Late Quaternary Niger Delta, and Adjacent Areas: Sedimentary Environments and Lithofacies
Late Quaternary Niger Delta, and Adjacent Areas: Sedimentary Environments and Lithofacies
复制标题
DOI：
10.1306/a663363a-16c0-11d7-8645000102c1865d
复制
发表时间：
1965-05
期刊：
影响因子：
3.5
通讯作者：
J. R. Allen
中科院分区：
文献类型：
--
作者：
J. R. Allen
几内亚湾晚第四纪尼日尔三角洲是一个大型的弧形“经典”三角洲，与边缘河口和障壁岛-泻湖复合体有关。晚第四纪三角洲透镜（最小体积为900立方千米）是尼日利亚沿海平原地槽内最新的增生物。沉积物起源于一个巨大的和地质复杂的腹地分散通过三角洲河流，潮汐，波浪和洋流。三角洲的生长开始于威斯康星州晚期的海平面低水位期，当时河流侵蚀大陆架，到达大陆架边缘海底峡谷上方的河口。晚第四纪三角洲堆积的最古老的地层单位是一个海滨平原砂（旧砂），代表海侵到内地。后来，在全新世，当海平面变得相对稳定，海退前进的砂同心排列的三角洲环境产生了年轻的套房，最上层的地层形成的三角洲透镜。该套岩相从开阔陆棚粘土向上渐变，通过前三角洲斜坡层状粘土、粉砂和砂，到三角洲前缘台地、河口坝和海滩上形成的层状砂。在三角洲可见部分边缘的海滩山脊屏障岛屿后面，存在潮汐红树林沼泽，其中沉积了富含有机物的砂和粉砂。在三角洲漫滩环境中，交叉分层的河坝砂与顶层粉砂和粘土一起堆积。晚第四纪尼日尔三角洲的沉积框架是基于基本上同心的相元素，在许多其他的“经典”三角洲，而不是放射状元素，如在密西西比鸟足三角洲。
The Late Quaternary Niger delta in the Gulf of Guinea is a large, arcuate "classical" delta associated with marginal estuary and barrier island-lagoon complexes. The Late Quaternary deltaic lens (minimum volume 900 cubic kilometers) is the latest accretion within the Nigerian Coastal Plain geosyncline. Sediment originating in a vast and geologically complex hinterland is dispersed through the delta by river, tidal, wave, and ocean currents. Delta growth began during the Late Wisconsin lowstand of the sea when the rivers entrenched the continental shelf to reach mouths above submarine canyons at the shelf edge. The oldest stratigraphical unit of the Late Quaternary deltaic pile is a strand plain sand (Older Sands) representing a marine transgression into the hinterland. Later, in the Holocene, when sea-level became relatively stable, regressive advance across the sands of concentrically arranged delta environments gave rise to the Younger Suite, the uppermost stratigraphical formation in the deltaic lens. Lithofacies of this suite grade upward from open shelf clays, through pro-delta slope layered clays, silts, and sands, to well-bedded sands formed on the delta-front platform, river mouth bars, and beaches. Behind beach idge barrier islands fringing the visible part of the delta occur tidal mangrove swamps in which organic-rich sands and silts are being deposited. Cross-stratified river bar sands are accumulating in association with top-stratum silts and clays in the delta floodplain environment. The sedimentary framework of the Late Quaternary Niger delta is based on essentially concentric facies elements, as in many other "classical" deltas, rather than on radial elements as in the Mississippi birdfoot delta.