本文選題：蓬萊灘GSSP剖面　切入點(diǎn)：G-L界線　出處：《東華理工大學(xué)》2017年碩士論文

【摘要】：瓜德魯普末期發(fā)生了一次大規(guī)模的生物滅絕事件。關(guān)于該次生物滅絕的原因,前人給出了包括海洋缺氧,峨眉山玄武巖噴發(fā)、全球性海平面下降以及卡穆拉變冷事件等不同的解釋。其中海洋缺氧被認(rèn)為是生物滅絕的致死原因,關(guān)于G-L界線海水的氧化還原條件已有研究者做了部分研究工作,但多數(shù)研究剖面G-L界線生物記錄不夠完整,氧化還原條件的變化還需不同的氧化還原指標(biāo)來進(jìn)行討論。本文對廣西來賓蓬萊灘GSSP剖面瓜德魯普統(tǒng)茅口組至樂平統(tǒng)合山組地層進(jìn)行系統(tǒng)的野外勘察,詳細(xì)分析卡匹敦期至吳家坪早期的生境型變化、黃鐵礦形態(tài)以及草莓狀黃鐵礦粒徑和微晶粒徑特征。根據(jù)生境型變化和黃鐵礦形態(tài)特征分別討論卡匹敦期至吳家坪早期的海平面變化和氧化還原條件,從而探討海平面變化和海洋缺氧對生物滅絕的影響。并綜合分析廣西來賓蓬萊灘GSSP剖面、湖北恩施田鳳坪剖面和四川廣元肖家壩剖面的草莓狀黃鐵礦微晶粒徑特征,根據(jù)草莓狀黃鐵礦微晶粒徑對氧化還原條件進(jìn)行厘定。在蓬萊灘GSSP剖面上共識別出4個大類5個亞類生境型,包括Ⅱ2型、Ⅲ1型、Ⅲ2型、Ⅳ型、和Ⅴ型。生境型反映了在瓜德魯普末期全球處于海退階段,而樂平早期則變?yōu)楹Ｇ蛛A段。海平面較低水平對應(yīng)著該時期主要的生物滅絕,造成海洋底棲類動物的死亡。但浮游、游泳類動物的滅絕高峰出現(xiàn)在海平面上升時期。說明瓜德魯普末期海平面下降至少不是該時期生物滅絕的唯一原因。茅口組下部不含草莓狀黃鐵礦,黃鐵礦以自形晶為主;中部的草莓狀黃鐵礦粒徑平均值為5.86~10.20μm,大部分樣品粒徑最大值大于20μm,并且在Jinogondolella xuanhanensis牙形刺帶頂部出現(xiàn)粒徑小,變化范圍窄的樣品;上部缺少草莓狀黃鐵礦,以自形晶黃鐵礦和過大生長的草莓狀黃鐵礦為主;茅口組頂部至合山組富含粒徑較小的草莓狀黃鐵礦,大部分樣品粒徑最大值小于18μm,間歇性出現(xiàn)一些粒徑小,變化范圍窄的樣品。這表明茅口早期(Jinogondolella shannoni牙形刺帶)沉積水體為氧化的環(huán)境;中期(Jinogondolella altuaensis-Jinogondolella xuanhanensis牙形刺帶)為長期貧氧環(huán)境,并在Jinogondolella xuanhanensis牙形刺帶結(jié)束時期出現(xiàn)短期缺氧;茅口晚期為氧化至貧氧環(huán)境;茅口末期至吳家坪早期為缺氧環(huán)境中間歇性出現(xiàn)硫化或氧化-貧氧環(huán)境。出現(xiàn)缺氧層位與出現(xiàn)生物滅絕事件的層位相對應(yīng)。硫化海水的上涌可以引起淺海底棲生物出現(xiàn)死亡,海洋缺氧很可能是導(dǎo)致瓜德魯普末期生物滅絕的主要原因。在硫化環(huán)境中形成的草莓狀黃鐵礦微晶粒徑平均值一般小于0.68μm,標(biāo)準(zhǔn)偏差一般小于0.3μm;而氧化至貧氧環(huán)境中形成的草莓狀黃鐵礦微晶粒徑平均值一般大于0.86μm,標(biāo)準(zhǔn)偏差一般大于0.5μm。所以草莓狀黃鐵礦微晶粒徑也可以用以指示氧化還原條件,在其標(biāo)準(zhǔn)偏差與平均值的交匯圖中可以劃分出硫化-缺氧環(huán)境、氧化-貧氧環(huán)境區(qū)域,以及兩者之間的過渡帶。
[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 緇濋珮宄板嚭鐜板湪嫻峰鉤闈笂鍗囨椂鏈，

本文編號：1660652