Emergent Marine Record and Paleoclimate of the Last Interglaciation along the Northwest Alaskan Coast
Emergent Marine Record and Paleoclimate of the Last Interglaciation along the Northwest Alaskan Coast
复制标题
阿拉斯加西北海岸末次间冰期的新兴海洋记录和古气候
作者：
J. Brigham‐Grette;D. Hopkins
摘要阿拉斯加西部和北方海岸沿着有一次同位素亚阶段5e的Pelukian海侵，它记录了最后一次间冰期的高海平面。地层学表明，在最后一次间冰期循环中，海平面只有一次达到这个高度。从诺姆的模式产地到白令海的圣劳伦斯岛，再到博福特海的东部边界，佩卢基阶沉积物中含有一些生活在海外的动物群，表明当时的沿海沃茨比现在要温暖。这些沉积物中软体动物的氨基酸比例向北向巴罗方向降低，与现代区域温度梯度一致。诺姆岛和圣劳伦斯岛的化石组合表明，冬季海冰的界限是白令海峡以北，至少在现在位置以北800公里，白令海常年无冰。从钻孔中发现的Pelukian沉积物中的微型动物表明，大西洋水可能存在于浅博福特大陆架上，这表明北冰洋没有分层，北极海冰覆盖在一段时间内不是常年性的。在阿拉斯加西部的沿海地区，云杉林地向西延伸，超出了它们现在的分布范围;在阿拉斯加北方的北极沿海平原，云杉格罗夫斯林可能已经进入了科尔维尔河上游的盆地。阿拉斯加北极沿海平原古比克组的弗拉克斯曼成员是在海洋同位素亚阶段5a沉积的，记录了基瓦廷西北部第5阶段冰盖的破裂。
Abstract The last interglacial high sea-level stand, the Pelukian transgression of isotope substage 5e, is recorded along the western and northern coasts of Alaska by discontinuous but clearly traceable marine terraces and coastal landforms up to about 10 m altitude. The stratigraphy indicates that sea level reached this altitude only once during the last interglacial cycle. From the type area at Nome, to St. Lawrence Island in the Bering Sea, to the eastern limit of the Beaufort Sea, Pelukian deposits contain extralimital faunas indicating that coastal waters were warmer than present. Amino acid ratios in molluscs from these deposits decrease to the north toward Barrow, consistent with the modern regional temperature gradient. Fossil assemblages at Nome and St. Lawrence Island suggest that the winter sea-ice limit was north of Bering Strait, at least 800 km north of its present position, and the Bering Sea was perennially ice-free. Microfauna in Pelukian sediments recovered from boreholes indicate that Atlantic water may have been present on the shallow Beaufort Shelf, suggesting that the Arctic Ocean was not stratified and the Arctic sea-ice cover was not perennial for some period. In coastal regions of western Alaska, spruce woodlands extended westward beyond their modern range and in northern Alaska, on the Arctic Coastal Plain, spruce groves may have entered the upper Colville River basin. The Flaxman Member of the Gubik Formation on the Alaskan Arctic Coastal Plain was deposited during marine isotope substage 5a and records the breakup of an intra-stage 5 ice sheet over northwestern Keewatin.