CARBONATE PLATFORM DEPOSITS AND STRATIGRAPHIC SEQUENCES OF THE DENGYING FORMATION IN THE NANHUA AREA,NORTHERN HUBEI

According to the features of the sedimentary facies and faCies associations,the carbonaterocks of the Dengying Formation in the Nahua area ,northern Hubei,are divided,from the bot-ton to the top,into three sedimentary facies belts: evaporite platform,restricted platform tidalflat,and open platform largoon. This pattern of environmental evolution indicates a generaltrend of slow sea-level rise. Study of sequence stratigraphy shows that two stratigraphic se-quences can be recognized in the Dengying Formation,and both represent a secondary fluctua-tion on the background of slow rise during the late part of the Late Sinian,The duration（ca.tens of millions of years）and rate（ca. a few of tens of mm/1000 yr）of sea-level rise of eachsecondary to the 2nd-and 3rd-order cyclic sea-level change.