华北克拉通南部周口坳陷谭庄—沈丘凹陷早白垩世沉积、构造特征与原型盆地性质

谭庄—沈丘凹陷位于华北克拉通南部，大别山北缘与华北克拉通接壤部位的周口坳陷内。区内下白垩统地层厚度巨大，沉积和沉降中心偏于盆地南侧。沉积物以细粒陆源碎屑砂岩、粉砂岩和泥岩为主；岩石中富含火山碎屑，成分成熟度和结构成熟度中等；发育一系列牵引流成因的沉积构造，属于与河流三角洲——滨浅湖沉积体系及其沉积相的组合，早白垩世沉积物源供给主要来自南部。盆地的发育和演化及早白垩世沉积主要受南部边界的叶鲁断裂控制，属于张性正断层，后期该断层发生明显地向盆地方向的逆冲。依据下白垩统砂岩组分构造属性、砂岩岩屑组分、沉积物常量元素和稀土元素地球化学特征分析以及与南部大别山造山带火山岩发育年代的对比等综合分析认为，谭庄—沈丘凹陷形成于早白垩世伸展大地构造背景，是受大别山北缘山盆耦合作用影响形成的断陷型沉积盆地。

Sedimentary and Tectonic Features and Proto-basin of Early Cretaceous Tanzhuang-Shenqiu Sag, Zhoukou depression, in southern area of North China Craton

Located at the sourthern margin of the North China Craton, the Tanzhuang-Shenqiu sag, Zhoukou depression, is filled with Lower Cretaceous sediments in a huge thinckness. Deposits in the sag are characterized by thinner grained clastic rocks with miderteran composition and texture maturations, such as mudstone, siltstone and sandstone, and especially rich in volcanic clastics. Sedimentary structures and depositional facies associations interpreted as fluvial-delta and lacustrine environments were recognized in this research. Present study insisted that sediments supply of the Tanzhuang-Shenqiu sag in Early Cretaceous are from the Dabie orogenic belt to the south. Basin's Formation was initially controlled by the southern marginal stretch fault, I.e.,Yelu fault, which became thrusting toward north at the end of Early Cretaceous. Based upon study of sandstone composition and Q-F-L diagram (Dickinson's diagram), geochemistry of major and REE elements of sediments and the geochonology of volocanic rocks, writers suggest that the Tanzhuang-Shenqiu sag formed in a regional stretch tectonic setting in the Early Cretaceous, was a original fault basin.