三角洲沉积体系.ppt
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1、第三章 三角洲沉积体系DELTA SYSTEMS第一节 三角洲的环境特点及其沉积作用第二节 三角洲的沉积特征及沉积模式第三节 古代三角洲沉积鉴别标志及其 与油气资源的关系第二节 三角洲的沉积特征及沉积模式一、曲流河三角洲沉积体系一、曲流河三角洲沉积体系 二、辫状河三角洲沉积二、辫状河三角洲沉积体系体系三、扇三角洲沉积体系三、扇三角洲沉积体系一、曲流河三角洲沉积一、曲流河三角洲沉积三角洲的亚环境和沉积特征三角洲的亚环境和沉积特征三角洲的主要类型、沉积相组合、三角洲的主要类型、沉积相组合、沉积旋回及演化沉积旋回及演化1.1.三角洲的亚环境和沉积特征三角洲的亚环境和沉积特征两套两套术语术语(two
2、sets of terms for deltas)Based on gradient of delta profileBased on gradient of delta profile(吉尔伯特吉尔伯特吉尔伯特吉尔伯特,美国,美国,美国,美国,18851885):n n顶积层或三角洲台地顶积层或三角洲台地顶积层或三角洲台地顶积层或三角洲台地 topsettopset or delta platform or delta platformn n前积层或三角洲斜坡前积层或三角洲斜坡前积层或三角洲斜坡前积层或三角洲斜坡 foresetforeset or delta slope or delta
3、slopen n底积层或前三角洲底积层或前三角洲底积层或前三角洲底积层或前三角洲 bottomsetbottomset or prodelta or prodelta推荐使用的术语推荐使用的术语Based on delta-building processes:Based on delta-building processes:n n三角洲平原三角洲平原三角洲平原三角洲平原 delta plain delta plain 上部上部上部上部 高潮面以上高潮面以上高潮面以上高潮面以上 下部下部下部下部 低潮面以上低潮面以上低潮面以上低潮面以上n n三角洲前缘三角洲前缘三角洲前缘三角洲前缘 delt
4、a front delta front 浪基面以上浪基面以上浪基面以上浪基面以上n n前三角洲前三角洲前三角洲前三角洲 prodeltaprodelta 浪浪浪浪基面以下基面以下基面以下基面以下水上三角洲水上三角洲水下三角洲水下三角洲所有三角洲都可以分所有三角洲都可以分为水上三角洲(三角为水上三角洲(三角洲平原:又分上部和洲平原:又分上部和下部)和水下三角洲下部)和水下三角洲(三角洲前缘和前三(三角洲前缘和前三角洲)角洲)Physiographic and Sediment Characteristics of Alluvial Deltaic Systems Variations in se
5、diment input,outflow velocity,wave and current energy,and other factors discussed cause the depositional features of deltas to exhibit a high degree of variability from one delta to another.Nevertheless,all deltas can be divided into subaerial and subaqueous components,each of which can be further s
6、ubdivided(Fig.10.15).The subaqueous delta plain lies seaward of the lower deltaic plain below low-tide water level and is characterized by relatively open marine faunas.The uppermost part of the subaqueous delta,lying at water depths down to 10 m or so,is commonly called the delta front.(1)三角洲平原)三角洲
7、平原 (DELTA PLAIN)The subaerial component of deltas is generally larger than the subaqueous component and is divided into an upper delta plain,which lies largely above high-tide level,and a lower delta plain,lying between low-tide mark and the upper limit of tidal influence.The upper delta plain is co
8、mmonly the oldest part of the delta and is dominated by fluvial processes.The lower delta plain is exposed during low tide but is covered by water during high tide.Thus,it is subjected to both fluvial and marine processes.(1)三角洲平原)三角洲平原 (DELTA PLAIN)Upper Delta Plain SedimentsThe upper delta plain l
