Sedimentary Characteristics and Its Geological Implications of Cambrian Tempestite in Northern Henan Province

Cambrian in northern Henan Province is mainly composed of carbonate rocks and mudstones.Several storm deposits or tempestite are developed in Mantou Formation,Zhangxia Formation,Gushan Fm.and Chaomidian Formation of Cambrian.The storm sedimentary structures include erosional structures in the bottom surface(gutter structure),storm-tearing structures,storm-whirlpool structures(calcirudite with radial framework and ring structures),storm-wave structures(hummocky cross bedding).Storm deposits among Mantou Formation,Gushan Formation and Chaomidian Formation form in shallow sea area between fair-weather wave base and storm wave base.Storm deposits of Zhangxia Formation are formed in nearshore area above fair-weather wave base.They mainly consist of three types of lithofacies: ① calcirudite with the massive bedding;② calcirudite and calcarenite with hummocky cross bedding;③ micrite with homogeneous bedding.The lithofacies above represent respectively deposits of storm eddy(①),deposits of storm wave(②) and rapid suspended deposits in the late stage of a storm(③).The lithofacies can be categorized into different storm sedimentary sequence.The discovery of the storm deposits shows that northern Henan Province was located in the low-latitude area during Cambrian.The sediments are of great significance to explain the Cambrian palaeogeography,palaeoclimate and paleoceanography of North China.