摘要
白垩纪一古近纪之间(K/Pg,~65.5Ma)发生了显生宙以来的第五次生物大灭绝,其古环境、古气候的反演长期以来都是国内外的研究热点。四川盆地峨眉山地区保存了完整且连续的K/Pg陆相地层,是研究K/Pg界线的理想地区。本次研究作者采集了峨眉山地区下古新统名山组(E_(1-2)m)底部、K/Pg界线(层)、上白垩统灌口组(K2g)顶部的岩石样品,利用部分元素在剖面上的变化特征进行了古环境、古气候的综合分析。结果表明:研究区K/Pg界线处的砂岩具有明显铂族元素异常,Ir含量高达大陆地壳的216倍;根据Pb,K_(2)O/Na_(2)O,Rb/Sr,硅铝率、硅铝铁率等共计12个指标在剖面上的变化趋势,推断研究区在K/Pg过渡阶段的古气候最可能为:白垩世晚期温暖湿润,古新世早期炎热干燥,但两者过渡时的气候最炎热干燥,气候的急剧变化可能与此时的小行星撞击和德干火山喷发等极端因素有关。根据δCe,U/Th,V/Cr,Ni/Co,Sr/Ba共5个指标在剖面上的变化趋势,推断研究区在K/Pg过渡阶段的古环境为氧化环境。该研究不仅分析了K/Pg过渡时期的环境气候变化特征,也为未来全球气候变化的预测和应对提供了地质历史信息。
The fifth mass extinction since Phanerozoic occurred between Cretaceous and Paleogene(K/Pg,~65.5 Ma),and the inversion of palaeoenvironment and palaeoclimate has been a hot research topic at home and abroad for a long time.The Emei Mountain area of Sichuan Basin in China has preserved complete and continuous K/Pg continental strata,which is an ideal place to study the K/Pg boundary.In this paper,rock samples are collected from the bottom surface of the Lower Paleocene Mingshan Formation(E_(1-2)m),at the K/Pg boundary layer,and on the top surface of the Upper Cretaceous Guankou Formation(K_(2)g)along a section in Emei Mountain area.Thus,a comprehensive geochemical analysis is carried out on these samples to unravel the palaeoenvironment and palaeoclimate conditions in accordance with the variation characteristics of some elements in the profiles.The results show that the sandstone at the K/Pg boundary in the study area has obvious platinum group element anomaly,and the Ir content reaches up to 216 times that of continental crust.According to the variation trends of the 12 indexes in the profile,such as Pb,K_(2)O/Na_(2),Rb/Sr,Si/Al ratio,Si/Al/Fe ratio,the palaeoclimate of the study area during the K/Pg transition stage is most likely as follows.The palaeoclimate in Late Cretaceous was warm and humid,and in the early Paleocene,it was hot and dry.However,the transition period between the two was the hottest and driest.The dramatic changes in climate may be related to extreme factors such as asteroid impacts and Deccan volcanic eruptions at this time.According to the variation trend of Ce,U/Th,V/Cr,Ni/Co,Sr/Ba on the profile,the palaeoenvironment in the study area during the K/Pg transition stage was an oxidizing environment.This study not only analyzes the characteristics of environment and climate change during the K/Pg transition period,but also provides geological historical information for the prediction of and response to global climate change in the future.
作者
贺文霄
刘雪敏
江瑶
HE Wenxiao;LIU Xuemin;JIANG Yao(Sichuan Key Laboratory of Applied Nuclear Techniques in Geosciences,Chengdu University of Technology,Chengdu,Sichuan 610059,China)
出处
《矿物岩石》
CAS
CSCD
北大核心
2023年第3期60-72,共13页
Mineralogy and Petrology
基金
国家重点研发计划项目(编号:2016YFC0600604)
成都理工大学峨眉、马角坝基地建设专项基金项目(编号:11100-20Z06)。
关键词
四川盆地
K/Pg界线
古环境
古气候
元素地球化学
Sichuan Basin
K/Pg boundary
palaeoenvironment
palaeoclimate
element geochemistry
