End-Triassic storm deposits in the lacustrine Sichuan Basin and their driving mechanisms  

作　　者：Jianli ZENG Tingshan ZHANG Mihai Emilian POPA Yongdong WANG Xi ZHANG Liqin LI Yuanyuan XU Ning LU Xiaoqing ZHANG 

机构地区：[1]School of Geoscience and Technology,Southwest Petroleum University Chengdu 610500,China [2]Sichuan Key Laboratory of Natural Gas Geology Southwest Petroleum University,Chengdu 610500,China [3]Faculty of Geology and Geophysics,Doctoral Schoolof Geology Laboratory of Palaeontology University of Bucharest.Bucharest 010041,Romania [4]Nanjing Institute of Geology and Palaeontology Chinese Academy of Sciences,Nanjing 210008,China [5]University of Chinese Academy of Sciences,Nanjing,Nanjing 210008,China [6]University of Chinese Academy of Sciences,Beijing 100049,China

出　　处：《Science China Earth Sciences》2024年第7期2383-2400,共18页中国科学（地球科学英文版）

基　　金：co-sponsored by the National Natural Science Foundation of China(Grant Nos.41972120,42172129);the State Key Laboratory of Palaeobiology and Stratigraphy(Grant No.173131)。

摘　　要：Storm deposits or tempestites are event sequences formed by storms,requiring at least a water temperature of 26.5℃.While inland lakes are unlikely to form storm deposits because of their limited width and water temperature.The Upper Triassic Xujiahe Formation in the Sichuan Basin is a set of coal-bearing,clastic sequences with dominant sedimentary facies varying from braided river delta to lacustrine settings,with storm deposits widely reported.In the Zilanba of Guanyuan area,in situ tree trunks on a palaeosol surface in Member Vof the Xujiahe Formation provide new evidence of a storm event.Six fallen-down directions of nine in situ tree trunks were predominant in the NW direction,contrary to the palaeocurrent direction of the underlying strata,suggesting that the southeasterlies prevailed during the end-Triassic in the northern Sichuan Basin.Massive mud clasts were frequently recorded in sandstones of the Xujiahe Formation,as well as in the Xindianzi section.These mud clasts showed a rip-up or a plastic deformation with upside-down V-shapes,were capped on an erosional surface,showed no transport traces and were therefore interpreted as a storm lag deposit.The megamonsoonal climate prevailed during the Late Triassic,although the megamonsoons themselves could not generate a storm deposition in the Xujiahe Formation due to its low maximum surface wind speed.The driving mechanism for generating storm deposits in the Xujiahe Formation is suggested to be tropical cyclones over the Tethys Ocean moving eastward,further landfalling on the western margin of the Sichuan Basin.Statistics of storm events in the circum-Tethys region show a widespread storm surge in low latitudes during the end-Triassic.The storm deposits at the top of the Xujiahe Formation represent a sedimentary response to the end-Triassic hyperthermal event.

关 键 词：Sichuan Basin End-Triassic Xujiahe Formation Storm deposits 

分 类 号：P534.51[天文地球—古生物学与地层学] P512.2[天文地球—地质学] P532