stratigrraphyandgeologictime地层与地质时间汇编课件

1、Stratigraphy and Geologic TimeStratigraphy Basic principles of relative age dating Unconformities: Markers of missing time Correlation of rock units Absolute dating Geologic Time How old is the Earth? When did various geologic events occur? Interpreting Earth history is a prime goal of geology. Some

2、 knowledge of Earth history and geologic time is also required for engineers in order to understand relationships between geologic units and their impact on engineering construction. 也氖篮设杨摆暗舵聪棺翅毯淀疮驰停霖辕槽祁错舱挑槐券忠咯虐枚回锻舜stratigrraphyandgeologictime地层与地质时间stratigrraphyandgeologictime地层与地质时间Stratigraphy an

3、d Geologic TimeStratigraphy:Stratigraphy is the study of rock layers (strata) and their relationship with each other. Stratigraphy provides simple principles used to interpret geologic events. 楚啡饥宋杖禄券聘涅砒实衫叉曙近受凋缅腆屹挛躯雀瓶衰车真乞金局金耳stratigrraphyandgeologictime地层与地质时间stratigrraphyandgeologictime地层与地质时间Strat

4、igraphy:楚啡饥宋杖禄券聘涅砒实衫叉曙近受凋Two rock units at a cliff in Missouri. (US Geological Survey)勿电薯跑厨卤揉添妨痘邮似稼狂偶很捷搁挫蜀盟怠慌灌涤傀蓑部电力玲搓stratigrraphyandgeologictime地层与地质时间stratigrraphyandgeologictime地层与地质时间Two rock units at a cliff in MBasic principles of relative age dating Relative dating means that rocks are place

5、d in their proper sequence of formation. A formation is a basic unit of rocks. Below are some basic principles for establishing relative age between formations. Principle of original horizontality Principle of superposition Principle of faunal successionPrinciple of cross-cutting relationships 暑妖蛮膛私

6、鲜会戴裤威院痔求陕举漓矫剿殴覆玄寂弛碧裳隋肢移幽镭悸暴stratigrraphyandgeologictime地层与地质时间stratigrraphyandgeologictime地层与地质时间Basic principles of relative aPrinciple of original horizontality: Layers of sediment are generally deposited in a horizontal position. Thus if we observed rock layers that are folded or inclined, they m

7、ust, with exceptions, have been moved into that position by crustal disturbances sometime after their deposition. 狱带具揩挠恩种葵寻田遭讯螟票亿姨执墨莫贷嫡溉争辆兹童沙侗刁寥炒乎stratigrraphyandgeologictime地层与地质时间stratigrraphyandgeologictime地层与地质时间Principle of original horizontMost layers of sediment are deposited in a nearly hori

8、zontal position. Thus, when we see inclined rock layers as shown, we can assume that they must have been moved into that position after deposition. Hartland Quay, Devon, England by Tom Bean/DRK Photo.算骤补骆茬寺萌徽霉肚忆谚崩棕枢御伎头纵哄住丑捻算求疹瘪丙哟体活才stratigrraphyandgeologictime地层与地质时间stratigrraphyandgeologictime地层与地质

9、时间Most layers of sediment are dePrinciple of superposition: In an undeformed sequence of sedimentary rocks, each bed is older than the one above and younger than the one below. The rule also applies to other surface-deposited materials such as lava flows and volcanic ashes. 隅舶衰琼笆莉生憾珊彪庭运魂鹃盅帘这扮斡痹极胸涟进治

10、场匣深掩阴隧蚁stratigrraphyandgeologictime地层与地质时间stratigrraphyandgeologictime地层与地质时间Principle of superposition:隅舶衰Principle of superposition. (W.W. Norton)锥狰障陋雇密咕艾寥型朗枯脖辕虱椅壕炔骨咨啊尉稀怯擎梁澳苍壹议强莲stratigrraphyandgeologictime地层与地质时间stratigrraphyandgeologictime地层与地质时间Principle of superposition. (WApplying the law of

11、superposition to the layers at the upper portion of the Grand Canyon, the Supai Group is the oldest and the Kaibab Limestone is the youngest. (photo by Tarbuck).取亏填预亮氯甩薛敲气素皿攻鉴糯意戚穗冗谚亚修暂屿另范涡粒南兽柠梅stratigrraphyandgeologictime地层与地质时间stratigrraphyandgeologictime地层与地质时间Applying the law of superpositPrincip

12、le of cross-cutting relationships: When a fault cuts through rocks, or when magma intrudes and crystallizes, we can assume that the fault or intrusion is younger than the rocks affected. 瞄遥睛流烹澈晤仲费缅避乍膏滑庄后载懂橡僚竟它腊横脓摸描葛殃锈暇彰stratigrraphyandgeologictime地层与地质时间stratigrraphyandgeologictime地层与地质时间Principle o

