Pliocene to Holocene geomorphic evolution and paleogeography of the El’gygytgyn Lake region, NE Russia
Pliocene to Holocene geomorphic evolution and paleogeography of the El’gygytgyn Lake region, NE Russia
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俄罗斯东北部埃尔吉吉金湖地区上新世至全新世地貌演化和古地理
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发表时间：
2006
期刊：
影响因子：
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通讯作者：
V. Smirnov
中科院分区：
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作者：
O. Glushkova;V. Smirnov
地貌，岩性和地层实地研究以及花粉数据和矿物学研究已被用来提出上新世和更新世古地理重建的El'gygytgyn陨石坑区。在上新世早期的丘陵剥蚀平原上，撞击的瞬间被记录为一个由撞击岩碎片组成的“混乱层位”。这个混乱的层位位于上新世晚期冲积沉积层之间。在上新世晚期的后半期，该地区处于构造活动期，当时阿纳迪尔低地被抬升，导致冲积沉积物堆积在火山口以南的盆地中。区域气候变冷是上新世晚期的特征，它支持了冻土带的扩展和多年冻土的形成。沿恩米瓦姆河沿着530 m等高线间隔的35-40 m高阶地形成于中更新世。这个阶地代表了湖泊的最高水位。由于另一波隆起，恩米瓦姆河上游的侵蚀和切割增加。此外，El'gygytgyn湖流量增加，导致湖平面开始下降中更新世。持续的降温导致了以草本植物为主的北极苔原的发展。中、晚更新世冰川没有到达埃尔吉格特金湖区。晚更新世在湖周围形成了高9-11 m的湖阶，晚更新世在湖周围形成了高2-3 m的湖阶。在过去的5000年里，随着现代海岸线的发展，湖泊水位持续下降。
Geomorphic, lithologhic, and stratigraphic field studies as well as pollen data and mineralogical study have been used to propose Pliocene and Pleistocene paleogeographic reconstructions of the El’gygytgyn meteorite crater area. The moment of impact is recorded above the early Pliocene hill denudation plain as a “chaotic horizon” consisting of fragments of impactite rocks. This chaotic horizon lies between layers of late Pliocene alluvial sediments. During the second half of the late Pliocene, the region was tectonically active, when the Anadyr lowland was uplifted causing alluvial sediments to accumulate in the basins to the south of the crater. Regional climatic cooling, which supported the spread of tundra and the formation of permafrost is characteristically to late Pliocene. The 35–40 m high terrace that roughly follows the 530 m contour interval along the Enmyvaam River formed during the middle Pleistocene. This terrace represents the maximum lake level. Erosion and incision of the upper Enmyvaam River increased due to another wave of uplift. Additionally, El’gygytgyn Lake discharge increased causing lake level to begin to drop in the Middle Pleistocene. Cooling continued, which led to the development of herb-dominated arctic tundra. middle and late Pleistocene glaciations did not reach the El’gygytgyn lake region. The 9–11 m high lacustrine terrace was formed around the lake during the late Pleistocene and the 2–3 m high lacustrine terrace formed later during the Holocene. During the last 5000 years, the lake level has continued to drop as the modern coastline developed.