Mellett Claire L, Hodgson David M, Plater Andrew J, Mauz Barbara, Selby Ian, Lang Andreas
School of Environmental Sciences, University of Liverpool, Liverpool, L69 7ZT, UK.
School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, UK.
Geomorphology (Amst). 2013 Dec 1;203(100):79-96. doi: 10.1016/j.geomorph.2013.03.030.
The erosional morphology preserved at the sea bed in the eastern English Channel dominantly records denudation of the continental shelf by fluvial processes over multiple glacial-interglacial sea-level cycles rather than by catastrophic flooding through the Straits of Dover during the mid-Quaternary. Here, through the integration of multibeam bathymetry and shallow sub-bottom 2D seismic reflection profiles calibrated with vibrocore records, the first stratigraphic model of erosion and deposition on the eastern English Channel continental shelf is presented. Published Optical Stimulated Luminescence (OSL) and C ages were used to chronometrically constrain the stratigraphy and allow correlation of the continental shelf record with major climatic/sea-level periods. Five major erosion surfaces overlain by discrete sediment packages have been identified. The continental shelf in the eastern English Channel preserves a record of processes operating from Marine Isotope Stage (MIS) 6 to MIS 1. Planar and channelised erosion surfaces were formed by fluvial incision during lowstands or relative sea-level fall. The depth and lateral extent of incision was partly conditioned by underlying geology (rock type and tectonic structure), climatic conditions and changes in water and sediment discharge coupled to ice sheet dynamics and the drainage configuration of major rivers in Northwest Europe. Evidence for major erosion during or prior to MIS 6 is preserved. Fluvial sediments of MIS 2 age were identified within the Northern Palaeovalley, providing insights into the scale of erosion by normal fluvial regimes. Seismic and sedimentary facies indicate that deposition predominantly occurred during transgression when accommodation was created in palaeovalleys to allow discrete sediment bodies to form. Sediment reworking over multiple sea-level cycles (Saalian-Eemian-early Weichselian) by fluvial, coastal and marine processes created a multi-lateral, multi-storey succession of palaeovalley-fills that are preserved as a strath terrace. The data presented here reveal a composite erosional and depositional record that has undergone a high degree of reworking over multiple sea-level cycles leading to the preferential preservation of sediments associated with the most recent glacial-interglacial period.
在英吉利海峡东部海床保存的侵蚀地貌主要记录了在多个冰期 - 间冰期海平面周期中，大陆架被河流作用剥蚀的过程，而非第四纪中期通过多佛海峡的灾难性洪水作用。在此，通过整合多波束测深和用振动取芯记录校准的浅地层二维地震反射剖面，给出了英吉利海峡东部大陆架侵蚀与沉积的首个地层模型。已发表的光释光（OSL）和碳年代数据被用于从时间上约束地层，并使大陆架记录能够与主要气候/海平面时期进行对比。已识别出五个主要侵蚀面，其之上覆盖着离散的沉积层序。英吉利海峡东部的大陆架保存了从海洋同位素阶段（MIS）6到MIS 1的过程记录。在低水位或相对海平面下降期间，河流下切形成了平面状和河道状侵蚀面。下切的深度和横向范围部分取决于下伏地质（岩石类型和构造结构）、气候条件以及与冰盖动态和西北欧主要河流排水格局相关的水和沉积物流量变化。保存了MIS 6期间或之前主要侵蚀的证据。在北部古河谷内识别出了MIS 2时期的河流沉积物，这为正常河流作用的侵蚀规模提供了见解。地震和沉积相表明，沉积主要发生在海侵期间，此时古河谷中形成了容纳空间，使得离散的沉积体得以形成。河流、海岸和海洋作用在多个海平面周期（萨勒冰期 - 埃姆间冰期 - 早魏克塞尔冰期）对沉积物进行的再塑造，形成了多层、多边的古河谷充填层序，这些层序作为阶地保存下来。此处呈现的数据揭示了一个复合的侵蚀与沉积记录，该记录在多个海平面周期中经历了高度的再塑造，导致与最近冰期 - 间冰期相关的沉积物得到优先保存。
