Soft sediment deformation structures in the Lixian lacustrine sediments, eastern Tibetan Plateau and implications for postglacial seismic activity

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• 作者：Hanchao Jiang ; ^{hcjiang@ies.ac.cn" class="auth_mail" title="E-mail the corresponding author} ; Ning Zhong ; Yanhao Li ; Hongyan Xu ; Huili Yang ; Xiaoping Peng
• 关键词：Lacustrine sequence ; Soft-sediment deformation (SSD) ; Postglacial period ; OSL dating ; Lixian ; Eastern margin of the Tibetan Plateau
• 刊名：Sedimentary Geology
• 出版年：2016
• 出版时间：October 2016
• 年：2016
• 卷：344
• 期：Complete
• 页码：123-134
• 全文大小：5173 K

文摘

The eastern margin of the Tibetan Plateau is characterized by frequent earthquakes, which are closely associated with tectonic activity. To assess tectonic activity during the Late Pleistocene, we studied a well-exposed, 23-m-thick lacustrine sequence on the eastern margin of the plateau and found a variety of soft-sediment deformation (SSD) structures. Distributed in 24 stratigraphic levels, they comprise clastic dykes, ball-and-pillow structures, flame structures, clastic gravels, micro-faults, and slump folds. Most of the SSD structures indicate deformation mechanisms related to liquefaction and/or fluidization processes, most probably triggered by paleoseismic events. Given at least 4 historical earthquakes of M > 7 in the study area, most SSD structures in the Lixian lacustrine sequence indicate seismic events with M > 6 while simple flame structures point to some lower-magnitude earthquakes. OSL dating indicates that the sequence accumulated between 15.8 and 6.0 ka, giving a mean recurrence interval of 480 years for the 24 events, and demonstrating that lacustrine sediments in eastern Tibet have the potential to record a continuous seismic history on the centennial scale.