摘要： 中侏罗统凉高山组是四川盆地重要产油气层系之一,其宏观沉积体系及其演化过程尚不明确,缺乏盆地级别沉积模式建立。基于轻重矿物、岩心、测录井、孢粉、微量元素及野外剖面资料,针对凉高山组各段沉积时期主要物源体系、古气候特征、沉积微相类型、沉积体系及演化过程进行了研究。结果表明: 四川盆地凉高山组沉积时期,发育龙门山中段和北段、米仓山、南秦岭、大巴山及雪峰古隆6个主要物源; 盆内气候早期炎热干旱,中期转变为温暖湿润气候,至晚期再次炎热干旱; 发育分流河道、分流河道间、水下分流河道、水下分流河道间、河口坝、席状砂、滨滨浅湖滩坝、浅湖泥及半深湖泥9类沉积微相; 凉高山组沉积时期,受周缘山系强弱交替隆升影响,盆地东部、东北部基底发生挠曲并快速沉降,形成大巴山前陆盆地,构成东陡西缓古构造格局及多物源供给体系; 受构造活动、 气候变化及古地貌影响,凉高山组沉积早期湖盆沉积与沉降中心均分布于川东、川东北地区;中期气候湿润,陆源输入增加,沉积中心迁移至川中地区,沉积与沉降中心发生错位;晚期湖盆填平补齐,逐渐萎缩。

关键词: 沉积模式, 沉积演化, 沉积相, 物源特征, 凉高山组, 中侏罗统, 四川盆地

Abstract:

The Middle Jurassic Lianggaoshan Formation in the Sichuan Basin is one of the key hydrocarbon-bearing strata;however,its macro-scale sedimentary systems and evolutionary processes remain poorly understood,and a comprehensive basin-scale sedimentary model is lacking. This study integrates data from heavy and light mineral analyses,core and well logs,palynology,trace elements,and field outcrops to investigate the provenance systems,paleoclimatic conditions,sedimentary microfacies types,sedimentary systems,and their temporal evolution across different depositional intervals of the Lianggaoshan Formation. The results identify six primary provenance areas active during the deposition of the Lianggaoshan Formation: the central and northern Longmen Mountains,the Micang Mountains,the southern Qinling Mountains,the Daba Mountains,and the ancient Xuefeng Uplift. The basin experienced a climatic transition from hot and arid conditions in the early stage,to warm and humid in the middle stage,and a return to hot and arid conditions in the late stage. Nine types of sedimentary microfacies were recognized,including braided channels,interdistributary areas,subaqueous distributary channels and interdistributary zones,estuarine bars,sheet sands,coastal and shallow lacustrine bars,shallow lacustrine mud,and semi-deep lacustrine mud. During the Lianggaoshan depositional period,alternating uplift of surrounding mountain ranges led to flexural subsidence of the eastern and northeastern basin basement,forming a foreland basin in front of the Daba Mountains. This process established a paleo-tectonic framework characterized by a steep eastern and gentle western margin,with multiple sediment source systems. In the early stage,both the depositional and subsidence centers were concentrated in eastern and northeastern Sichuan due to active tectonism,climate variation,and paleotopography. In the middle stage,increased humidity led to enhanced terrigenous input,and the depositional center shifted toward central Sichuan,resulting in a spatial offset between deposition and subsidence centers. By the late stage,the lake basin was filled and gradually contracted.

Key words: depositional model, sedimentary evolution, sedimentary facies, provenance, Lianggaoshan Formation, Middle Jurassic, Sichuan Basin

中图分类号: 

• P512.2