Morphology and sedimentary processes on the continental slope off Pine Island Bay, Amundsen Sea, West Antarctica
Morphology and sedimentary processes on the continental slope off Pine Island Bay, Amundsen Sea, West Antarctica
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DOI：
10.1130/b25791.1
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发表时间：
2006-05
影响因子：
4.9
通讯作者：
J. Dowdeswell;J. Evans;C. Ó. Cofaigh;John B. Anderson
中科院分区：
文献类型：
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作者：
J. Dowdeswell;J. Evans;C. Ó. Cofaigh;John B. Anderson
利用条带水深测量、参数海底剖面仪(TOPAS)记录和沉积岩心研究了阿蒙森海东部松岛湾大陆边缘的地貌和沉积。一个主要的跨陆架槽延伸到114°W的大陆架边缘，在完全冰川条件下，快速流动的冰通过该海槽排干了西南极冰盖。槽口附近坡度为4°，东侧和西侧坡度较大。槽口以东和之外的等高线的凸起表明有一些斜坡进积。在其他地方，地震反射剖面显示了主要的陆架堆积和少量的斜坡堆积。松岛湾附近的斜坡上布满了沟渠和沟渠。在槽口前面，陆架边缘和最高斜坡上的沟渠直接与持续到大陆隆起的水道相连。其他沟渠间接地与进一步向下倾斜的渠道相连。TOPAS记录表明，沟渠系统充当了粗粒泥沙输送的管道。岩心由代表河道沉积的浊积岩和泥石流沉积的直径相组成。在隆起和深海平原上，砂质浊积岩与半深海泥浆互层。在冰川盛行期间，西南极冰盖延伸到陆架边缘，沿着线源将水饱和的冰层和浑浊的水直接输送到大陆斜坡。沟渠系统可能是沉积物重力流的产物，这些重力流来自于沿冰盖边缘释放饱和的水和浑浊的水，随后可能因全新世期间与海冰产生相关的密集冷水和咸水的下坡流动而扩大。沟渠系统使沉积物能够绕过大陆斜坡。阿蒙森海大陆坡沟渠系统形态的空间差异可能与沉积物重力流动过程以及从冰盖输送到陆架边缘的沉积物的速率和组成的不同有关。斜坡和深海平原上的岩心沉积物记录了广泛存在的浊积砂，表明冰川来源的沉积物已经发生了向下的转移。这支持了我们的解释，即海底航道源于大规模浪费，是大规模浪费的管道。上坡海底航道一直延伸到北至∼67°S的深海平原，由下坡浊流过程和沿坡底流相互作用产生的泥沙漂移和泥沙波分隔开来。类似的深海沉积过程在西南极洲的大部分地区和南极半岛的西侧也在进行。
Morphology and sedimentation on the Pine Island Bay continental margin, eastern Amundsen Sea, is investigated using swath bathymetry, parametric subbottom profiler (TOPAS) records, and sediment cores. A major cross-shelf trough extends to the continental shelf edge at 114°W, through which fast-flowing ice drained the West Antarctic Ice Sheet under full-glacial conditions. The slope adjacent to the trough mouth is 4°, whereas to the east and west it is steeper. A bulge in bathymetric contours beyond and east of the trough mouth indicates some slope progradation. Elsewhere, seismic-reflection profiles indicate major shelf aggradation and minor slope progradation. Networks of gullies and channels dominate the slope adjacent to Pine Island Bay. In front of the trough mouth, gullies at the shelf edge and uppermost slope connect directly with channels that continue to the continental rise. Other gullies connect indirectly with channels further downslope. TOPAS records indicate that gully-channel systems acted as conduits for coarse-grained sediment transfer. Cores comprise turbidites representing channel deposits and diamicton facies deposited by debris flows. Sandy turbidites interbedded with hemipelagic muds occur on the rise and abyssal plain. The West Antarctic Ice Sheet extended to the shelf edge during full glacials, delivering water-saturated till and turbid water directly to the continental slope along a line source. Gully-channel systems are probably a product of sediment gravity flows derived from the release of water-saturated till and turbid water along the ice-sheet margin, perhaps augmented subsequently by downslope flow of dense cold and saline water associated with sea-ice production during the Holocene. The gully-channel systems enable sediment to bypass the continental slope. Spatial variations in gully-channel system morphology along the Amundsen Sea continental slope are probably linked to differences in sediment gravity flow processes and the rate and composition of sediment delivered to the shelf edge from the ice sheet. Cored sediments on the slope and abyssal plain record the widespread presence of turbidite sands, indicating that downslope transfer of glacier-derived sediments has taken place. This supports our interpretation that submarine channels are derived from, and are conduits for, mass wasting. Submarine channels on the upper slope continue into the abyssal plain as far north as ∼67°S. They are separated by sediment drifts and sediment waves resulting from the interaction between downslope turbidity current processes and along-slope bottom currents. Similar deep-sea sedimentary processes operate along much of West Antarctica and the western side of the Antarctic Peninsula.