Anomalous Early Triassic sedimentation and weathering in western Guizhou

Deng Xusheng; Yu Wenchao

doi:10.16186/j.cnki.1673-9787.2024110001

Abstract：Objectives To reveal the early Triassic sedimentary and weathering characteristics and changes in the Weining area,Guizhou,conduct research on Early Triassic abnormal sedimentation and weathering in western Guizhou.Methods the thickness,petrography and geochemistry of the lower Triassic clastic rocks were analyzed,and were compared with those of the upper Permian in the study and adjacent areas.Results In the early Triassic Induan,a large amount of the detrital materials from the Emeishan basalt were deposited in Weining area,and the average sedimentation rate during this period was as high as 786 m/Myr,which showed the anomalous and rapid deposition.In addition,the early Triassic Induan sedimen-tation rate was 33 times that of the late Permian,indicating a significant change in sedimentation.The lower Triassic clastic rocks had slightly lower w(Y)/w(Ho)value than that of the source rocks,with low LOL/IOB values,CIA and MIA(o)values,which were obviously lower than that of the upper Permian clastic rocks in this area and its adjacent areas,showing weak chemical weathering.Conclusions Under the back-ground of hot climate and weak weathering in the early Triassic,the anomalous and high sedimentation rate should be related to the strong physical denudation and weathering in this period.This could be a sedimen-tary response to extreme geological events such as the mass extinction of terrestrial forest systems,the strengthening of hydrosphere cycles and widespread drought caused by the end-Permian mass extinction.