Thermal History of Cambrian Burgess Shale-Type Deposits:New Insights from the Early Cambrian Chengjiang and Qingjiang Fossils of South China  

作　　者：Yuheng Qiao Linhao Cui Guangyuan Xing Dongjing Fu Chao Chang Robert Gaines Xingliang Zhang 

机构地区：[1]State Key Laboratory of Continental Dynamics,Shaanxi Key laboratory of Early Life and Environments,Department of Geology,Northwest University,Xi’an,710069,China [2]Department of Geology,Pomona College,Claremont,CA,91711,USA

出　　处：《Journal of Earth Science》2024年第4期1215-1223,共9页地球科学学刊（英文版）

基　　金：supported by the Natural Science Foundation of China(Nos.41930319,41621003,and EAR-1554897);the 111 Project(No.D17013);the Natural Science Basic Research Plan of Shaanxi Province(No.2022JC-DW5-01).

摘　　要：Burgess Shale-type deposits provide a wealth of information on the early evolution of animals.Questions that are central to understanding the exceptional preservation of these biotas and the paleoenvironments they inhabited may be obscured by the post-depositional alteration due to metamorphism at depth and weathering near the Earth’s surface.Among over 50 Cambrian BST biotas,the Chengjiang and Qingjiang deposits are well known for their richness of soft-bodied taxa,fidelity of preservation,and Early Cambrian Age.While alteration via weathering has been well-investigated,the thermal maturity of the units bearing the two biotas has not yet been elucidated.Here we investigate peak metamorphic temperatures of the two deposits using two independent methods.Paleogeotemperature gradient analyses demonstrate that the most fossiliferous sections of the Chengjiang were buried at a maximum depth of∼8500 m in the Early Triassic,corresponding to∼300°C,while the type area of the Qingjiang biota was buried at a maximum depth of∼8700 m in the Early Jurassic,corresponding to∼240°C.Raman geothermometer analyses of fossil carbonaceous material demonstrate that peak temperatures varied across localities with different burial depth.The two productive sections of the Chengjiang biota were thermally altered at a peak temperature of approximately 300°C,and the main locality of the Qingjiang biota experienced a peak temperature of 238±22°C.These results from two independent methods are concordant.Among BST deposits for which thermal maturity has been documented,the Qingjiang biota is the least thermally mature,and therefore holds promise for enriching our understanding of BST deposits.

关 键 词：the Chengjiang Biota the Qingjiang Biota burial history Raman geothermometer thermal history Burgess Shale-type Lagerstätte 

分 类 号：Q911.2[天文地球—古生物学与地层学] P534.41[生物学—古生物学] P612