9、ies mainly above tidal influence and is little affected by marine processes,and thus similar to fluvial environments in many respects,except that areas of swamp,marsh and lake are usually widespread and that channels may bifurcate downstream;Sedimentation on the upper delta is dominated by distribut
10、ary-channel migration and associated fluvial sedimentation processes such as channel and point-bar deposition,overbank flooding,and crevassing into lake basins.The principal depositional environments include braided channels(辫状河道辫状河道),meandering channels(曲流河道曲流河道),lacustrine delta fill,backswamps,an
11、d floodplain environments such as swamps,marshes,and freshwater lakes(淡水淡水湖泊湖泊)(Coleman and Prior,1982).Therefore,upper delta-plain sediments are predominantly fluvial sands,gravels,and muds that may be closely associated with lacustrine,swamp,and marsh deposits.湿地湿地n n定义定义定义定义:指海洋和内陆常年有浅层积水或土壤过指海洋和
12、内陆常年有浅层积水或土壤过指海洋和内陆常年有浅层积水或土壤过指海洋和内陆常年有浅层积水或土壤过湿的地段。湿的地段。湿的地段。湿的地段。n n表达湿地的词约有表达湿地的词约有表达湿地的词约有表达湿地的词约有3030个左右个左右个左右个左右,但学术上有个比但学术上有个比但学术上有个比但学术上有个比较统一的名词较统一的名词较统一的名词较统一的名词沼泽沼泽沼泽沼泽.n n在湿地研究影响最大的英语国家中比较普遍的在湿地研究影响最大的英语国家中比较普遍的在湿地研究影响最大的英语国家中比较普遍的在湿地研究影响最大的英语国家中比较普遍的名词有四五个名词有四五个名词有四五个名词有四五个,如如如如swamp,ma
13、rsh,bog,moor,fenswamp,marsh,bog,moor,fen等等等等.某些文献中指出其间有些差别某些文献中指出其间有些差别某些文献中指出其间有些差别某些文献中指出其间有些差别,例如例如例如例如swampswamp指木本植物多于指木本植物多于指木本植物多于指木本植物多于marshmarsh而排水情况优于而排水情况优于而排水情况优于而排水情况优于bogbog的一的一的一的一种湿地种湿地种湿地种湿地;marshmarsh指软、湿、低的草本覆被为主指软、湿、低的草本覆被为主指软、湿、低的草本覆被为主指软、湿、低的草本覆被为主的有由水过渡到陆的趋势的湿地的有由水过渡到陆的趋势的湿地的
14、有由水过渡到陆的趋势的湿地的有由水过渡到陆的趋势的湿地;marsh;marsh土常土常土常土常多碱性多碱性多碱性多碱性,而而而而bogbog常多酸性常多酸性常多酸性常多酸性;moor;moor常指较开阔、地常指较开阔、地常指较开阔、地常指较开阔、地势较高、排水较差、有小灌木丛以致泥炭的湿势较高、排水较差、有小灌木丛以致泥炭的湿势较高、排水较差、有小灌木丛以致泥炭的湿势较高、排水较差、有小灌木丛以致泥炭的湿地地地地;fen;fen则是英国常用的名词等则是英国常用的名词等则是英国常用的名词等则是英国常用的名词等.(1)三角洲平原)三角洲平原 (DELTA PLAIN)Lower Delta Pla
15、in SedimentsAffected by both fluvial and Affected by both fluvial and basinalbasinal processes processes.The width of the lower delta plain is greatest on deltas where tidal range is large.This plain includes the active distributary system of the delta,as well as abandoned distributary-fill deposits
16、,and may be flanked by marginal-basin or bay-fill deposits.Distributary channels are numerous,but environments between channels make up the largest percentage of the lower delta plain.These environments include actively migrating tidal channels,natural levees,interdistributary bays(分流间湾分流间湾),bay fil
17、ls(crevasse splays),marshes,and swamps(Coleman and Prior,1982).Sediments:The major sand bodies generated in this environment are bay-fill deposits,which may form thin sand wedges stacked one on top of the other and separated by finer-grained,interdistributary-bay and marsh deposits.In very arid clim
