华南地质2026，Vol.42Issue(1)：96-115,20.DOI:10.3969/j.issn.2097-0013.2026.01.005
湘西北慈利地区二叠-三叠纪之交沉积与氧化还原状态演化
Sedimentary and Palaeoredox Evolution During the Permian-Triassic Transition in Cili County,Northwestern Hunan Province
摘要
Abstract
The Cili section in northwestern Hunan is situated within the Xiakou-Lichuan Gulf along the northern margin of the middle Yangtze carbonate platform.During the Permian-Triassic transition,it represented a deep-water land shelf depositional environment in front of the platform,providing new evidence for revealing the evolution of marine ecosystems under different environment in this period.Based on an analysis of sedimentary microfacies and fossil assemblages,combined with pyrite framboid size data,this study reconstructs the paleo-depositional environment and redox condition evolution of the Cili section from late Permian to early Triassic.The results indicate that the section successively developed the Wujiaping formation,Dalong formation,and Daye formation from late Permian to early Triassic.The Wujiaping formation is dominated by foreslope deposits,containing brachiopod,echinoderm,and foraminifer assemblages.The Dalong formation was deposited in a restricted deep-water shelf setting with weak hydrodynamics,characterized by spherical radiolarians and siliceous sponge spicules.A significant biotic extinction event occurred at its top,accompanied by a shift to an inner deep-water shelf environment.The Daye formation mainly consists of mudstone and argillaceous limestone,interpreted as having been deposited in an outer deep-water shelf setting where fossils are rare,with only occasional bivalves observed.Pyrite framboid sizes reveal that oxygen-poor conditions began to develop at the top of the Wujiaping Formation and intensified gradually,reaching anoxic to euxinic states at the extinction boundary.Overall,sea level in the study area underwent a"rise-fall-rise"cycle across the Permian-Triassic transition,with oxygen levels decreasing during sea-level fall.In summary,the deep-water shelf facies in the Cili area during the Permian-Triassic mass extinction event was jointly controlled by sea-level fluctuations and marine redox conditions.关键词
二叠-三叠纪/生物大灭绝/沉积相/氧化还原/湘西北/华南Key words
Permian-Triassic/mass extinction/sedimentation/palaeoredox/Northwestern Hunan province/South China分类
天文与地球科学引用本文复制引用
黄亚飞,陈灿,罗琳,易智星,张保民..湘西北慈利地区二叠-三叠纪之交沉积与氧化还原状态演化[J].华南地质,2026,42(1):96-115,20.基金项目
中国地质调查局南方复杂构造区页岩油气成藏理论与工程技术创新中心开放基金(SOG-202411)、战略性矿产资源调查评价项目(2024ZRYJDC017)、国家自然科学基金(42230205)、中国地质调查局地质调查项目(DD20240047) （SOG-202411）
