鄂西秭归盆地下侏罗统香溪组泥岩地球化学特征及其古环境意义  

GEOCHEMICAL CHARACTERISTICS AND PALEOENVIRONMENTAL SIGNIFICANCE OF MUDSTONES FROM THE LOWER JURASSIC XIANGXI FORMATION IN THE ZIGUI BASIN, WESTERN HUBEI PROVINCE, CHINA

作　　者：代军 王永栋 周宁[3,4] 李丽琴[3] DAI Jun;WANG Yong Dong;ZHOU Ning;LI Li Qin(School of Earth Sciences and Engineering,Nanjing University,Nanjing 210023;Centre for Research and Education on Biological Evolution and Environment,Nanjing University,Nanjing 210023;State Key Laboratory of Paleobiology and Stratigraphy,Nanjing Institute of Geology and Palaeontology andCenter for Excellence in Life and Paleoenvironment,Chinese Academy of Sciences,Nanjing 210008;Department of Geology,Northwest University,Xi’an 710069)

机构地区：[1]南京大学地球科学与工程学院,江苏南京210023 [2]南京大学生物演化与环境科教融合中心,江苏南京210023 [3]中国科学院南京地质古生物研究所和生物演化与环境卓越创新中心,现代古生物学和地层学国家重点实验室,江苏南京210008 [4]西北大学地质系,陕西西安710069

出　　处：《地层学杂志》2021年第1期58-68,共11页Journal of Stratigraphy

基　　金：中国科学院战略性先导科技专项(B类)(XDB26010302);国家自然科学基金(41790454、41572014);青年科学基金(42002001);现代古生物学和地层学国家重点实验室(20191103、203126)共同资助。

摘　　要：泥岩中主量元素、微量元素的变化与沉积环境和古气候的变化息息相关。本文利用XRF和ICP-MS等技术手段分析了鄂西秭归地区头道河剖面下侏罗统香溪组泥岩中的主量元素和微量元素,揭示香溪组沉积时期的沉积环境和古气候特征。头道河剖面香溪组上段第1—12层Sr含量均值为113.8×10^(-6),第13层均值骤增为2838.3×10^(-6),指示水体盐度大幅上升, Ba含量及Sr/Ba比值变化指示了相同的结果。这可能是由于香溪组沉积晚期气候变得炎热干旱,水体蒸发量迅速增大导致。Ni/Co、Cu/Zn及Ceanom等指标指示香溪组沉积水体介质由早期的富氧条件转变为晚期的还原条件。Sr、Mg/Ca及CIA等指标反映了香溪组沉积晚期发生了气候升温干热化事件。这些元素分析结果揭示了香溪组上部炎热干旱的古气候特征,可能与早侏罗世托阿尔期(Toarcian)缺氧事件(T-OAE)有关。The changes of major elements and trace elements in mudstone are closely relate to sedimentary environment and paleoclimate. We use XRF and ICP-MS to analyze the major and trace elements of mudstones from the terrestrial Lower Jurassic Xiangxi Formation in the Toudaohe section of the Zigui Basin, western Hubei Province, China in order to recover the sedimentary environment and palaeoclimate conditions. The mean Sr content is 113.8 ppm for the basal 12 layers of the upper Xiangxi Formation but rises to 2838.3 ppm for the 13th layer, indicating a sudden increase in water salinity. And the changes in Ba content and Sr/Ba ratio show the same results. Indicators such as Ni/Mo, U/Th, V/Cr, Cu/Zn and Ceanom suggest that the sedimentary water medium changed from oxygen-rich condition during the early depositional stage of the upper Xiangxi Formation to reduction condition during the late stage. Indicators such as Sr, Mg/Ca, CIA reflect the occurrence of dry heating events when the upper Xiangxi Formation was deposited. These results reveal a dry heat paleoclimate during the deposition of the upper Xiangxi Formation in the Zigui Basin, which was possibly related to the Early Jurassic Toarcian Anoxia Event(T-OAE).

关 键 词：早侏罗世 香溪组 秭归盆地 地球化学 古气候 湖北 

分 类 号：P534.52[天文地球—古生物学与地层学]