Formation and distribution of the biogenic limestones from the Palaeogene Shahejie Formation in the Huanghua depression

The biogenic limestones are developed in the lower "special lithologic part" of the first member of the Palaeogene Shahejie Formation in the Huanghua depression.They are scattered only in the Tangjiahe area in the northern part;concentrated in the Dazhongwang-Zhouqingzhuang-Wangxuzhuang-Koucun zone between Gangxi uplift and Kongdian uplift in the central part,and wide-spread in Cangzhou,Shenusi,Yanshan and Jibeitou-Dengmingsi regions in the southern part.The controlling factors of the distribution of the biogenic limestones in the study area include palaeoclimates,fossil water depth and medium conditions,slope gradient of palaeotopography and supply of terrigenous clastics.