沉积学报2025，Vol.43Issue(2)：439-452,14.DOI:10.14027/j.issn.1000-0550.2023.058
滇西保山地区石炭纪—二叠纪古海洋氧化还原环境
Paleooceanographic Redox Environment from the Carboniferous to Permian in the Baoshan area,Western Yunnan
摘要
Abstract
[Objective]Long-term and extensive glaciation occurred during the Late Carboniferous-Early Permian.In this period,the Baoshan Block,as a part of the Gondwana continental margin,experienced several transgres-sive-regressive cycles,preserving important information on the expansion or depletion of glaciers.This study focused on the Xiyi section,Dongshanpo section,and Woniusi section in the Baoshan area of western Yunnan,exploring the paleo-ocean redox environment from the Middle Carboniferous-Early Permian and analyzing the mechanism of anoxic events and the relationship with glaciation.[Methods]Pyrite framboid was widely utilized to reconstruct paleo-ocean redox conditions,given its different formation mechanisms in oxic and euxinic environments.The specific methods employed include statistical analysis of the size data of pyrite framboids through box-whisker plots,scatter plots of mean-standard deviation,and scatter plots of mean-skewness.[Results]The results indicate four distinct episodes of redox conditions:Interval Ⅰ,the late Tournaisian redox conditions varied rapidly from euxinic-anoxic to dysoxic-oxic.Interval Ⅱ,the Visean redox conditions changed from euxinic-anoxic to dysoxic-oxic.Interval Ⅲ,the middle Sakmarian to early Artinskian redox conditions were mainly oxic and dysoxic but punctuated by short anoxic-dysoxic episodes.Interval Ⅳ,the early Kungurian to the middle Roadian experienced the same trace as Interval Ⅲ.In gener-al,the redox environment of the paleo-ocean in the Baoshan area showed a trend of euxinic → anoxic → dysoxic →oxic.The Early Carboniferous was dominated by an anoxic-dysoxic environment,but the Early-Middle Permian was dominated by dysoxic-oxic environment.[Conclusions]Euxinic-anoxic events from the late Tournaisian to the early Visean are positively correlated with the positive drift of δ13Ccarb and the decrease of biomass.The other pieces of evi-dence also indicated an anoxic environment during the Early Carboniferous,and the euxinic-anoxic event of the Early Carboniferous in the Baoshan Block was likely a response to the prelude of the Late Paleozoic ice age.The redox con-dition of the Early and Middle Permian was more oxidizable than the Early Carboniferous,which may be related to the sea level falls caused by glacial events and the temperature fall resulting from the paleogeographic evolution of the Cimmerian region.Furthermore,this change may have played a key role in promoting the biotic recovery of the Early Permian in the study area.关键词
石炭纪/二叠纪/晚古生代大冰期/基默里地区/氧化还原条件/草莓状黄铁矿Key words
Carboniferous/Permian/Late Paleozoic Ice Age/Cimmerian region/redox conditions/pyrite framboid分类
地质学引用本文复制引用
王虎,赖俭康,常晓琳..滇西保山地区石炭纪—二叠纪古海洋氧化还原环境[J].沉积学报,2025,43(2):439-452,14.基金项目
国家自然科学基金项目(42272023)[National Natural Science Foundation of China,No.42272023] （42272023）
