通过对川南地区长宁区块上奥陶—下志留统龙马溪组地层的总有机碳含量(Total Organic Carbon，TOC)、主量元素及微量元素分析，对长宁地区A1 井页岩层序进行新的划分，其中龙一 1 为海侵体系域(Transgressive System Trace，TST)和早期高位体系域(EHST-1 和EHST-2)，龙一 2 为晚期高位体系域(Late Highstand Systems Tract，LHST)，并揭示了古海洋氧化还原环境(用U/Th、V/Cr、Ni/Co、MoEF-UEF表示)、古生产力(用Babio、Ti、Al、Siex表示)、陆源碎屑输入(用总有机碳含量TOC、Ti、Zr和Al等表示)、古气候(以蚀变化学指数CIA，成分变化指数ICV)、原岩类型(用Th/Sc-Zr/Sc、SiO2/Al2O3-K2O/Na2O、La/Th-Hf、Co/Th-La/Sc等表示)、有机质富集控制因素(用UEF、TOC、Mo/Al、Siex表示)和水体滞留环境(用Co×Mn、Al、TOC表示)等参数的变化。研究结果显示，鲁丹阶TST时期海平面升高，上扬子地区水体普遍缺氧，持续的上升洋流带来大量的营养物质进入海水，导致古生产力大幅度提高。强烈构造沉降和化学风化的减弱及海平面升高共同导致汇水区的陆源碎屑供给较低。因此，古生产力、氧化还原条件为鲁丹阶TST时期有机质富集主控因素，碎屑供给为次要控制因素。由于气候及古地理环境存在显著差异，EHST-1、EHST-2 及LHST时期，有机质富集主控因素是氧化还原条件及碎屑供给，古生产力为次要控制因素。
Rhuddanian-Aeronian Paleogeographic Shifts in Southern Sichuan Basin:Implication for Shale Gas Sweet Spot Exploration
Through the analysis of total organic carbon(TOC),major,and trace elements in the Upper Ordovician to Lower Silurian Longmaxi Formation strata of the Changning Block in southern Sichuan,we have redefined the shale sequence stratigraphy for Well A1 in the Changning area.This reclassification delineates Long 1 layer into the Transgressive System Tract(TST)and Early Highstand System Tracts(EHST-1 and EHST-2),with Long 2 layer categorized as the Late Highstand System Tract(LHST).Our findings underscore the variability in ancient marine redox conditions,paleoproductivity,terrigenous detrital input,paleoclimate,protolith types,factors controlling organic matter enrichment,and water column stratification.The research reveals that during the Ludian TST,sea level rise led to widespread hypoxia in the Upper Yangtze region,with substantial nutrient influx from upwelling currents,significantly boosting paleoproductivity.Intense tectonic subsidence,diminished chemical weathering,and sea level rise collectively resulted in lower terrigenous detrital input.Thus,paleoproductivity and redox conditions were the primary drivers of organic matter enrichment during the Ludian TST,with detrital supply as a secondary factor.Due to significant climatic and paleogeographic differences,redox conditions and detrital supply were the primary enrichment factors during the EHST-1,EHST-2,and LHST periods,with paleoproductivity playing a secondary role.
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