Structure, distribution, and evolution history of the Early Holocene erosional mud ridge system on the inner East China Sea shelf near the Yangtze River estuary
Structure, distribution, and evolution history of the Early Holocene erosional mud ridge system on the inner East China Sea shelf near the Yangtze River estuary
复制标题
DOI：
10.1016/j.geomorph.2017.01.011
复制
发表时间：
2017-04
期刊：
影响因子：
3.9
通讯作者：
Zhibing Feng;Baohua Liu;Yuexia Zhao;Li Xishuang;O. Dada;Li Jiang;Shaokun Si
中科院分区：
文献类型：
--
作者：
Zhibing Feng;Baohua Liu;Yuexia Zhao;Li Xishuang;O. Dada;Li Jiang;Shaokun Si
利用所收集的高分辨率地震数据集和随附的钻孔和测深数据，我们系统地评估了形态，建筑，沉积学，并在中国东海（ECS）大陆架内部的侵蚀泥脊的演变。我们发现了20个泥脊，地震反射剖面穿越出露或埋藏的泥脊，宽3.0-30.1 km，高2.5-17.3 m。泥脊主要由灰色粘土质淤泥组成，在地震剖面上包含平行至亚平行反射体。它们形成于约10-12 ka BP的河口环境中。研究区东部部分泥脊具有冲刷特征。考虑泥脊的相对位置，连同地形特征，使我们能够映射四个线性泥脊（LMR）。东南-北西向的大磁共振长度> 50 km，宽度为3.0-9.5 km，相互平行。它们还显示不对称的形状，与陡峭的斜坡SW。一些LMR的东段暴露在本海底，而其他部分主要覆盖的中，晚全新世地层。由于LMR与现代潮汐沙脊在形状和方向上有相似之处，我们假设它们是在均匀潮流下形成的。地震数据突出显示，沙脊的内部反射层由倾斜的斜坡组成，与LMR有很大不同，这一特征主要是由于ECS陆架内部和中外部沉积物粒度组成的差异。东加勒比海中部至外部大陆架被粗粒沉积物覆盖（即，在多旋回潮流的作用下，这些沉积物在靠近侵蚀区的位置被改造和沉积，从而形成多相沙脊。然而，细粒沉积物（即，覆于东海陆架内侧的粉质粘土和粘性粉土被潮流带离侵蚀区，形成残留泥脊。证据表明，LMR是在8-10 ka BP期间，早全新世地层受到持续的东南向流冲刷而形成的。LMR的演化经历了3个阶段：（a）~ 10-12 ka BP海侵地层的形成;（B）~ 8-10 ka BP强烈的海槽侵蚀; 8 kaBP后局部侵蚀轻微，保存完好。
Utilizing the collected high-resolution seismic dataset and accompanying borehole and bathymetric data, we systematically evaluated the morphology, architecture, sedimentology, and evolution of erosional mud ridges within the inner East China Sea (ECS) shelf. We identified 20 mud ridges, i.e., seismic reflection profile crossings of exposed or buried mud ridges, which are 3.0–30.1 km in width and 2.5–17.3 m in height. The mud ridges are composed predominantly of gray clayey silt, and on seismic profiles contain parallel to subparallel reflectors. They formed around ~ 10–12 ka BP within an estuarine environment. Scouring features of some mud ridges on the eastern part of the study area can be recognized. Consideration of the relative positions of mud ridges, together with the topographical features, enables us to map four linear mud ridges (LMRs). The SE-NW oriented LMRs are > 50 km in length, 3.0–9.5 km in width and running parallel to each other. They also display asymmetric shapes, with steeper slopes to the SW. The eastern segments of some LMRs are exposed on the present seafloor whereas other segments are mainly overlain by the mid- and late Holocene strata. Since the LMRs share similarities with the modern tidal sand ridges in shape and orientation, we hypothesize that they are formed under a uniform tidal current. Seismic data highlight that the internal reflectors of sand ridges consist of dipping clinoforms and are significantly different from LMRs, a feature which is largely due to the difference in grain-size composition of sediments between the inner and mid-outer ECS shelf. The mid- to outer ECS shelf is capped by coarser-grained sediments (i.e., medium to fine-grained), which were reworked and deposited at locations near the erosional areas under a polycyclic tidal current, thus forming multiphase sand ridges. However, fine-grained sediments (i.e., silty clay and clayey silt) overlain on the inner ECS shelf with light mass were carried far away from the erosional areas by the tidal currents, and the relict mud ridges were built. Evidence shows that the LMRs were formed by the early Holocene strata being scoured by a persistent southeasterly flowing current during ~ 8–10 ka BP. The evolution of the LMRs occurred in three stages: (a) formation of the transgressional strata at ~ 10–12 ka BP, (b) strong trough erosion at ~ 8–10 ka BP, and (c) local adjustment (i.e., local erosion slightly and preservation) after ~ 8 ka BP.