柴达木盆地西南区始新世-中新世事件地层研究

EOCENE-MIOCENE EVENT STRATIGRAPHY OF SOUTHWESTERN QAIDAM BASIN

在阐述区域地质基础上,开展了研究区始新世—中新世事件地层学的研究,并建立了其事件地层系统,识别出5种事件面、8种事件带、6种事件组合和1个事件集群。事件面有隆升事件面、岩相转换事件面、洪泛事件面、生物灭绝事件面、气候转换(波动)事件面;根据地质事件的纵向发育特征,建立了暖热事件带、温凉事件带、δ18O高值事件带、δ18O低值事件带、挤压断陷事件带、走滑断陷事件带、湖盆扩张事件带和湖盆收缩事件带等,其中,暖热事件与δ18O低值事件、温凉事件与δ18O高值事件、地壳隆升与不整合事件、气候波动与生物灭绝事件均具有成因联系,它们分别构成了一个事件组合;所有事件组合构成了该时期的事件集群。上述事件带中,挤压断陷事件带、走滑断陷与湖盆扩张事件带以及湖泊收缩事件带体现了柴达木盆地西部的演化过程,而且这个演化过程与青藏高原的隆升密不可分。由于印度大陆与欧亚大陆的碰撞、拼合与俯冲挤压,促使青藏高原不断隆升和一系列喜山运动(共四幕)的产生,同时导致了研究区始新世—中新世事件集群的发生。

Based on regional geological and stratigraphic analysis, an event stratigraphic framework of Eo- cene-Miocene in the Qaidam Basin has been established. Five types of event stratigraphic surface, eight e- vent stratigraphic zones, six event stratigraphic associations, and one event stratigraphic assemblage have been recognized. Among them, event stratigraphic surfaces include the uplifting surface, lithofacies trans- formation surface, flooding surface, species extinction surface and climate change （fluctuation） surface. According to the spatial and temporal patterns of geological events, eight event stratigraphic zones have been established, including the warm climate zone, cool climate zone, high ~180 zone, low ~1~O zone, fold- ing and faulting zone, strike-slip fault depression zone, lake basin expansion zone and lake basin contrac- tion zone. Among these event stratigraphic zones, warm event climate zone and low ~180 zone, cool cli- mate zone and high 8180 zone, crustal uplift and unconformity, climatic fluctuation and species extinction event, are genetically related. Therefore, they constituted event stratigraphic association. These event stratigraphic associations make the Eocene-Miocene event stratigraphic assemblage. The folding and faul- ting event, strike slip fault depression, lake basin expansion event, and lake basin contraction event in western Qaidam Basin are controlled by the Tibetan plateau uplift. Because of continental collision between India and Eurasian, Tibetan plateau uplift and a series of Himalayan movement resulted in the development of the Eocene-Miocene event stratigraphic assemblage in western Qaidam Basin.