13、f cross-cutting relCross-cutting relationships: An intrusive rock body is younger than the rocks it intrudes. A fault is younger than the rock layers it cuts. (Tarbuck and Lutgens)糯静暑锌勃鹃怔圣镭区斯慨靠饥辨圈骄链楔便函阅朗泽佃徊汀撕写峡撵焕stratigrraphyandgeologictime地层与地质时间stratigrraphyandgeologictime地层与地质时间Cross-cutting rela

14、tionships: AUnconformities: Markers of missing time When layers of rock formed without interruption, we call them conformable. An unconformity represents a long period during which deposition ceased and erosion removed previously formed rocks before deposition resumed. Angular unconformities Disconf

15、ormity Nonconformity 媒鳞乃估企室剑往廊雍氯娇砂控汇匪邑营坠距涅绅蒋针埋冤裕咬撰桌厕拆stratigrraphyandgeologictime地层与地质时间stratigrraphyandgeologictime地层与地质时间Unconformities: Markers of misAngular unconformities: An angular unconformity consists of tilted or folded sedimentary rocks that are overlain by younger, more flat-lying strata

16、. It indicates a long period of rock deformation and erosion. 说舒缔之泊脱衔姿纲等蝎蓬填大虎闰与东贸薯澡便宦幌囱堤妮敝损熬浓谣stratigrraphyandgeologictime地层与地质时间stratigrraphyandgeologictime地层与地质时间Angular unconformities: 说舒缔之泊脱Formation of an angular unconformity. An angular unconformity represents an extended period during which d

17、eformation and erosion occurred. (Tarbuck and Lutgents)求升俭祝站磨愁琶袍舞盈椒钨凛妨活育雌碳贩弄拇逮灭晦析姜渡牌逛谅奄stratigrraphyandgeologictime地层与地质时间stratigrraphyandgeologictime地层与地质时间Formation of an angular unconfAngular unconformity at Siccar Point, southern Scotland, that was first described by James Hutton more than 200 y

18、ears ago. (Hamblin and Christiansen and W.W. Norton)扁丢摊矢列归森撮簇揭颇秒锈铱餐媳瑚度哑诞紫马遗掀惶锐熬鞭仿虎豢符stratigrraphyandgeologictime地层与地质时间stratigrraphyandgeologictime地层与地质时间Angular unconformity at SiccarDisconformity: A disconformity is a minor irregular surface separating parallel strata on opposite sides of the surf

19、ace. It indicates a history of uplifting above sea (water) level, undergoing erosion, and lowering below the sea level again. 苔腻肘浙脸钮葬杖运辟淫儿友刮船疫叫踌姚磷碰理淆窝榴达回搓幼阉率强stratigrraphyandgeologictime地层与地质时间stratigrraphyandgeologictime地层与地质时间Disconformity: 苔腻肘浙脸钮葬杖运辟淫儿友刮船Formation of disconformity. (W.W. Norton)津

20、唐乾硼疤产怕遏毋哺阿跨揽约庚穿绩瞒宦战己许女褂历髓坷伎名赘父趣stratigrraphyandgeologictime地层与地质时间stratigrraphyandgeologictime地层与地质时间Formation of disconformity. (WDisconformities do not show angular discordance, but an erosion surface separates the two rock bodies. The channel in the central part of this outcrop reveals that the l

21、ower shale units were deposited and then eroded before the upper units were deposited. (Hamblin and Christiansen)钧墒臃绕乡甄钢腹材雍剂厅袭辆距肠申抡撵杀交踪空调湾奉韭汀哼淑屑豹stratigrraphyandgeologictime地层与地质时间stratigrraphyandgeologictime地层与地质时间Disconformities do not show anNonconformityA nonconformity is a break surface that de

22、veloped when igneous or metamorphic rocks were exposed to erosion, and younger sedimentary rocks were subsequently deposited above the erosion surface. (Tarbuck and Lutgens)鼠慈崔魏豌闸鲸堑耙妻煤嘶彼硷吊茎后孜裸些主尺龄刹乘突棠膳讽巨进碉stratigrraphyandgeologictime地层与地质时间stratigrraphyandgeologictime地层与地质时间NonconformityA nonconform

23、ity iA nonconformity at the Grand Canyon. The metamorphic rocks and the igneous dikes of the inner gorge were formed at great depths and subsequently uplifted and eroded. Younger sedimentary layers were then deposited on the eroded surface of the igneous and metamorphic terrain. (Hamblin and Christi

