沉积与特提斯地质2025，Vol.45Issue(1)：14-30,17.DOI:10.19826/j.cnki.1009-3850.2024.09003
南秦岭北带三叠纪盆地古气候、古海洋、古环境演化研究
Study on paleoclimatic,paleoceanic,and paleoenvironmental evolution of the Triassic basin in the northern belt of the South Qinling
摘要
Abstract
On the basis of field geological investigations,the sedimentary facies of outcrops were studied,and sedimentary facies types were classified based on the results of particle size analysis.Additionally,through major and trace element analyses of sandstone samples,and C-O isotope analysis of carbonate rocks,the process of paleoclimatic,paleoceanic,and paleoenvironmental evolution in the Triassic basin was discussed.The results show that:(1)From bottom to top,the Triassic strata in the study area consist of open platform carbonate rocks of the Lower Triassic Zhalishan Formation and Malasongduo Formation in the southern part of the basin,semi-deep sea slope facies of the Longwuhe Formation,shallow marine shelf facies of the Middle Triassic Guojiashan Formation,semi-deep sea shelf slope facies of the Guanggaishan Formation,and shallow marine shelf facies of the Upper Triassic Daheba Formation;(2)Values of the chemical index of alteration(CIA),index of compositional variability(ICV),and the relationship between Rb/Sr and K2O/Al2O3 ratios in sandstone samples indicate that the Triassic period in the study area experienced two major paleoclimatic shifts:from warm and humid to semi-arid and arid conditions,which caused changes in the paleobasin's water depth,fluctuating from deeper to shallower stages,and influenced the salinity of the water.The precipitation brought by the warm and humid climate greatly reduced the salinity of seawater,while the hot semi-arid and arid climate greatly increased the salinity of seawater.(3)The paleowater body developed in the Triassic sandstone in the study area presents a weakly oxidizing environment,which is conducive to the development and flourishing of aquatic organisms.This environment provided a basis for the formation of sedimentary organic matter,though it was not ideal for the preservation of sedimentary organic matter due to the oxidizing conditions.关键词
南秦岭北带/三叠纪盆地/古气候/古海洋/古环境Key words
northern belt of the South Qinling/Triassic basin/palaeoclimate/paleoceanography/palaeoenvironment分类
地质学引用本文复制引用
霍勤知,徐磊,白云来,刘明..南秦岭北带三叠纪盆地古气候、古海洋、古环境演化研究[J].沉积与特提斯地质,2025,45(1):14-30,17.基金项目
中国地质调查局项目(2017-01-15-02-02) （2017-01-15-02-02）
