川东北地区中侏罗世新田沟期古气候波动的地球化学响应  

Geochemical response to paleoclimate fluctuation during Xintiangou Period(Middle Jurassic),Northeastern Sichuan

作　　者：陈晓慧[1] 曾建理 张廷山[1] 祝海华[1] 张婧璇 李世鑫 李耀羽 CHEN Xiaohui;ZENG Jianlin;ZHANG Tingshan;ZHU Haihua;ZHANG Jingxuan;LI Shixin;LI Yaoyu(School of Geosciences and Technology,SW Petroleum University,Chengdu,6l0S00,China;School of Civil Engineering,RMIT University,Melbourne 3001,Australia)

机构地区：[1]西南石油大学地球科学与技术学院,成都610500 [2]皇家墨尔本理工大学土木工程学院,澳大利亚墨尔本3001

出　　处：《地质学报》2019年第12期3223-3238,共16页Acta Geologica Sinica

基　　金：自然基金项目（编号41972120,41272135）;现代古生物学和地层学国家重点实验室开放基金项目（编号173131）资助成果

摘　　要：四川盆地中侏罗统新田沟组作为侏罗纪大面积红层之下的重要岩石地层单元,见证了盆地由潮湿向干旱转变的整个过程。然而,以往的研究主要集中在古气候类型方面,缺乏系统深入的气候变化研究。本文以川东北地区宣汉七里乡塔坝剖面为对象,系统分析了泥岩的主微量元素地球化学特征,结果表明:化学蚀变指数(CIA)、C值、Sr/Cu、Sr/Ba、Rb/Ti、Cs/Ti、Rb/K等7种古气候替代指标综合显示新田沟期气候存在从炎热潮湿逐渐向干旱转变的趋势,整体以半干旱-半潮湿气候为主。且该时期气候变化过程并不稳定,存在多个短期的湿热与干旱的气候波动。在新田沟组沉积末期,气候条件变得极端干燥。川东北地区中侏罗世的元素地球化学特征记录了区域内重大地质转折期将至时的气候变化,在侏罗纪大面积红层发生之前,气候条件已经开始响应。在中侏罗世早期,四川盆地与欧洲地区并不处于同一个气候带内。Xintiangou Formation is a key stratigraphic interval beneath the wide-spread Jurassic red strata in the Sichuan basin, and records the climatic change from humidity to drought in the early Middle Jurassic. However, previous researches focused mainly on palaeoclimate patterns, and lack of deep and systematic study of climatic change. This paper investigated geochemical characteristic of mudstone from the Taba section of the Middle Jurassic Xintiangou Formation. The results show that seven climatic proxies(CIA, C-value, Sr/Cu, Sr/Ba, Rb/Ti, Cs/Ti, Rb/K) are indicative of the palaeoclimate change from hot and humid to drought, and dominantly semi-arid-semi-humid climate. However, the process of the climate change was not stable, fluctuating in several hot/humid and dry periods. At the end of the Xintiangou Formation sedimentary period, climate condition became extremely dry. The geochemical characteristics of the Xintiangou Formation mudstones in the northeastern Sichuan Basin records the climate changes at a crucial turning point of geological history, indicating that the climate started to respond before occurrence of large-scale deposition of Jurassic red bed. During the early Middle Jurassic, the Sichuan basin was no in the same climate zone as the Europe.

关 键 词：元素地球化学 古气候 早侏罗世 新田沟组 川东北 

分 类 号：P61[天文地球—矿床学]