龙门山山前带侏罗系近源冲积体系沉积特征与成因模式

Sedimentary characteristics and genetic model of Jurassic alluvial deposits in piedmont zone of Longmen Mountain

于海跃 尹伟 刘君龙2

中国石油大学（北京）油气资源与探测国家重点实验室，北京 102249 中国石化石油勘探开发研究院，北京 100083

State Key Laboratory of Petroleum Resources and Prospecting, College of Geosciences, China University of Petroleum, Beijing 102249, China Exploration & Production Research Institute, SINOPEC, Beijing 100083, China

基于高分辨率层序地层学理论，综合利用野外露头剖面、钻井剖面、岩心、地球物理、分析化验和测录井等资料，对龙门山山前带侏罗系沙溪庙组地层沉积相进行综合研究。结果表明：沙溪庙组发育冲积扇及辫状河三角洲2种沉积相类型；受古沉积环境的影响，沙溪庙组沉积经历了水体由浅变深、再变浅的演化过程；沙溪庙组发育2个方向的物源体系，短轴方向的物源主要来自龙门山，近长轴方向的物源来自龙门山北段；受物源和古地形的控制，龙门山北段的山前带主要发育辫状河三角洲沉积相，龙门山中—南段的山前带自北西到南东主要发育冲积扇￣辫状河三角洲沉积相。

Based on the theory of high-resolution sequence stratigraphy, the sedimentary facies of the Jurassic Shaximiao Formation in the study area were studied by the comprehensive application of outcrop profiles, seismic section, seismic amplitude image, core and drilling data. The results show that there are two kinds of depositional facies in this region, including alluvial fan and braided river delta. Under the influence of paleo-environment, the lake level of the Jurassic Shaximiao Formation in the study area experienced the evolution process from shallow to deep, and then became shallow. During this period, two types of provenance systems were primarily developed in the study area, i.e., short axis provenance from Longmen Mountain and approximate long axis provenance from northern Longmen Mountain. Under the influence of provenance and paleo-topography, the braided river delta was mainly developed in the northern Longmen Mountain Thrust Belt, while the alluvial fan-braided river delta was mainly developed in the central-southern Longmen Mountain Thrust Belt because of provenances and the ancient landform.

10.6056/dkyqt201903001