四川盆地中部中侏罗统沙溪庙组沉积期古环境与古气候演化——以永浅1井为例

四川盆地中部中侏罗统沙溪庙组沉积期古环境与古气候研究对揭示该时期盆内的沉积格局、重建古地理及油气形成与演化具有重要的理论和实践意义。本文以四川盆地中部永浅1井的47件泥岩样品为研究对象，通过主微量元素的变化特征恢复研究区沙溪庙组沉积期的古环境与古气候演化过程。研究结果表明，Sr/Ba比值、Rb/K2O比值、Ca/Mg比值和Ca/(Ca+Fe)比值指示川中地区中侏罗统沙溪庙组沉积期整体为淡水环境，但在沙溪庙组一段沉积中、晚期出现了短暂的水体盐度升高；V/(V+Ni)比值、U/Th值、V/Cr比值与Ni/Co比值指示沙溪庙组沉积期整体为间歇暴露的浅水氧化环境，局部为弱氧化或还原环境；C值、CIA值和Rb/Sr比值等指标显示，沙溪庙组沉积期古气候总体为温暖湿润的气候环境，但期间发生波动性干旱，在温暖湿润和半干旱—半湿润之间频繁波动。多元地球化学参数为川中地区中侏罗统沙溪庙组沉积期的古气候演化和区域性古气候对比提供了新的证据。

Paleoenvironment and paleoclimate evolution during the depositional period of the Middle Jurassic Shaximiao Formation in the central Sichuan basin: A case study of well Yongqian 1

The study of the paleoenvironment and paleoclimate during the depositional period of the Middle Jurassic Shaximiao Formation in the central Sichuan basin has important theoretical and practical implications for revealing sedimentary patterns, reconstructing paleogeography, and understanding the oil and gas formation and evolution within the basin during that period. This paper analyzed 47 mudstone samples obtained from well Yongqian 1, utilizing variations in major and trace elements to reconstruct the paleoenvironment and paleoclimate evolution. The results show that the Sr/Ba ratio, Rb/K2O ratio, Ca/Mg ratio, and Ca/(Ca+Fe) ratio indicate that the Middle Jurassic Shaximiao Formation was mainly deposited in a freshwater environment. However, a temporary increase in salinity occurred in the middle and late depositional periods of the first member of the Shaximiao Formation. The V/(V+Ni) ratio, U/Th ratio, V/Cr ratio, and Ni/Co ratio suggest that the Shaximiao Formation depositional period was generally characterized by shallow water oxidizing conditions with intermittent exposure and localized weakly oxidizing or reducing environments. The C value, CIA value, and Rb/Sr ratio indicate that the paleoclimate during the Shaximiao Formation depositional period was predominantly warm and humid but experienced intermittent fluctuations, ranging from warm and humid to semi arid to semi humid conditions. The multivariate geochemical parameters provide new evidence for the paleoclimate evolution of the Middle Jurassic Shaximiao Formation during its depositional period in the central Sichuan basin, which is beneficial for the regional paleoclimate comparison.