地質(zhì)學(xué)基礎(chǔ)-地質(zhì)構(gòu)造

1、Chapter 4 Geological Structure 第四章 地質(zhì)構(gòu)造,§2-1 geological time and Chronological scale地質(zhì)年代與地質(zhì)年代表,一、Geological Time Geological time is a method of ordering and measuring past events. The or

2、dering of events uses a group of observational methods known as: 1 Absolute dating methods(絕對(duì)年代法) 2 Relative dating methods（相對(duì)年代法）,1 Absolute dating methods,Absolute dating methods are those that generate an ag

3、e in years. There are two principal methods: one is the method which rely on event in the geological record with very strong annual cyclicity(周期性), such as tree growth rings ,coral growth cycles varves（紋層） (annual clay

4、sediment layers). Another Methods is more commonly used now days which rely on the decay of naturally occurring radiogenic isotopes:,Radiometric dating is not without difficulties but is by far the most widespread method

5、 applied to determine absolute ages between 100 and 4500 My. Uranium(鈾), Thorium（釷） and Potassium （鉀）are by far the most common radiogenic isotopes in the Earth's crust. Radiocarbon is important in dating organi

6、c remains from the relatively recent past.,2 relative dating methods,Relative dating methods use geological principles to place events in chronological order.which include: ? strata superposition method（地層層序法） ? foss

7、il succession method（化石演變法） ? the method of rock layers contact relation （巖層接觸關(guān)系法）.,?The principle of superposition states that older beds are covered by younger beds. In other word, the youngest unit is usually at

8、 the top in a sedimentary sequence.,?The principle of fossil succession states that organisms evolve through time so that particular forms can be used as age markers wherever they are found.,? The method of rock layers

9、contact relation states that the contact relations among rock layers is the history records of crust movement, magma activities. So geological events can be ordered by the relation of rock layers , these includes ：,① t

10、he relations among sedimentary rock , （沉積巖之間的接觸關(guān)系）② the relations among the igneous rock,（巖漿巖之間的接觸關(guān)系）③ the relation between sedimentary rock and igneous rock.（沉積巖和巖漿巖之間的接觸關(guān)系）,① The relations among sediment

11、ary rockThe relations among sedimentary rock can be divided into： conformity （整合） Unconformity（不整合）. The conformity means that strata was formed in a stable sedimentary environment, the dip and strike o

12、f strata are basically the same.,conformity （整合接觸關(guān)系）,Unconformity（不整合）.,The unconformity mean there is a break in sedimentation, a period of erosion or an episode of deformation, Unconformities range from minor erosiona

13、l breaks to strong angular discordances in bedding. An unconformity indicates a period where no rock record is accumulated. They are time-breaks of indeterminate length.,整合接觸,平行不整合 接 觸,角度不整合 接 觸,② the relations am

14、ong the igneous rock,,巖漿巖之間的接觸關(guān)系,Cross-cutting relationships among igneous rocks indicate that intrusion rocks must be younger than the rocks they cut.,③ the relation between sedimentary rock and igneous rock.,Cro

15、ss-cutting relationships between igneous rocks and sedimentary rock Indicate that sedimentary rock included pebbles and fragments must be older than the host rock containing them.,二、Chronological scale,The geologic time

16、 scale was originally a set of relative dates but the various eons（宙）, eras（代）, periods（紀(jì)） and epochs（世） have now been accurately dated with the aid of radiometric methods. The important dates are: 4,600 My - the age o

17、f the Earth and Solar System 3,600 My - the earliest life 570 My - the first appearance of abundant and varied organic forms 200 My - the break-up of the super continent 66 My - the disappearance of the din

18、osaurs,多么富有想象力的比喻！,§2-2 Basic shape and classification of geological structure 地質(zhì)構(gòu)造的基本形態(tài)和分類,一、intruduction Geological structure is the study of the permanent deformation and rock fai

19、lure created by the changes in stress through geologic time. It is by far the most important aspect of geology for the engineer to understand. Tectonic構(gòu)造 processes are responsible for the many discontinuity planes （不連續(xù)面）

