三角洲沉积体系 (2).ppt
《三角洲沉积体系 (2).ppt》由会员分享,可在线阅读,更多相关《三角洲沉积体系 (2).ppt(85页珍藏版)》请在三一文库上搜索。
1、第三章 三角洲沉积体系 DELTA SYSTEMS 第一节第一节 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特征及沉积模式 第三节第三节 古代三角洲沉积鉴别标志及其古代三角洲沉积鉴别标志及其 与油气资源的关系与油气资源的关系 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 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 1.三角
2、洲的亚环境和沉积特征 两套术语(two sets of terms for deltas) ) Based on gradient of delta profileBased on gradient of delta profile(吉尔伯特吉尔伯特,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 topsettopset or delta platform or delta platform n n 前积层或三角洲斜坡前积层或三角洲斜坡 foresetforeset or delta slope or delta slope n n 底积层或前三角洲底积层
3、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 delta plain delta plain 上部上部 高潮面以上高潮面以上 下部下部 低潮面以上低潮面以上 n n 三角洲前缘三角洲前缘 delta front delta front 浪基面以上浪基面以上 n n 前三角洲前三角洲 prodeltaprodelta 浪浪基面以下基面以下 水上三角洲
4、 水下三角洲 所有三角洲都可以分 为水上三角洲(三角 洲平原:又分上部和 下部)和水下三角洲 (三角洲前缘和前三 角洲) Physiographic and Sediment Characteristics of Alluvial Deltaic Systems Variations in sediment input, outflow velocity, wave and current energy, and other factors discussed cause the depositional features of deltas to exhibit a high degree
5、of variability from one delta to another. Nevertheless, all deltas can be divided into subaerial and subaqueous components, each of which can be further subdivided (Fig. 10.15). The subaqueous delta plain lies seaward of the lower deltaic plain below low-tide water level and is characterized by rela
6、tively 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 (DELTA PLAIN) The subaerial component of deltas is generally larger than the subaqueous component and is divided into an upper delta plain, wh
7、ich 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 commonly the oldest part of the delta and is dominated by fluvial processes. The lower delta plain is exposed during low tide but is covered b
8、y water during high tide. Thus, it is subjected to both fluvial and marine processes. (1)三角洲平原 (DELTA PLAIN) Upper Delta Plain Sediments The upper delta plain lies mainly above tidal influence and is little affected by marine processes, and thus similar to fluvial environments in many respects, exce
9、pt that areas of swamp, marsh and lake are usually widespread and that channels may bifurcate downstream; Sedimentation on the upper delta is dominated by distributary-channel migration and associated fluvial sedimentation processes such as channel and point-bar deposition, overbank flooding, and cr
10、evassing into lake basins. The principal depositional environments include braided channels(辫状河道), meandering channels(曲流河道), lacustrine delta fill, backswamps, and floodplain environments such as swamps, marshes, and freshwater lakes(淡水 湖泊) (Coleman and Prior, 1982). Therefore, upper delta-plain se
11、diments are predominantly fluvial sands, gravels, and muds that may be closely associated with lacustrine, swamp, and marsh deposits. 湿地 n定义:指海洋和内陆常年有浅层积水或土壤过湿 的地段。 n表达湿地的词约有30个左右,但学术上有个比较 统一的名词沼泽. n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,如swamp, marsh, bog, moor, fen 等.某些文献中指出其间有些差别,例如swamp 指木本植物多于marsh而排水情况优于
12、bog的一 种湿地; marsh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; marsh土常多碱 性,而bog常多酸性; moor常指较开阔、地势较 高、排水较差、有小灌木丛以致泥炭的湿地; fen则是英国常用的名词等. (1)三角洲平原 (DELTA PLAIN) Lower Delta Plain Sediments Affected by both fluvial and Affected by both fluvial and basinalbasinal processes processes. . The width of the lower delta plain
13、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, and may be flanked by marginal-basin or bay-fill deposits. Distributary channels are numerous, but environments between channels make up
14、 the largest percentage of the lower delta plain. These environments include actively migrating tidal channels, natural levees, interdistributary bays(分流间湾), bay fills (crevasse splays), marshes, and swamps (Coleman and Prior, 1982). Sediments:The major sand bodies generated in this environment are
15、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 climates, evaporites (蒸发盐) also may be deposited in some parts of the lower delta plain. Deposits of the lower delta plain also co
16、mmonly include abandoned distributary deposits. These consist of locally derived sands, muds, and organic debris that gradually fill distributary channels after they have been abandoned by the main stream owing to blocking or other processes that cause channel shifting. (1)三角洲平原 (DELTA PLAIN) 两个主要单元
17、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(DistributaryDistributary 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 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(Inter-Inter-distributarydistributary area area) 天然天然堤堤
18、-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 。 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 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。 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 ,由细沙和粉沙组成。常见粒序层、沙纹层和平
19、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 镜状层理。含海相动物化石。镜状层理。含海相动物化石。 (2)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
20、, 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 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
21、of the subaqueous delta, the delta front, may be dominated by high-energy marine processes, including waves, longshore currents, and tides in some cases. The deposits typically consist in part of sands, and possibly gravels, deposited near the river mouths, forming distributary-mouth-bar deposits. I
22、n a general way, these deposits grade seaward to finer sands and coarse silts that settle from suspension to form the distal bar. On wave- and tide- dominated deltas, sediment is reworked and winnowed by these processes, creating well-sorted delta-front sheet sands that are cross-bedded on a variety
23、 of scales. (2)三角洲前缘 (DELTA FRONT) 水下分流河道沉积水下分流河道沉积-是陆上分流河道的延伸部分。沉是陆上分流河道的延伸部分。沉 积物中常含粘土碎块,具交错层理、流水沙纹层理和积物中常含粘土碎块,具交错层理、流水沙纹层理和 侵蚀面等,可见向上变细的序列。侵蚀面等,可见向上变细的序列。 水下天然堤沉积水下天然堤沉积-由极细沙和粉沙组成。可见沙纹层由极细沙和粉沙组成。可见沙纹层 理、浪成波痕、虫孔和包卷纹层等。理、浪成波痕、虫孔和包卷纹层等。 河口沙坝沉积河口沙坝沉积-由沙质沉积物组成。质地纯净,分选由沙质沉积物组成。质地纯净,分选 良好,具多方向槽状交错层和冲刷面
24、。河口坝末端通良好,具多方向槽状交错层和冲刷面。河口坝末端通 常称为末端坝,为细沙、粉沙和泥组成的交互层。具常称为末端坝,为细沙、粉沙和泥组成的交互层。具 反粒序,有水平纹层、波状及透镜状层理,河口坝单反粒序,有水平纹层、波状及透镜状层理,河口坝单 元形成向上变粗的序列。元形成向上变粗的序列。 前缘席状沙前缘席状沙-河口坝经海洋营力改造形成。成层性好河口坝经海洋营力改造形成。成层性好 ,沙纹层理发育。,沙纹层理发育。 (3)前三角洲 (PRODELTA) The remaining seaward part of the subaqueous delta is called the prode
- 配套讲稿:
如PPT文件的首页显示word图标,表示该PPT已包含配套word讲稿。双击word图标可打开word文档。
- 特殊限制:
部分文档作品中含有的国旗、国徽等图片,仅作为作品整体效果示例展示,禁止商用。设计者仅对作品中独创性部分享有著作权。
- 关 键 词:
- 三角洲沉积体系 2 三角洲 沉积 体系
链接地址:https://www.31doc.com/p-2982373.html