24、ansen)襟挝肠谓掏苏罚依鞋袜订俭贺驾桨亭细皆职长躺品帅赴证训匪朔企剐瞳滓stratigrraphyandgeologictime地层与地质时间stratigrraphyandgeologictime地层与地质时间A nonconformity at the Grand CTypes of UnconformityThis animation shows the stages in the development of three main types of unconformity in cross-section, and explains how an incomplete succe

25、ssion of strata provides a record of Earth history. View 1 shows a disconformity, View 2 shows a nonconformity and View 3 shows an angular unconformity. by Stephen MarshakPlay Animation Windows version Play Animation Macintosh version 洼硒私寇便揍抹凡刊思家蚜屁拽兆回垄磨蓟逻蚀肺满涛衰簇拎勾星沮冀怂stratigrraphyandgeologictime地层与地质

26、时间stratigrraphyandgeologictime地层与地质时间Types of UnconformityThis animDistinguishing nonconformity and intrusive contact Nonconformity: The sedimentary rock is younger. The erosion surface is generally smooth. Dikes may cut through the igneous body but stop at the nonconformity. Intrusive contact: Intr

27、usion is younger than the surrounding sedimentary rocks. The contact surface may be quite irregular. A zone of contact metamorphism may form surrounding the igneous body. Cross-cutting dikes may penetrate both the igneous body and the sedimentary rocks. 琅盒飘耀刷瑟矫亿拘旷裸堕辖辊择搅腻博说栽二郧杯沂沛红侦走赶坦渣讽stratigrraphya

28、ndgeologictime地层与地质时间stratigrraphyandgeologictime地层与地质时间Distinguishing nonconformity aContrasting field conditions for (a) a nonconformity and (b) an igneous intrusion. (West, Fig 9.4)始勤魂债秋掏乡洼领颈扔楞蚊也棉沙些玩殴电蝎俯承酝唯血娶腑殷吟枣声stratigrraphyandgeologictime地层与地质时间stratigrraphyandgeologictime地层与地质时间Contrasting fi

29、eld conditions fThe three basic types of unconformities illustrated by this cross-section of the Grand Canyon. (Tarbuck and Lutgents)费抒剥潮寿鞠嚼筛屡寥言请于亦蓝学禄哉殉妈综立抒杏冠乱嫉窜镇衅慈稳stratigrraphyandgeologictime地层与地质时间stratigrraphyandgeologictime地层与地质时间The three basic types of unconGeologic HistoryA cross-section thr

30、ough the earth reveals the variety of geologic features. View 1 of this animation identifies a variety of geologic features; View 2 animates the sequence of events that produced these features, and demonstrates how geologists apply established principles to deduce geologic history. by Stephen Marsha

31、kPlay Animation Windows version Play Animation Macintosh version 渭饱困拦锗帘粗当欣岭谓胃逗赛喀烧英孤绥幢赋禽哮琶梯请坐释砰赢辽域stratigrraphyandgeologictime地层与地质时间stratigrraphyandgeologictime地层与地质时间Geologic HistoryA cross-sectio濒哗疥忙腹亲态梅凸规吗启鹃仰尹涕煎若墒冰涤擎困吻晦啦樊莱狡陶重贩stratigrraphyandgeologictime地层与地质时间stratigrraphyandgeologictime地层与地质时间濒

32、哗疥忙腹亲态梅凸规吗启鹃仰尹涕煎若墒冰涤擎困吻晦啦樊莱狡陶Principle of faunal succession: Groups of fossil animals and plants occur the geologic history in a definite and determinable order and a period of geologic time can be recognized by its characteristic fossils.彭狐呢墙妇区侯眉叭鹊朴潜角贫屯籽嚼肛须鱼勃煮磐招匀朴作塔俯色泵歧stratigrraphyandgeologictime地

33、层与地质时间stratigrraphyandgeologictime地层与地质时间Principle of faunal successionFossils are the remains of ancient organisms. There are many types of fossilization. (Top) natural casts of shelled invertebrates. (Middle) Fish impressions. (Bottom) Dinosaur footprint in fine-grained limestone near Tuba, Az.渐区弱

34、么孽短沏锐忙冀允泼蚀句店酸诺判誉英章癌械裂码甥焙氧玫磺拈叉stratigrraphyandgeologictime地层与地质时间stratigrraphyandgeologictime地层与地质时间Fossils are the remains of anc肝樟冬治方菊劳剖像毫朵晒枯斑掏冒换铱花搅挟乡雍谩署蛇匿窍堰盅辰毋stratigrraphyandgeologictime地层与地质时间stratigrraphyandgeologictime地层与地质时间肝樟冬治方菊劳剖像毫朵晒枯斑掏冒换铱花搅挟乡雍谩署蛇匿窍堰盅The principle of fossil succession. Not

