古地貌对陆相裂谷盆地层序充填特征的控制——以渤中凹陷西斜坡区下第三系为例

构造运动造就的古地貌在陆相盆地 ,特别是裂谷盆地对层序形成与发育起着重要的控制作用。裂陷扩张早期 ,凸起前发育下切河谷充填作用 ,前缘发育扇三角洲体系 ;当陆源碎屑补给缺乏时 ,局部隆起的水下平台区发育滨、浅湖滩坝或生物碎屑滩体系。裂陷扩张早中期 ,基准面上升时期凸起区为盆地主要物源区。受长期活动的边界基底断裂规模、性质、活动强度的控制 ,盆地边缘发育 3种类型的古地形坡折带 ,分别控制 3种类型沉积体系的形成。断崖型坡折带发育近岸水下扇沉积体系 ;断阶型坡折带发育斜坡扇体系 ;陡坡型坡折带发育扇三角洲及前方的盆底扇体系。基准面下降时期盆地充填作用增强 ,受凸凹相间分布的宏观地貌特征控制 ,凸起前缘发育扇三角洲体系 ,凸起间鞍部地区沿盆地长轴方向发育外源大型河流 -三角洲体系。

CONTROL OF PALEO-MORPHOLOGY TO STRATIGRAPHIC SEQUENCE IN CONTINENTAL RIFT BASINS: TAKE LOWER TERTIARY OF WESTERN SLOPE IN BOZHONG DEPRESSION AS AN EXAMPLE

Paleo morphology resulted from tectonic movement controlled the sequence formation and development of continental basins,especially of rift basins.In the early spreading stage of a rift basin,incised channel fillings and fan deltas developed in front of uplifts;shallow lake bars or bioclastic banks developed on locally uplifted subaqueous platform.In the early middle spreading stage,base level rose,the uplifts turned to be the main provenances,three types of break in slopes developed on the basin margin,which resulted in three types of depositional systems.Nearshore subaqueous fan system resulted from faulted scarp type break in slope;slope fans system developed on faulted terrace type break in slope;fan deltas and sub lake fan system developed on steep slope type break in slope.In base level falling stage,the rift basin was gradually filled by fan deltas and fluvial delta systems.