江苏盐阜拗陷晚白垩世泰州组沉积相

Sedimentary facies of upper cretaceous Taizhou formation in the Yanfu depression, Jiangsu province

研究了盐阜拗陷晚白垩世泰州组沉积相类型、沉积特征,以及泰州组各亚段沉积相平面分布和盆地沉积演化规律. 结果表明:泰州组主要发育冲积扇、扇三角洲和湖泊3种沉积相,从盆地边缘到盆地中心,沉积相由冲积扇沉积渐变为扇三角洲或滨湖、浅湖、半深湖相沉积,自下而上由冲积扇沉积渐变为扇三角洲或滨湖,至浅湖、半深湖相,再到浅湖相沉积;晚白垩世泰州组沉积早期为断陷湖盆发育时期,以冲积扇、扇三角洲发育为特征,晚期为拗陷湖盆发育时期,湖平面持续上升,沉积范围扩大,浅湖相或半深湖相发育,而后湖平面下降,沉积物粒度变粗. 不同时期、不同地区的沉积特征表现各异,但总体表现出拗陷由小到大,再缩小的发育特点.

The types of sedimentary facies and the sedimentary characteristics in Taizhou Formation of Late Cretaceous System in Yanfu Depression are systematically analyzed, and the planar distribution of sedimentary facies in the members of Taizhou Formation and the laws of facies evolution are studied in detail. The conclusions show that Taizhou Formation is mainly composed of alluvial fans, fan deltas and lacustrine facies. In the basin, from the margin to the center, the facies developed from alluvial fans, gradually to fan deltas or lakefront facies, shallow-water lake facies, half-deep water lake facies; from the bottom to the top, the facies gradually changed from alluvial fans to fan deltas or lakefront facies, to shallow-water lake facies, hemi-deep-water lake facies, finally to shallow- water lake facies. The Taizhou Formation can be divided into two stages: early stage and later stage. In the early stage, it developed as fault lacustrine basin ,characterized by alluvial fans and fan deltas; in the later stage, it developed as depressive basin, lake surface kept increasing, the depth of the lake increased, the sediment area enlarged, and shallow-water lake facies or half-deep water lake facies developed. Henceforth, lake surface dropped and granularity of sediment become coarser. The sedimentary characteristics are correspondingly different in various stages and areas. But, as a whole, the Yanfu Depression changed from narrow to wide, and then to narrow.