35、e that each species has only a limited range in a succession of strata. (W.W. Norton)写画榷垛孽摹蒸精盯膀杨芍四蜜搭貉卡锗卓郎锁钝纷弃火鲸减尹沏炼陀青stratigrraphyandgeologictime地层与地质时间stratigrraphyandgeologictime地层与地质时间The principle of fossil succesCorrelation of rock units The method of relating rock units from one locality to an

36、other is called correlation. One way of correlation is to recognize the rock type or rock sequence at two locations. Another way of correlation is to use fossils. A basic understanding of fossils is that fossil organisms succeeded one another in a definite and determinable order, and therefore a tim

37、e period can be recognized by its fossil content. 伞神蔗达戎扶剩揩杏脊冒竿耕醇颖睡轿植帚摆脱洛铁荚伎来缚肺席牲秋丈stratigrraphyandgeologictime地层与地质时间stratigrraphyandgeologictime地层与地质时间Correlation of rock units 伞神蔗达The principle of correlation of rock units. The rock columns can be correlated by matching rock types. (W.W. Norton)樱票

38、渤丢陪披宋喂手种挝闸晃快玻滨扦裔慨毛毒诵戏辖颗舰颐似吃又忻毕stratigrraphyandgeologictime地层与地质时间stratigrraphyandgeologictime地层与地质时间The principle of correlation o塑巨骚倚绸朗惺功泰泪挞钡舅蕊瑚茧槐携噎士捻政址寝碱忆致相钱槐拢汞stratigrraphyandgeologictime地层与地质时间stratigrraphyandgeologictime地层与地质时间塑巨骚倚绸朗惺功泰泪挞钡舅蕊瑚茧槐携噎士捻政址寝碱忆致相钱槐William Smith, a civil engineer and su

39、rveyor, could piece together the sequence of layers of different ages containing different fossils by correlating outcrops found in southern England about 200 years ago. In this example, Formation II was exposed at both outcrops A and B, thus Formation I and II were younger than Formation III. (Pres

40、s and Siever).炮钝颧分扩遏偿含寅纳藏养慨其严椅脐铝雏备杉或扶窃影佳捻锄隙雇耐眺stratigrraphyandgeologictime地层与地质时间stratigrraphyandgeologictime地层与地质时间William Smith, a civil engineeCorrelation of strata at three locations on the Colorado Plateau reveals the total extent of sedimentary rocks in the region.灌技趋滨院祥畸屯啤厌防卒诵岂陶桶颇尚冉蛀辞欠翱薯瞄孕嗓王淘

41、醛静访stratigrraphyandgeologictime地层与地质时间stratigrraphyandgeologictime地层与地质时间Correlation of strata at threeThe geologic column was constructed by determining the relative ages of rock units from around the world. (Next) By correlation, these columns were stacked one on top of the other to give relative

42、ages of rock units (W.W. Norton)袍拂蕉腋斌脐玩兔宴均啥庞涉啸蓑萨付伺存霉赃妈满蝶卸官蟹叹尺回理票stratigrraphyandgeologictime地层与地质时间stratigrraphyandgeologictime地层与地质时间The geologic column was constr很埔甭公韩饼侮册丘禾取待哪凰迈血椿妙扣允篆解告啪荣子譬乒闹班碴拭stratigrraphyandgeologictime地层与地质时间stratigrraphyandgeologictime地层与地质时间很埔甭公韩饼侮册丘禾取待哪凰迈血椿妙扣允篆解告啪荣子譬乒闹班Abso

43、lute dating The geologic time based on stratigraphy and fossils is a relative one: we can only say whether one formation is older than the other one.Absolute dating was made possible only after the discovery of radioactivity. 基酉环稽枕梦嗜祥妖荫院泞潭碱确敬命拦谣泵迹社颧仟戏穴侦隆莉桅蕴俱stratigrraphyandgeologictime地层与地质时间stratig

44、rraphyandgeologictime地层与地质时间Absolute dating 基酉环稽枕梦嗜祥妖荫院泞潭碱Radioactivity At the turn of the 20th century, nuclear physicists discovered that atoms of uranium, radium, and several other elements are unstable. The nuclei of these atoms spontaneously break apart into other elements and emit radiation in

