Geochronostratigraphy and Relationship of the Late Mesozoic Terrestrial Lithostratigraphic Units in South China
LI Xianghui;ZHANG Chaokai;WANG Yin;LIU Ling;School of Earth Sciences and Engineering,Nanjing University;East China Mineral Exploration and Development Bureau;
The precise age and correlation of the Late Mesozoic terrestrial lithostratigraphic units in South China have long been in dispute.Based on the summary for the zircon U-Pb isotope age data of volcanic rocks published in recent years,along with complementary work in this study,this study revised and determined the ages and relationship of the lithostratigrapic units in the Late Mesozoic terrestrial volcano-sedimentary basin in the Gan-Hang tectonic zone,South China.Some preliminary understanding in five aspects has been made as follows.(1)In western Zhejiang,the Moshishan Gr(Group),Jiande Gr,and Yongkang Gr were probably formed in early and middle Early Cretaceous(～145～120 Ma and～140～115 Ma),and late Early Cretaceous(～125～105 Ma),respectively,indicating they formed in a chorological order with parts co-existing.Laterally superimposed relation occurs among the formations of the Jiande Group and the formations of the Yongkang Group.The age(98 Ma)of zircons from the lower Zhongdai Formation indicates that the Qujiang Group had started since the beginning of Late Cretaceous.The two typical sections,located at Shouchang of Jiande basin and Laozhu of Lishui basin respectively,all consist of two similar stratigraphical sequences.(2)The Yong'an basin in western Fujian may have the oldest stratum record in Late Mesozoic era,with the Douling Group forming in Late Jurassic to early Early Cretaceous(～162～125 Ma)and the Shimao Formation in middle to late Early Cretaceous(～135～95 Ma).The Shaxian Fm of the Chishi Gr has a time range from late Aptian to early Cenomanian(～115～93 Ma),the Baiyashan Fm has a short age duration(～100～97 Ma),and the Chong'an Fm could have not started until～100 Ma.The study suggest that not only an up-down relationship but also more coeval different lithofacies with lateral progradation occur between the Bantou Fm and Xiadu Fm,the Zhaixia Fm and Huangkeng Fm,and among the Shaxian,Junkou,Baiyashan and Chong'an formations.(3)In eastern Jiangxi,the Wuyi Gr formed in early Early Cretaceous(～145～125 Ma),the Huobashan Gr might no begin until the early Aptian(～122 Ma),the Ganzhou Gr could be deposited after early Albian(～110 Ma),and the Guifeng Gr might start in early Late Cretaceous(after～100 Ma).The study suggests that the main sequences among the Daguding,Eheling and Shixi formations,and Hekou and Tangbian formations are contemporaneous heterotopic facies in different environment,likely with lateral superimposition.While the Luotang,Lengshuiwu and Zhoujia formations,and Hekou and Lianhe formations are probably the same sequences but named differently.(4)The Late Mesozoic strata in the Gan-Hang tectonic zone can be classified into three stages:stage I,the early Early Cretaceous volcanic squence;stage II,the late Early Cretaceous volcano-sedimentary squence;and stage III,the Late Cretaceous sedimentary squence.Corresponding sequence record may be grouped into one supergroup,and the evolution stages of three strata to some extent reflect three tectonic evolution stages.(5)The extensive lateral superimposition and facies elationship of lithostratigraphic units of formations in the GanHang volocano-sedimentary basin suggests that it is necessary to revise and reinterpret the successive and progradational relationships of the late Mesozoic terrestrial lithostratigraphic units in South China.
【Fund】： 国家重点基础研究发展计划(973)项目“晚中生代温室地球气候-环境演变”(编号2012CB822000)课题“晚中生代东亚地区古气候重建”(编号2012CB822003);; 国家自然科学基金项目“华南白垩纪-古近纪气候变化及定量重建(编号41372106)”联合资助的成果
【CateGory Index】： P534.5;P597.3
【CateGory Index】： P534.5;P597.3