18、ates,evaporites(蒸发盐蒸发盐)also may be deposited in some parts of the lower delta plain.Deposits of the lower delta plain also commonly include abandoned distributary deposits.These consist of locally derived sands,muds,and organic debris that gradually fill distributary channels after they have been ab
19、andoned by the main stream owing to blocking or other processes that cause channel shifting.(1)三角洲平原)三角洲平原 (DELTA PLAIN)两个主要单元两个主要单元两个主要单元两个主要单元 (Two principal components of Delta plain Two principal components of Delta plain):n n分流河道沉积分流河道沉积分流河道沉积分流河道沉积(DistributaryDistributaryDistributaryDistribut
20、ary channels channels channels channels)为沙和粉沙沉积物。横剖面形态为近于对称的透镜体。为向上变为沙和粉沙沉积物。横剖面形态为近于对称的透镜体。为向上变为沙和粉沙沉积物。横剖面形态为近于对称的透镜体。为向上变为沙和粉沙沉积物。横剖面形态为近于对称的透镜体。为向上变细的沉积序列。细的沉积序列。细的沉积序列。细的沉积序列。n n分流河道间沉积分流河道间沉积分流河道间沉积分流河道间沉积(Inter-Inter-Inter-Inter-distributarydistributarydistributarydistributary area area area
21、area)天然天然天然天然堤堤堤堤-发育在河道两侧,由细沙、粉沙和泥质组成。沙质发育在河道两侧,由细沙、粉沙和泥质组成。沙质发育在河道两侧,由细沙、粉沙和泥质组成。沙质发育在河道两侧,由细沙、粉沙和泥质组成。沙质沉积内部具沙纹交错层和流水波痕沉积内部具沙纹交错层和流水波痕沉积内部具沙纹交错层和流水波痕沉积内部具沙纹交错层和流水波痕。沼泽及湖泊沼泽及湖泊沼泽及湖泊沼泽及湖泊-排水不良,但植物繁茂,沉积物主要为富含有排水不良,但植物繁茂,沉积物主要为富含有排水不良,但植物繁茂,沉积物主要为富含有排水不良,但植物繁茂,沉积物主要为富含有机质的暗色泥岩夹泥炭和煤层。植物化石丰富,根土构造发机质的暗色泥
22、岩夹泥炭和煤层。植物化石丰富,根土构造发机质的暗色泥岩夹泥炭和煤层。植物化石丰富,根土构造发机质的暗色泥岩夹泥炭和煤层。植物化石丰富,根土构造发育。湖泊的规模通常较小,沉积物主要为泥岩。育。湖泊的规模通常较小,沉积物主要为泥岩。育。湖泊的规模通常较小,沉积物主要为泥岩。育。湖泊的规模通常较小,沉积物主要为泥岩。决口扇沉积决口扇沉积决口扇沉积决口扇沉积-发育在天然堤两侧和分流间海湾,呈扇状分布,发育在天然堤两侧和分流间海湾,呈扇状分布,发育在天然堤两侧和分流间海湾,呈扇状分布,发育在天然堤两侧和分流间海湾,呈扇状分布,由细沙和粉沙组成。常见粒序层、沙纹层和平行层理。由细沙和粉沙组成。常见粒序层、
23、沙纹层和平行层理。由细沙和粉沙组成。常见粒序层、沙纹层和平行层理。由细沙和粉沙组成。常见粒序层、沙纹层和平行层理。分流间湾沉积分流间湾沉积分流间湾沉积分流间湾沉积-分流间湾是指分流河道间与海洋相通的相对分流间湾是指分流河道间与海洋相通的相对分流间湾是指分流河道间与海洋相通的相对分流间湾是指分流河道间与海洋相通的相对低凹的地区。为泥质,含少量粉沙和细沙,具水平层理和透低凹的地区。为泥质,含少量粉沙和细沙,具水平层理和透低凹的地区。为泥质,含少量粉沙和细沙,具水平层理和透低凹的地区。为泥质,含少量粉沙和细沙,具水平层理和透镜状层理。含海相动物化石。镜状层理。含海相动物化石。镜状层理。含海相动物化石
24、。镜状层理。含海相动物化石。(2)三角洲前缘三角洲前缘(DELTA FRONT)The subaqueous delta plain constitutes that area of a delta that lies seaward of low tide level and above wave base,and actively receives fluvial sediments.It may extend outward for distances of a few kilometers to tens of kilometers to water depths as much as
25、 300 m.Deposits of the subaqueous delta thus form the base over which subaerial delta deposits prograde as the delta builds seaward.The uppermost part of the subaqueous delta,the delta front,may be dominated by high-energy marine processes,including waves,longshore currents,and tides in some cases.T
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