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在瓜德鲁普统末期发生了一次大规模生物灭绝事件,多类生物均遭受重创.关于此次生物灭绝事件成因,有学者认为海洋缺氧是主要的直接原因之一,但瓜德鲁普统—乐平统(G-L)过渡时期海洋的氧化还原条件的研究开展得较少,缺少直接证据证明海洋缺氧和瓜德鲁普统末期生物灭绝的关系.草莓状黄铁矿粒径是指示沉积水体氧化还原条件的少数可靠的指标之一.由于微晶粒径大小与草莓状黄铁矿粒径大小密切相关,草莓微晶粒径大小同样也可以作为沉积水体的氧化还原指标.本文通过研究蓬莱滩剖面卡匹敦阶茅口组和吴家坪阶合山组下部草莓状黄铁矿微晶粒径特征,从而分析沉积环境的氧化还原状态.研究结果表明蓬莱滩剖面茅口组和合山组微晶粒径多数分布在0.4～ 1.2 μm之间,大部分样品微晶粒径分布相对较窄,部分样品分布较宽.茅口组—合山组界线处间歇性出现微晶粒径很小且分布范围窄的样品,其平均微晶粒径一般小于0.7 μm,最大值一般不超过1.2 μm,很可能指示硫化一缺氧的环境.茅口组和合山组大部分样品平均微晶粒径分布在0.7～ 1.0 μm之间,最大值一般不超过3.3 μm,很可能指示的是氧化—贫氧环境.蓬莱滩剖面硫化至缺氧环境对应着瓜德鲁普末期生物灭绝事件层位,说明这两者很可能存在因果关系.海洋的硫化缺氧很可能是瓜德鲁普末期生物灭绝的主要原因之一.“,”A mass extinction took place at the end of Guadalupian,seriously killing many species.For the causes of this extinction event,some researcher suggested that the marine anoxia was one of the major causes.However,there are few studies on this redox condition during the G-L transition period,lacking of direct evidence to support the relationship between ocean anoxia and mass extinction at the end of Guadalupian.Framboidal pyrite size distribution is one of the few reliable indicators of redox conditions of sedimentation water column.Since the microcrystal size is related with framboid pyrite size,its size distribution should be also a indicator of redox condition.In this paper,we study the microcrystal size distribution across the Maokou-Heshan Formations boundary in the Penglaitan section,so as to analyze the redox conditions of water column.The studied results show that the most microcrystallite size of Maokou and Heshan Formations range from 0.4 μm to 1.2 μm and has a narrow size variation,though some of the samples show a wider variation.At the Maokou Formation-Heshan Formation boundaries,the samples with a small size (average less than 0.7 μm) and a small the maximutn size (average less than 1.2 μm) intermittently occurs,likely indicating euxinic to anoxic environment.The average size of most samples from Maokou and Heshan Formations ranges from 0.7 μm to 1.0 μm with a maximum value less than 3.3 μm,probably indicating the dysoxic to oxic environment.In the Penglaitan section,the euxinic to anoxic layers is coincided with the mass extinction level at the G-L boundary,indicating a causal link between.Marine anoxia is probability one of the main causes of the end Guadalupian mass extinction.