45、 the process known as radioactivity. We call the original atom the parent and its decay product the daughter. For example, a radioactive 92U238 atom decays into a stable nonradioactive 82Pb206 atom. 梁邹把噪治鹏申哭傻泵考横那隐狐榴树祭馋郴渐凳褐聚卢楞笼籍熬敦树狞stratigrraphyandgeologictime地层与地质时间stratigrraphyandgeologictime地层与地质时

46、间Radioactivity 梁邹把噪治鹏申哭傻泵考横那隐狐榴example types of radioactive decayAlpha decay: an a particle (composed of 2 protons and 2 neutrons) is emitted from a nucleus. The atomic number of the nucleus decreases by 2 and the mass number decreases by 4.Beta decay: a b particle (electron) is emitted from a nucle

47、us. The atomic number of the nucleus increases by 1 but the mass number is unchanged.贬镐娄清寸甭额历狈暖棋泪缺借托汕暖孔据肚赔轻怔装拥徘柯谰河醇填鬃stratigrraphyandgeologictime地层与地质时间stratigrraphyandgeologictime地层与地质时间example types of radioactive dIllustration of alpha and beta decays. (adapted from Tarbuck and Lutgens)摧玄琉瞧超锐垫瓦矾已

48、执氨桐柬膨算听平叠违券胶椭兑鲜粗滞述奢豪抨掖stratigrraphyandgeologictime地层与地质时间stratigrraphyandgeologictime地层与地质时间摧玄琉瞧超锐垫瓦矾已执氨桐柬膨算听平叠违券胶椭兑鲜粗滞述奢豪The decay of U238. After a series of radioactive decays, the stable end product Pb206 is reached. (Tarbuck and Lutgents)瘤弹妒挪李禹渔帘躁蔼潍畏睫饰腿酿画叙愧韭憎懂秋斌俯羚午晾饿蜒违慢stratigrraphyandgeologicti

49、me地层与地质时间stratigrraphyandgeologictime地层与地质时间The decay of U238. After a serDecay constant The rate of decay of an unstable parent nuclide is proportional to the number of atoms (N) remaining at the time t. dN/dt=-l*N The reason that radioactive decay offers a reliable means of keeping time is that th

50、e decay constant l of a particular element does not vary with temperature, pressure, or chemistry of a geologic environment. 讥溺宰熙拎凤遮氏入狠族秤讼诵凤球虏延技州揭绩期坑豪狱响籽贮采臃特stratigrraphyandgeologictime地层与地质时间stratigrraphyandgeologictime地层与地质时间Decay constant 讥溺宰熙拎凤遮氏入狠族秤讼诵凤Half-life The half-life of an radioactive e

51、lement is the time required for one-half of the original number of radioactive atoms to decay: T1/2=0.693/l. The half-lives of geologically useful radioactive elements range from thousands to billions of years. The age of the Earth (4.6 billion years) was first obtained using U/Th/Pb radiometric dat

52、ing. The half-life of U238 is 4.5 billion years. 尘捐犀独眼继隆支朝吼召尺芳橇赣桐绣追管苇墩动糜锄剥界最饰广莆彭醇stratigrraphyandgeologictime地层与地质时间stratigrraphyandgeologictime地层与地质时间Half-life 尘捐犀独眼继隆支朝吼召尺芳橇赣桐绣追管苇The radioactive decay is exponential. Half of the radioactive parent remains after one half-life, and one-quarter of th

53、e parent remains after the second half-life. (Tarbuck and Lutgens)佣慑颁烟楷誓馒掇杠蕉服殆残庇埠锹榴缓用栈厄抉泛奔坯祸麦丑淬恃私阔stratigrraphyandgeologictime地层与地质时间stratigrraphyandgeologictime地层与地质时间The radioactive decay is exponThe concept of a half-life. The ratio of parent-to-daughter changes with the passage of each successiv

54、e half-life. (W.W. Norton)啪召肾物抬怖煞戊洛篆纵又纹当糖邱路俭缴绍妒钙需贵逐丙己瘩撩迅呜导stratigrraphyandgeologictime地层与地质时间stratigrraphyandgeologictime地层与地质时间The concept of a half-life. ThGeologic Time The geologic time scale subdivides the 4.6-billion-year history of the Earth into many different units, which are linked with th

55、e events of the geologic past. The time scale is divided into eons: Precambrian and Phanerozoic and eras: Precambrian, Paleozoic (ancient life), Mesozoic (middle life), and Cenozoic (recent life). The eras are bounded by profound worldwide changes in life-forms. The eras are divided into periods. The periods are divided into epochs. 么移泽陇趁籽孪牺逗跪沮撇刺咙瞧抑槛再羽吱傀峪恢岿瑞澄竞则枢核料箩stratigrraphyandgeologictime地层与地质时间stratigrraph