Structural and tectonic evolution of the Ross Sea rift in the Cape Colbeck region, Eastern Ross Sea, Antarctica
Structural and tectonic evolution of the Ross Sea rift in the Cape Colbeck region, Eastern Ross Sea, Antarctica
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南极洲东罗斯海科尔贝克角地区罗斯海裂谷的构造和构造演化
DOI：
10.1029/2000tc001260
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发表时间：
2001
期刊：
影响因子：
4.2
通讯作者：
C. Siddoway
中科院分区：
文献类型：
--
作者：
B. Luyendyk;C. Sorlien;Douglas S. Wilson;L. Bartek;C. Siddoway
南极洲罗斯海的远东大陆架迄今为止相对未被勘探。该地区和西部玛丽伯德地位于罗斯海裂谷的东部边界，是西南极裂谷系的一部分，是世界上较大的伸展地壳区域之一。在研究船破冰船Nathaniel B的第9601次巡航期间，利用海洋地球物理学对科尔贝克角以西的罗斯海大陆架和玛丽伯德地西部的爱德华七世半岛进行了调查。帕尔默其目的是确定罗斯海裂谷东部边界的构造框架和构造历史，并将其与已知的西部玛丽伯德地相结合。绘制的区域的特点是被动边缘与平坦的过度加深的陆架切割的北走向科尔贝克槽，侵蚀特征形成于中新世和后来的冰川下切，遵循现有的基底结构的位置。在罗斯海识别的地震层序和不整合面与科尔贝克陆架区进行了对比。该剖面主要由渐新世晚期和更年轻的未变形的冰海层序组成，它们不整合地覆盖在早白垩世晚期至晚白垩世晚期和少量的早第三纪（？）断层层序这个不整合面被确定为RSU 6，在罗斯海东部的其他地方绘制。在RSU 6以下发现了两个单元，每个单元被一个不整合面隔开，在此称为RSU 7。这些层序充填了断裂基底中的北向半地堑，并被解释为同裂谷单元。RSU 7不整合面与玛丽伯德地西部陆上绘制的南极西部侵蚀面相关。大陆架上缺乏厚的早第三纪沉积物，表明存在重要的垂直构造。这一陆上和海上地区在早白垩世晚期和晚白垩世时期广泛断裂，高出海平面，并因长期侵蚀而倾斜，而在晚白垩世和新生代时期稳定沉降。沉降主要是由于岩石圈冷却后，在新生代的冰川和沉积物加载放大。早白垩世晚期冷却年龄的糜棱岩是从科尔贝克海槽的东南壁挖掘出来的。这一发现和我们在罗斯海东部绘制的正断层，我们将其归因于早白垩世晚期的拆离式伸展。该伸展方向与现今陆缘边缘的走向近平行，发生在玛丽伯德地的坎贝尔高原于179Ma裂陷之前。玛丽伯德地西部陆上的冷却事件表明，主要的延伸开始于105Ma。这也是古冈瓦纳大陆边缘沿着其他地区从俯冲向伸展的过渡时期。晚新生代期间，大陆架轻微向西倾斜是大陆架沿着持续沉降的结果，同时可能伴随着与东部玛丽伯德地穹隆相关的西部玛丽伯德地的隆起。罗斯海裂谷西部的早第三纪伸展在裂谷东侧没有强烈的反映。这里的事件与罗斯海裂谷西侧更知名的构造历史之间更强有力的相关性，有待于对我们在科尔贝克大陆架上绘制的单元进行采样和测年。
The far eastern continental shelf of the Ross Sea, Antarctica, has been relatively unexplored up to now. This region and western Marie Byrd Land are at the eastern limit of the Ross Sea rift, part of the West Antarctic rift system, one of the larger regions of extended crust in the world. The Ross Sea continental shelf west of Cape Colbeck and the Edward VII Peninsula in western Marie Byrd Land was investigated using marine geophysics during cruise 9601 of the research vessel ice breaker Nathaniel B. Palmer. The purpose was to determine the structural framework and tectonic history of the eastern border of the Ross Sea rift and to integrate this with what is known about western Marie Byrd Land. The region mapped is characterized by a passive margin with a flat overdeepened shelf cut by the north trending Colbeck Trough, an erosional feature formed in Miocene and later time by glacial downcutting that followed the locations of existing basement structures. Seismic sequences and unconformities identified in the Ross Sea were correlated into the Colbeck shelf area. The section comprises mostly undeformed glacial marine sequences of late Oligocene and younger age that are unconformably overlying late Early to Late Cretaceous and minor early Tertiary (?) faulted sequences. This unconformity is identified as RSU6, mapped elsewhere in the eastern Ross Sea. Two units are found below RSU6, each separated by an unconformity that is here named RSU7. These sequences fill north trending half grabens in the faulted basement and are interpreted as syn rift units. Unconformity RSU7 is correlated to the West Antarctic Erosion Surface mapped onshore in western Marie Byrd Land. The lack of thick early Tertiary sediments on the shelf suggests significant vertical tectonics. This onshore and offshore region was widely faulted in late Early and Late Cretaceous time, was high above sea level and was beveled by prolonged erosion, while subsiding steadily in Late Cretaceous and Cenozoic time. Subsidence was largely due to lithosphere cooling amplified later by glacial and sediment loading in Cenozoic time. Mylonites that have late Early Cretaceous cooling ages were dredged from the southeast wall of the Colbeck Trough. This finding and normal faults that we mapped in the eastern Ross Sea we attribute to detachment‐style extension in late Early Cretaceous time. This extension was directed subparallel to the trend of the present margin edge and occurred prior to the rifting of Campbell Plateau from Marie Byrd Land at ∼79 Ma. Cooling events onshore western Marie Byrd Land suggest the main extension began at ∼105 Ma. This is also the time of transition from subduction to extension elsewhere along the ancient Gondwana margin. Minor west tilting of the shelf during the late Cenozoic was the result of continued subsidence of the continental shelf along with possible uplift of western Marie Byrd Land associated with the Marie Byrd Land dome to the east. Early Tertiary extension in the western Ross Sea rift is not strongly reflected in the east side of the rift. A more robust correlation of the events here with the better known tectonic history on the west side of the Ross Sea rift awaits sampling and dating of the units we mapped on the Colbeck shelf.