20、(fractures裂隙, faults斷層, joints節(jié)理) that permeate rock masses controlling their strength, stress-strain characteristics and the transmission and storage of fluids.,Structures may be conveniently subdivided into two groups:

21、 brittle structures 脆性構(gòu)造 recording the brittle-elastic failure彈脆性破壞 of rocks in the past. Faults and joints fall in this broad category. ductile structures 柔性構(gòu)造 preserving the permanent viscoplastic

22、（粘塑性） deformation of rock throughout geologic time. Folds and metamorphic foliations are the expression of this type of structure.,The most striking features of rocks as engineering materials is that they ar

23、e not simple, isotropic各向同性的, elastic and continuous but very complex, strongly anisotropic各向異性的, anelastic粘彈性 discontinuous. It is virtually impossible to deduce the stress history of rocks from their observed deformati

24、on. There are always many ambiguou不明確的 deformation paths路徑 that could have been followed to produce what is observed.,The study of structure involves the careful recording of the orientation of lines and planes in rock m

25、asses in order to deduce the three-dimensional geometry of the distorted變形的 crust.,二、spacial state of strata(地層的產(chǎn)狀要素),Planes can be defined in space by their inclination or dip and their strike, the bearing of the line o

26、f intersection of the plane and a horizontal surface. Notice that the bearing of the projection of the dip on a horizontal surface is in a direction at right angles to the strike. This is called the dip direction.,Dip ：傾

27、角Dip direction： 傾向Strike：走向,三、水平構(gòu)造和單斜構(gòu)造(Horizontal and inclined structure ),,,Horizontal structure,Inclined structure,三、Folding,The definition of folding （褶皺的定義） Folds result from the plastic deformation of r

28、ocks at low strain-rates, usually under elevated temperature and pressure conditions. 2 The shape description （形態(tài)描述） Folds are broadly subdivided into anticlines背斜 (upwards convex凸的) and synclines向斜 (downwards

29、 convex,In synclines and anticlines, the axial plane is the plane of symmetry passing through the apex （頂點(diǎn)）of the fold. The line of intersection of the fold apex and the horizontal plane is called the axis of the fold.,軸

30、面,Pivot 樞紐,翼部,翼部,向斜,背斜,,3 the classification of folding,(1) According to the Orientation of axial plane The orientation of the axial plane relative to the horizontal together with the orientation of fold limbs翼部 al

31、low subdivision into upright (axial plane vertical, limbs symmetric), overturned (axial plane moderately inclined, one limb overturned), or recumbent 平臥的(axial plane near horizontal, one limb inverted).,（2）according to p

32、ivot location state,Horizontal fold,Inclined fold,（3）According to the tightness of folding,The tighness of folds can be described as open (limbs dip gently), tight (limbs dip steeply) or isoclinal (limbs are parallel).,四

33、 、Fracturing structure斷裂構(gòu)造,,Fracture plane,1 Jointing節(jié)理,（1） The definition of Jointing Joints are discontinuities on which there has been little or no displacement in shear (in contrast to faults). Joints are ubiq

34、uitous (普遍存在的)in igneous, metamorphic and sedimentary rocks. They are evidence of brittle failure of the rock mass at some stage in the deformation history.,◆ joints in igneous rock Joints in igneous rocks are often a

35、ssociated with the tensile stresses generated by shrinkage as the rock cools. The joints form normal (at right angles) to the cooling surface. The margins of lava flows, sills（巖床）, dykes （巖墻）and plutons（侵入體） commonly for

36、m the cooling surfaces.,（2） the formation of joints,,巖漿巖中的節(jié)理構(gòu)造,◆ Joints caused by crust movement,a: Joints in Compressive Stress Fields In compression, joints develop in the conjugate共軛的 shear directions (the orient

37、ation of symmetric fracture planes) making the lower angle with the major principal stress direction. Shear joints are often groooved, striated有條紋的, polished or slickensided（有光面的） by even small amounts of shear displacem

38、ent.,,,b: Joints in Tensile Stress Fields In tension, joints develop by stretching normal to the tensile stress direction which is usually the minor principal stress. Tension joints are rough (unless subsequently w

