Bedrock platforms within the Ross Embayment, West Antarctica: Hypotheses for ice sheet history, wave erosion, Cenozoic extension, and thermal subsidence
Bedrock platforms within the Ross Embayment, West Antarctica: Hypotheses for ice sheet history, wave erosion, Cenozoic extension, and thermal subsidence
复制标题
西南极洲罗斯海湾内的基岩平台：冰盖历史、波浪侵蚀、新生代扩张和热沉降的假设
DOI：
10.1029/2006gc001294
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发表时间：
2006
期刊：
影响因子：
3.7
通讯作者：
B. Luyendyk
中科院分区：
文献类型：
--
作者：
Douglas S. Wilson;B. Luyendyk
透冰雷达（主要是机载的）和海洋地震勘测揭示了罗斯湾部分区域下方海平面以下约100 - 350米处的高原和阶地，包括西南极冰盖、罗斯冰架和罗斯海东部。这些表面覆盖数千平方公里，被西南极冰流占据的基岩槽谷分隔开来。显著的高原位于爱德华七世半岛、赛普尔穹顶和罗斯福岛之下。覆盖在这些埋藏高原上的海洋地震数据和重力数据支持这样一种解释，即它们是由对基底的侵蚀造成的。这些由侵蚀形成的表面平坦且在很长距离内深度相近，并且环绕着玛丽·伯德地埋藏的崎岖基岩地形，这支持了是海洋侵蚀而非冰川侵蚀的解释。其中一个高原残余上的海洋地震反射剖面显示它是一个角度不整合面，切入渐新世晚期缓倾的沉积物中，并覆盖着薄而平的沉积物，这意味着该高原形成于中新世早期或更晚。高原侵蚀的较年轻界限源自对其机制的解释：侵蚀必然早于与西南极冰盖增长相关的沿海永久冰盖形成的时间，可能在1000万年前之前，也可能在1400万年前之前。赛普尔海岸沿线深度约为350米的高原，在去除过去和现在冰荷载的模型中，并没有回弹到接近海平面和波基面的位置。如果罗斯湾岩石圈自始新世到渐新世的大规模伸展以来一直在冷却和下沉，那么这种差异就可以得到解释。我们的解释需要罗斯海的地壳下沉，这反过来又意味着该区域过去的基岩海拔更高。较高的地形为局部冰盖的积累提供了机会，并在新生代晚期之前导致了海平面波动。
Ice‐penetrating radar (mostly airborne) and marine seismic surveys have revealed plateaus and terraces about 100–350 m below sea level beneath parts of the Ross Embayment, including the West Antarctic ice sheet, the Ross Ice Shelf, and the eastern Ross Sea. These surfaces cover many thousands of square kilometers and are separated by bedrock troughs occupied by the West Antarctic ice streams. Prominent plateaus are under Edward VII Peninsula, Siple Dome, and Roosevelt Island. Marine seismic data and gravity data over the buried plateaus support an interpretation that they were caused by erosion into basement. The flat and level nature of the surfaces that were formed by erosion, are near the same depth over large distances, and fringe the buried rugged bedrock topography of Marie Byrd Land supports an interpretation of marine rather than glacial erosion. Marine seismic reflection profiles over one of the plateau remnants show it as an angular unconformity cut into gently dipping sediments of late Oligocene age, draped with thin, flat‐lying sediments, implying that the plateau is early Miocene or younger. The younger limit for plateau erosion follows from the interpretation of the mechanism: erosion must predate permanent ice along the coast associated with the growth of the West Antarctic ice sheet, probably prior to 10 Ma and possibly prior to 14 Ma. The plateaus along the Siple Coast, with depths around 350 meters, do not rebound to close to sea level and wave base for models of removing past and present ice load. This discrepancy can be explained if Ross Embayment lithosphere has been cooling and subsiding since significant extension in Eocene to Oligocene time. Our interpretation requires crustal subsidence in the Ross Sea, which in turn implies higher bedrock elevations in the past within this region. Higher‐standing topography presented an opportunity for the accumulation of local ice sheets and caused sea level fluctuation prior to late Cenozoic time.