Erosion at extended continental margins: Insights from new aerogeophysical data in eastern Dronning Maud Land
Erosion at extended continental margins: Insights from new aerogeophysical data in eastern Dronning Maud Land
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扩展大陆边缘的侵蚀：来自德龙宁莫德地东部新航空地球物理数据的见解
DOI：
10.1016/j.gr.2018.05.011
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发表时间：
2018
影响因子：
6.1
通讯作者：
Läufer
中科院分区：
文献类型：
--
作者：
Eagles;Karlsson;Ruppel;Steinhage;Läufer
对扩展大陆边地形演变机制的建模、岩石冷却、沉积和沉积解释差异很大。从南极洲德龙宁毛德地边缘的观测结果到目前为止还没有对这些解释做出有力的贡献。在这里，我们提出了新的航空重力和雷达数据描述东部的边缘。内陆的一个高（2.5公里）的大悬崖，高原顶部的一个分支网络的山谷表明保存的河流景观与SW导向排水下的冷基冰盖。谷底的斜坡表明，这一景观是修改在阿尔卑斯式冰川期开始之前，目前的冷为基础的阶段约34马。里瑟-拉森海近海盆地中的沉积物量与估计已被侵蚀的岩石量相平衡，这些岩石是通过陡崖和大陆架断裂之间的北向排水而搬运的。这些盆地的地层学表明，大部分的侵蚀发生在晚侏罗世大陆解体后的约4000万年。这种侵蚀是不太可能已占主导地位的背磨损，因为所需的速率的悬崖撤退到目前的位置是快于景观演变的数值模型建议是可能的。我们认为，一个额外的组成部分的侵蚀，向下磨损向海的一个预先存在的内陆排水分水岭。大悬崖和内陆高原的东部终端位于西拉格希尔德海槽，这是一个长300公里，宽15-20公里，深1.6公里的冰下山谷，容纳着西拉格希尔德冰川。许多过度加深（超过300米）的谷底段证明了它的经验，重大的冰川侵蚀。厚的晚侏罗世和早白垩世沉积物从海槽口成扇形延伸到东部的里瑟-拉森海，揭示了更早的河谷历史。在东南极洲内陆的这条河的集水区缺乏晚侏罗世的浮雕形成过程表明，这种侵蚀与区域气候变化有关。
Modelling-, rock cooling-, sedimentation- and exposure-based interpretations of the mechanisms by which topography evolves at extended continental margins vary widely. Observations from the margin of Dronning Maud Land, Antarctica, have until now not strongly contributed to these interpretations. Here, we present new airborne gravity and radar data describing the eastern part of this margin. Inland of a tall (2.5 km) great escarpment, a plateau topped by a branching network of valleys suggests preservation of a fluvial landscape with SW-directed drainage beneath a cold-based ice sheet. The valley floor slopes show that this landscape was modified during a period of alpine-style glaciation prior to the onset of the current cold-based phase around 34 Ma. The volume of sediments in basins offshore in the Riiser-Larsen Sea balances with the volume of rock estimated to have been eroded and transported by north-directed drainage from between the escarpment and the continental shelf break. The stratigraphy of these basins shows that most of the erosion occurred during the ~40 Myr following late Jurassic continental breakup. This erosion is unlikely to have been dominated by backwearing because the required rate of escarpment retreat to its present location is faster than numerical models of landscape evolution suggest to be possible. We suggest an additional component of erosion by downwearing seawards of a pre-existing inland drainage divide. The eastern termination of the great escarpment and inland plateau is at the West Ragnhild trough, a 300 km long, 15–20 km wide and up to 1.6 km deep subglacial valley hosting the West Ragnhild glacier. Numerous overdeepened (by >300 m) segments of the valley floor testify to its experience of significant glacial erosion. Thick late Jurassic and early Cretaceous sediments fanning out from the trough's mouth into the eastern Riiser-Larsen Sea betray an earlier history as a river valley. The lack of late Jurassic relief-forming processes in this river's catchment in the interior of East Antarctica suggests this erosion was related to regional climatic change.
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