广西横县六景泥盆系艾菲尔阶—吉维特阶之交化学地层研究  

Chemostratigraphy of Eifelian--Givetian Stage Boundary at Liujing Section,Guangxi,South China

作　　者：刘疆[1] 白志强[1] 

机构地区：[1]北京大学地球与空间科学学院,北京100871

出　　处：《地质论评》2008年第5期683-693,I0004,共12页Geological Review

基　　金：国家自然科学基金(编号40372018)的成果

摘　　要：内容提要:广西横县六景泥盆系剖面艾菲尔阶—吉维特阶界线(Eifelian—Givetian界线)附近的Polygnathus xylus ensensis至下varcus带之间,出现了一系列Ce/La值、Ni/La值和δ^(13)C_(carb)值重大组合性异常,分别代表缺氧事件、Ni事件和生物灾变等地质历史事件。紧邻艾菲尔阶—吉维特阶界线的生物事件与全球性ka(?)k-otomari事件有较好的响应。该地区所处华南地块南侧、古特提斯洋离散边界附近的古陆缘浅海为上述事件的古地理、古大地构造背景。该系列事件的原始诱因为系列构造运动的不同阶段和不同表现方式:断裂和火山热液活动造成Ni事件;挤压变形和抬升运动耦合相对海平面变化造成缺氧事件。Ni事件和缺氧事件均可独立造成生物灾变事件,而前二者的叠加将使生物灾变加剧,因灾变机制的区域性而未造成生物的大规模灭绝。Ni事件是由洋源性构造、热液和火山活动所主导的。This study represents the chemostratigraphical work on limestones covering the Polygnathus xcylus ensensis to lower varcus Zones at Liujing section, Guangxi, south China. In conjunction with biostratigraphic ahservations, values/contents and trends of Ce/La, Ni/La, δ^13Ccarb of unaltered limestones presented in this study provide the most powerful bioehemostratigraphie tool in recognizing a series of anoxic events, Nickel-events and bio-events. Together with the large positive excursion of δ^13Ccarb just on the Eifelian--Givetian boundary reflecting higher productivity and burial of organic matter, the essentially pronounced negative excursions near the boundary relating to the global kacák-otomari event are well correlated by those of Volf Gorge and U dubu sedmi bratri in the Barrandian basin, Czech Republic. The paleogeographical and paleotectonic locations, the shallow sea to the south boundary of South China Massif, the dispersing-boundary of paleo Tethys were the oceanographic background of these events. The faults, rifts and volcanoes triggered Nickel-events, while up-lifting movements and the fluctuating RSL were expressed by anoxic events. Nickel events and anoxic events could lead to bio-events independently, while the conjunction of them made bio-events much heavier. Mass-extinction hadn＇t been inferred on a large scale because of the regional mechanism and extent of the events. The Nickel-events was of an oceanographic characteristic.

关 键 词：中泥盆统 艾菲尔阶 吉维特阶 界线 化学地层 事件 广西 六景 

分 类 号：P539.7[天文地球—古生物学与地层学]