Evolution of deep-water climbing dunes in the Rockall Trough — Implications for overflow currents across the Wyville-Thomson Ridge in the (?)late Miocene
Evolution of deep-water climbing dunes in the Rockall Trough — Implications for overflow currents across the Wyville-Thomson Ridge in the (?)late Miocene
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DOI：
10.1016/0025-3227(87)90027-2
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发表时间：
1987
期刊：
影响因子：
2.9
通讯作者：
P. Richards;J. Ritchie;A. R. Thomson
中科院分区：
文献类型：
--
作者：
P. Richards;J. Ritchie;A. R. Thomson
A（？）在罗卡尔海槽北方部分的海底和海底以下，水深1080-1180 m，发现了一个面积为350 km 2的晚中新世沙丘。整个地区的地震反射记录揭示了沙丘内部底形排列的细节。沙丘可以分为三个部分，即基底沙丘、中间过渡阶段和上部正弦包。这三个细分是类似的小规模，沙波纹漂移系统的条件下，不断减少energy.The基础攀登沙丘向南迁移的证据，沿着罗卡尔槽轴观察到的阶段。它们可能主要是由牵引流沉积而成，这些牵引流是在中新世晚期从挪威海、威维尔-汤姆森海岭进入北大西洋的密集、寒冷的底层水溢流中形成的。由于威维尔-汤姆森海岭作为溢流屏障的影响越来越大，这种电流能量下降，沙丘系统的沉积风格发生了变化。电流强度的降低伴随着迁移率的降低和悬浮负荷沉积的增加，沙丘的几何形状发生相应的变化。当目前的强度进一步下降的山脊成为一个更永久的障碍，溢出，沙丘系统演变成一个正弦相位，沉积为主的沉降悬浮负载material.The沙丘系统是侵蚀覆盖在一个年轻的地方，未注明日期的存款，可能代表来自罗卡尔槽东侧的滑塌片。
A (?)late Miocene dune field covering an area of 350 km2has been identified at and below the sea bed in the northern part of the Rockall Trough, in 1080–1180 m of water. Seismic reflection records across the area reveal details of the internal bedform arrangement of the dunes. A three-fold subdivision of the dunes can be made, into basal climbing dunes, an intermediate transitional phase and an upper sinusoidal package. These three subdivisions are similar to the phases observed elsewhere in small-scale, sand-ripple drift systems evolving under conditions of decreasing energy.The basal climbing dunes show evidence of southwards migration, along the axis of the Rockall Trough. They were probably deposited primarily from traction currents formed in dense, cold, bottom water overflow moving from the Norwegian Sea, over the Wyville-Thomson Ridge and into the North Atlantic during the late Miocene. As this current energy decreased due to the increasing influence of the Wyville-Thomson Ridge as a barrier to overflow, the depositional style of the dune system changed. The decrease in current strength was accompanied by a decrease in migration rate and an increase in suspension load deposition, with a corresponding change in dune geometry. When the current strength decreased further as the ridge became a more permanent barrier to overflow, the dune system evolved into a sinusoidal phase, with deposition dominated by the fallout of suspension load material.The dune system is erosionally overlain in places by a younger, undated deposit that may represent a slump sheet derived from the eastern side of the Rockall Trough.