FEATURES OF GRAVITY CURRENT DEPOSITS OF THE CARBONATE PLATFORM SUBSIDE IN THE FIRST MEMBER OF THE TONGZI FORMATION IN WESTERN HUBEI

Gravity current deposits of the carbonate platform subside in the first member of the Ordovician Tongzi Formation in Zigui,Changyang and Badong,western Hubei,fall into four types:（1） collapse breccia;（2）debris flow calcirudite limestone;（3）grain flow pebbly calcarenite limestone;and （4）proximal turbidity limestone The platform subside gravity current deposits furnish stratigraphic records of the precursory,episodic events of evolution from the Early Ordovician South China passive continental margin to the foreland basin in the carbonate platform It mainly discusses the setting,origin and constrains of gravity current deposits of the Ordovician Lianghekou’an carbonate platform subside in western Hubei and even in the Upper Yangtze region as well as the significance of their study