广西蓬莱滩GSSP剖面G-L界线黄铁矿形态特征及其氧化还原意义

发布时间：2018-03-25 00:08

  本文选题：蓬莱滩GSSP剖面　切入点：G-L界线　出处：《东华理工大学》2017年硕士论文

【摘要】：瓜德鲁普末期发生了一次大规模的生物灭绝事件。关于该次生物灭绝的原因,前人给出了包括海洋缺氧,峨眉山玄武岩喷发、全球性海平面下降以及卡穆拉变冷事件等不同的解释。其中海洋缺氧被认为是生物灭绝的致死原因,关于G-L界线海水的氧化还原条件已有研究者做了部分研究工作,但多数研究剖面G-L界线生物记录不够完整,氧化还原条件的变化还需不同的氧化还原指标来进行讨论。本文对广西来宾蓬莱滩GSSP剖面瓜德鲁普统茅口组至乐平统合山组地层进行系统的野外勘察,详细分析卡匹敦期至吴家坪早期的生境型变化、黄铁矿形态以及草莓状黄铁矿粒径和微晶粒径特征。根据生境型变化和黄铁矿形态特征分别讨论卡匹敦期至吴家坪早期的海平面变化和氧化还原条件,从而探讨海平面变化和海洋缺氧对生物灭绝的影响。并综合分析广西来宾蓬莱滩GSSP剖面、湖北恩施田凤坪剖面和四川广元肖家坝剖面的草莓状黄铁矿微晶粒径特征,根据草莓状黄铁矿微晶粒径对氧化还原条件进行厘定。在蓬莱滩GSSP剖面上共识别出4个大类5个亚类生境型,包括Ⅱ2型、Ⅲ1型、Ⅲ2型、Ⅳ型、和Ⅴ型。生境型反映了在瓜德鲁普末期全球处于海退阶段,而乐平早期则变为海侵阶段。海平面较低水平对应着该时期主要的生物灭绝,造成海洋底栖类动物的死亡。但浮游、游泳类动物的灭绝高峰出现在海平面上升时期。说明瓜德鲁普末期海平面下降至少不是该时期生物灭绝的唯一原因。茅口组下部不含草莓状黄铁矿,黄铁矿以自形晶为主;中部的草莓状黄铁矿粒径平均值为5.86~10.20μm,大部分样品粒径最大值大于20μm,并且在Jinogondolella xuanhanensis牙形刺带顶部出现粒径小,变化范围窄的样品;上部缺少草莓状黄铁矿,以自形晶黄铁矿和过大生长的草莓状黄铁矿为主;茅口组顶部至合山组富含粒径较小的草莓状黄铁矿,大部分样品粒径最大值小于18μm,间歇性出现一些粒径小,变化范围窄的样品。这表明茅口早期(Jinogondolella shannoni牙形刺带)沉积水体为氧化的环境;中期(Jinogondolella altuaensis-Jinogondolella xuanhanensis牙形刺带)为长期贫氧环境,并在Jinogondolella xuanhanensis牙形刺带结束时期出现短期缺氧;茅口晚期为氧化至贫氧环境;茅口末期至吴家坪早期为缺氧环境中间歇性出现硫化或氧化-贫氧环境。出现缺氧层位与出现生物灭绝事件的层位相对应。硫化海水的上涌可以引起浅海底栖生物出现死亡,海洋缺氧很可能是导致瓜德鲁普末期生物灭绝的主要原因。在硫化环境中形成的草莓状黄铁矿微晶粒径平均值一般小于0.68μm,标准偏差一般小于0.3μm;而氧化至贫氧环境中形成的草莓状黄铁矿微晶粒径平均值一般大于0.86μm,标准偏差一般大于0.5μm。所以草莓状黄铁矿微晶粒径也可以用以指示氧化还原条件,在其标准偏差与平均值的交汇图中可以划分出硫化-缺氧环境、氧化-贫氧环境区域,以及两者之间的过渡带。
[Abstract]:There was a mass extinction event at the end of Gua de Rupp. About the cause of extinction of the previous time, are given including marine hypoxia, Mount Emei basaltic eruptions, global sea-level drop and Camurra cooling event of different interpretations. The marine hypoxia is a cause of death of extinction, the existing research on the boundary conditions of oxidation of G-L the water reducer to do some research work, but most of the research section of the G-L boundary biological records is not complete, change the redox conditions of different redox indicators need to be discussed. Carries on the system to the guests Guangxi Penglai beach profile GSSP Gua de Rupp series of Maokou Formation in the Heshan Le Ping all the detailed field investigation, Ping analysis of Kapidun Wu period to early habitat type change, pyrite framboid pyrite morphology and particle size and particle size characteristics of root. According to the change of habitat type and pyrite morphological characteristics were discussed Kapidun period to the early Wu Ping sea-level change and redox conditions, so as to explore the influence of sea level change and ocean anoxia on extinction. And a comprehensive analysis of Guangxi Laibin Penglai beach GSSP section, Hubei section and Sichuan Enshi Tian Fengping Guangyuan Xiao Xiangjiaba section framboid pyrite microcrystalline according to the characteristics of grain size, framboid pyrite microcrystalline particle size on redox conditions were determined. In Penglai beach section GSSP identified 4 categories of 5 sub categories of habitat types, including type 2, type 1 and 2 type III, III, IV, and V habitat types reflected in Guadeloupe. At the end of the world in a regressive phase, and Leping early into transgression stage. The sea level low level corresponds to the extinction of the main period, causing marine benthic animal death. But the planktonic animals out, swimming class 缁濋珮宄板嚭鐜板湪娴峰钩闈�涓婂崌鏃舵湥�

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