冀西北赤城—宣化盆地土城子组沉积特征及盆缘构造分析

Analysis of Depositional Characteristics of Tuchengzi Formation and Basin Edge Structures,Chicheng-Xuanhua Basin,Northwestern Hebei Province

为了揭示华北北部晚侏罗世沉积盆地性质,对赤城—宣化盆地中土城子组沉积特征及盆缘构造进行了研究。通过对土城子组沉积特征研究表明,土城子组中—下部为一套河湖相沉积,上部为一套冲积扇粗碎屑沉积;土城子组砾岩成分系统统计分析显示,赤城盆地与宣化—下花园盆地具有相似岩屑岩性相旋回,反映源区具有相同或相近的蚀顶过程。研究区晚侏罗世盆地中土城子组充填特征及盆缘构造特征表明,土城子组形成于挤压构造背景,土城子组沉积时期盆地受控于盆缘逆冲断层。大地构造背景暗示,赤城—宣化盆地晚侏罗世—早白垩世期间,古太平洋板块向NW方向的俯冲作用与尚义—赤城断裂向南逆冲并伴随右旋走滑作用是土城子组沉积时期盆地格局形成的重要控制因素。

In order to reveal the nature of the Late Jurassic basin in the northern part of North China,we studied the depositional characteristics of Tuchengzi Formation and the pattern of basin edge structures.The depositional characteristics of Tuchengzi Formation indicate that,the sediments in middle and lower parts of the formation are fluviolacustrine facies,and the upper are coarse clastic sediments in alluvial fan.The systematically statistical analysis of components of conglomerates in the Tuchengzi Formation show that,Chicheng basin and Xuanhua-Xiahuayuan basin are similar in the cuttings lithology cycle,this similarity indicates that both of the basins went through similar piecemeal stoping process.Combined depositional characteristics of Tuchengzi Formation with the characteristics of the basin edge structure indicate that, Tuchengzi Formation formed in the compressive tectonic background,and the evolutionary process of basin was controlled by basin margin thrust faults.The tectonic background of the areas indicates that,it＇s the NW-trending subduction of the Paleo-Pacific plate and the S-trending thrusting of the Shangyi-Chicheng thrust belt with a dextral strike slip component that controlled the formation of basin framework during the deposition of Tuchengzi Formation.