邓旭升，余文超. 贵州西部地区早三叠世异常沉积和风化作用[J].河南理工大学学报(自然科学版), doi:10.16186/j.cnki.1673-9787.2024110001.

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.

贵州西部地区早三叠世异常沉积和风化作用(网络首发)

邓旭升 ¹，余文超 ²

（1.贵州省地质调查院，贵州 贵阳 550081；2.中国地质大学（武汉）地球科学学院，湖北 武汉 430074）

摘要:二叠纪-三叠纪之交发生了显生宙最大的一次生物灭绝事件，其伴随着环境和气候的剧烈变化，因而一直是国内外研究热点。在该时期内，峨眉山大火成岩省在喷发后遭受了强烈的风化剥蚀，为右江盆地及其周缘提供了大量的碎屑沉积物质。这些碎屑沉积物对认识该时期华南板块西南地区的陆表风化作用、源-汇系统与古气候演变之间关系具有重要意义。 目的 为了揭示贵州威宁地区早三叠世沉积和风化作用的特征及其变化， 方法 本文对威宁地区下三叠统碎屑岩开展了厚度统计、岩相学和全岩地球化学分析，并与研究区及邻区上二叠统进行对比分析。 结果 威宁地区早三叠世印度期（251.902～251.2 Ma）沉积了大量来源于峨眉山玄武岩风化剥蚀的碎屑物质，该时期的平均沉积速率高达786 m/Myr，表现为异常而快速的沉积输入特征。此外，早三叠世印度期沉积速率是晚二叠世的33倍，指示了沉积作用的明显变化。该地区下三叠统碎屑岩的Y/Ho值略低于源岩，具有低IOL/IOB值、CIA值和MIA（o）值，明显低于该地区及其邻区上二叠统的碎屑岩，表现为微弱的化学风化作用。 结论 在早三叠世炎热气候和弱化学风化作用背景下，异常高的沉积速率应与该时期异常强烈的物理剥蚀及风化作用有关。这可能是对二叠纪末生物大灭绝导致的陆地森林系统大量消亡、水圈循环的强化和大范围干旱等极端地质事件的沉积响应。

关键词: 贵州；早三叠世；风化作用；沉积作用；碎屑岩

中图分类号：P539.6　　

doi: 10.16186/j.cnki.1673-9787.2024110001

基金项目: 贵州省地质矿产勘查开发局地质科研项目（黔地矿科合［2020］31号）；国家重点研发计划项目（2022YFF0800200）

收稿日期：2024-11-01

修回日期：2024-12-04

网络首发日期：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