39、eathered). In coarse grained rocks such surfaces may be very rough.,,,C Joints in Folding Several sets of joints may develop in response to folding. Conjugate shear joints oblique傾斜的 to the fold axis are develpoed by

40、 compression. Tension joints can develop due to bending, particularly in the vicinity of the fold hinge（樞紐）. Joints parallel to the strike of the fold axis are called strike joints; those parallel to the limb dip are kno

41、wn as dip joints. Such joints are generally tensile fractures.,Joints have many important properties as planes of weakness in rock masses: ▼ Orientation 產(chǎn)狀 - strike and dip or dip and dip-direction. ▼ Spacing間距

42、 - the frequency or number of discontinuities per unit length.,（3） the features of joints,▼ Aperture（口徑，） - the mean distance between wall rock surfaces. ▼ Persistence（連續(xù)性） - the continuity of joints

43、or trace length. ▼ Surface Roughness粗糙度 - the property controlling friction between surfaces. ▼ Infill充填 - the presence or absence of breccia角礫, or surface coatings of minerals.,Joints and other discontinui

44、ties such as faults, cleavage（解理，劈理）, metamorphic foliation（葉理，面理）, and bedding planes control many important properties of rock masses including: Strength, Compressibility, Permeability. evaluation methods ste

45、p 1 to choose the representative place step 2. Measuring, and making statistics table of jointsstep 3. making the joint rose flower map,（4） The engineering meaning and evaluation of joints

46、,joint rose flower map,N,W,E,0,90,10,20,（1） the definition of faulting Faults are planar discontinuity surfaces along which there has been significant displacement in shear. In common with all planar structures, a faul

47、t has a strike and dip.,2 Faulting 斷層,（2）the description of shape 斷層的形態(tài)要素,? According to the direction of relative movement of the two blocks,Faults are divided into:,（3）Fault Types,Normal Faul 正斷層Reverse Fault

48、 逆斷層 Strike-slip Fault 平推斷層,Normal FaultIn normal faulting, the hanging wall block moves down relative to the footwall block. The fault plane usually makes a high angle with the surface (> 45 degrees). Normal

49、faults are associated with tension.,Normal Fault,Reverse Fault In reverse faulting, the hanging wall block moves up relative to the footwall block. The fault plane usually makes a low angle with the surface (< 45 de

50、grees). Reverse faults are associated with crustal compression and are also known as thrust faults.,Reverse Fault,Strike-slip Fault In strike-slip faulting, the two blocks move either to the left (sinistral ) or to the

51、right (dextral) relative to one another. Strike-slip faults are associated with crustal shear and are also known as wrench faults(扭性).,Strike-slip Fault,? According to the stress condition of fault happening,Faul

52、ts of different types are charcteristic of the stress field in which they formed. Faults are nothing more than failure of the crust in shear. The crust is generally in a triaxial state of stress with three principal stre

53、ss directions, one vertical and two horizontal.,,In normal faulting, the largest (most compressive) stress is vertical. The smallest and intermediate stresses are horizontal.,Tension faulting,In reverse faulting, the sma

54、llest (least compressive) stress is vertical. The largest and intermediate stresses are horizontal.,Compressive faulting,In strike-slip faulting, the intermediate stress（中間主應(yīng)力） is vertical. The largest and smallest stres

55、ses are horizontal.,Shear faulting,斷層組合分類,傾向不同的正斷層形成地塹,傾向相同的正斷層形成地壘,傾向相同的逆斷層形成疊瓦狀構(gòu)造,五 、地質(zhì)構(gòu)造在地質(zhì)圖中的表現(xiàn)形式,斷層切割褶皺后在地質(zhì)圖中的表現(xiàn)規(guī)律,①②③④⑤⑥⑦⑧⑨●??◆?◇▼????★,This image shows San Andreas Lake and Crystal Springs reservoir from t

56、he air, looking South East from here， The highway paralleling the lakes to the left is Interstate 280 the most beautiful urban highway in the United States''. (And it is indeed very scenic.),,,,,,,,,,,,,,根據(jù)軸面產(chǎn)狀對(duì)