DENG X S，YU W C. Anomalous Early Triassic sedimentation and weathering in western Guizhou[J]. Journal of Henan Polytechnic University( Natural Science), doi:10.16186/j.cnki.1673-9787.2024110001.

Received：2024-11-01

Revised：2024-12-04

Online：2024-12-05

Anomalous Early Triassic sedimentation and weathering in western Guizhou (Online)

DENG Xusheng ¹, YU Wenchao ²

（1. Guizhou Geological Survey，Guiyang 550081，China；2. School of Earth Sciences, China University of Geosciences(Wuhan) ，Wuhan 430074，China）

Abstract: The Permian-Triassic (252 million years ago) mass extinction constitutes the greatest biocrisis experienced by life in the Phanerozoic, during which climate and environment underwent remarkable changes. In this period, the Emeishan large igneous province experienced extensive post-eruption erosion resulting in the accumulation of voluminous volcanic detritus in the adjacent Youjiang Basin. These detrital sediments are of great significance for understanding the relationship between continental surface weathering, sourc-to-sink system and paleoclimate evolution in the southwestern margin of the South China Block during this period. Objectives To reveal the early Triassic sedimentary and weathering characteristics and changes in the Weining area, Guizhou, Methods we analyzed the thickness, petrography and geochemistry of the lower Triassic clastic rocks, and 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 is as high as 786 m/Myr, which shows the anomalous and rapid deposition. In addition, the early Triassic Induan sedimentation rate is 33 times that of the late Permian, indicating a significant change in sedimentation. The lower Triassic clastic rocks have slightly lower Y/Ho value than that of the source rocks, with low LOL/IOB values, CIA and MIA_(o) value, which is obviously lower than that of the upper Permian clastic rocks in this area and its adjacent areas, showing weak chemical weathering. Conclusions Under the background 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 sedimentary 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.

Key words：Guizhou; early Triassic; weathering; sedimentation; clastic rocks

CLC: P539.6