂的,尖端的)and producing basins and fields become more intensely developed, geoscientists ([] 地球学家)need correspondingly more accurate ([] 精确的)techniques for stratigraphic ([] 地层学的)analysis. To achieve this accuracy, companies are shooting higher resolution seismic lines, acquiring 3-D seismic surveys over fields and coring more to quantify ([] 用数量表示,量化)reservoir properties. Exploration ([] 探测，勘探)and production staff, provided with these more accurate but expensive data , often underutilize the well log. In basins or fields with a sufficient ([] 足够的)density of well control, the coupling ([] 连合,结合)of conventional well logs and cores with the techniques of sequence stratigraphy results in an ultra-high-resolution chronostratigraphic(年代地层的)framework for subsurface correlation. Where integrated with seismic and biostratigraphic ([] 生物地层的)data, well-log cross sections, interpreted using sequence and parasequence concepts provide a state-of-the-art (发展现状)framework for analyzing reservoir, source and seal distribution whether on a regional or a field-reservoir scale.

Sequence stratigraphy is the study of genetically ([] 遗传地)related facies within a framework of chronostratigraphically significant surfaces. The sequence is the fundamental stratal ([] 地层的)unit for sequence-stratigraphic analysis. The sequence is defined as a relatively conformable, genetically related succession ([] 层序)of strata bounded by unconformities (不整合面)or their correlative ([] 相关的，关联的)conformities ([] 一致,符合,遵守). Sequence boundaries form in an increase in water depth. Parasequences and parasequence sets are building blocks of sequences. A parasequence (层内层序)is defined as a relatively conformable, genetically related succession of beds or bedsets bounded by marine-flooding surfaces or their correlative surfaces.

A parasequence set is defined as a succession of genetically related parasequences that form a distinctive stacking ([] 叠加,堆放)pattern, bounded, in many cases, by major marine-flooding surfaces and their correlative surfaces. Parasequences and parasequence set boundaries form in response to an increase in water depth. Under certain depositional conditions, parasequence and parasequence set boundaries may coincide ([] 与...相符)with sequence boundaries. Parasequences are composed of bedsets, beds, laminasets ([] 纹层,薄层)and laminae.

These strata units, ranging from the sequence down to the lamina ([] 纹层), are the building blocks of sedimentary rocks; they form a stratigraphic hierarchy ([] 层次,层级,级别)and share two fundamental properties: (1) each stratal unit, with a exception of the lamina, is a genetically related succession of strata bounded by chronostratigraphically ([] 年代地层的)significant surfaces, and (2) each surface is a single, physical boundary that everywhere separates all of the strata above from all of the strata below over the extent of the surface.

Because of these properties, bounding surfaces that are correlated using well logs, cores, or outcrops ([] 露头), provide a high-resolution chronostratigraphic framework for

facies analysis. Vertical facies analysis must be done within conformable ([] 适合的,一致的)stratal ([] 地层的) packages to accurately interpret coeval ([] 同时代的,同时期的), lateral ([] 侧面的,横向的)facies relationships along a single depositional surface. Parasequence, parasequence set, and sequence boundaries, occurring with a high frequence in siliciclastic (硅质碎屑的)sections, are significant deopositional discontinuities; in most places, the facies above these boundaries have no physical or temporal ([] 时间的)relationship to the facies below. Because of this decoupling ([] 减弱震波)of facies across these boundaries, vertical facies analysis should be done within the context ([] 上下文,前后关系)of parasequences, parasequence sets, and sequences to interpret lateral facies relationships accurately.

Using well logs, cores or outcrops, each sequence can be subdivided into stratal units called systems tracts, based on their positions within the sequence, the distribution of parasequence sets and facies associations. Systems tracts are defined as a “linkage ([] 连接)of contemporaneous ([] 同时期的,同时代的)depositional systems”. Systems tracts provide a high degree of facies predictability within the chronostratigraphic framework of sequence boundaries. This predictability is especially important for the analysis of reservoir, source, and seal facies within a basin or a field.

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地质专业英语-讲稿08