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Late Pleistocene shelf‐edge delta clinoforms along the rift margin of the northern Okinawa Trough
Geological Journal ( IF 1.8 ) Pub Date : 2020-03-26 , DOI: 10.1002/gj.3811
Ang Li 1, 2 , Feng Cai 1, 2 , Nengyou Wu 1, 2 , Qing Li 1, 2 , Guijing Yan 1, 2 , Yunbao Sun 1, 2 , Gang Dong 1, 2 , Di Luo 1, 2
Affiliation  

Sedimentological study into the architecture of continental margins reveals its importance in predicting the partition of sediment budget between the shelf and the deep‐water settings. The sediment delivery towards the deep‐water basin during sea‐level lowstands can be hindered along rift margins. Here we use a 2D seismic survey from the northern Okinawa Trough to identify a set of clinoform seismic units elongating along the western slope, where the rifting activity occurred later than the late Pleistocene. The clinoform units are interpreted as a shelf‐margin delta complex based on the following observations: (a) the sediments clearly prograde across the eroded paleo‐shelf on the dip‐oriented sections; (b) there is some negative relief along two extensively traceable reflections, indicating the probable existence of paleo‐channels working as the potential pathways of sediment delivery for the shelf‐margin deposits; and (c) an eroded surface is easily recognized in the seismic data, possibly marking the sea‐level lowstand during which the shelf‐margin delta formed. The oxygen isotopes of the core QZ01 are taken as a proxy for the variation of the relative sea level and indicate its fast fluctuation in the past 180 kyr. We interpret how the shelf‐margin delta evolved during the late Pleistocene and propose that the subsidence and the rift faulting lead to the starvation of sediments near the shelf edge. As a result, there could be more sediments depositing along the active rift margin, while few of them would be transported to the deep‐water basin and re‐deposit as turbidites.

中文翻译:

冲绳海槽北部裂谷边缘的晚更新世陆缘三角斜型

对大陆边缘结构的沉积学研究表明,它对于预测架子和深水环境之间的沉积物预算分配很重要。在海平面低潮期,沉积物向深水盆地的输送可能会沿裂谷边缘受到阻碍。在这里,我们使用了来自冲绳海槽北部的2D地震勘测,以识别沿西坡延伸的一系列斜形地震单元,其中裂谷活动比晚更新世晚。根据以下观察结果,斜面单元被解释为陆架-三角洲复合体:(a)沉积物在倾斜方向剖面上的侵蚀古架上明显地前进;(b)沿两个可广泛追踪的反射有一些消极的缓解,表明可能存在古河道,作为架子边缘沉积物的沉积物输送的潜在途径;(c)在地震数据中很容易识别出被侵蚀的表面,可能标志着形成了陆架三角洲的海平面低位。核心QZ01的氧同位素被用来代表相对海平面的变化,并指示其在过去180年中的快速波动。我们解释了在更新世晚期陆架边缘三角洲如何演化,并提出了沉降和裂谷断层导致了陆架边缘附近沉积物的饥饿。结果,沿活动裂谷边缘可能会有更多的沉积物沉积,而很少有沉积物会被输送到深水盆地并以浊石的形式重新沉积。
更新日期:2020-03-26
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