MIDDLE AND LATE EARLY TRIASSIC SEDIMENTARY FACIES AND PALAEOGEOGRAPHY IN SOUTHEASTERN HUBEI

The Lower Triassic Daye Group dominated by the carbonate strata in southeastern Hubei may be divided into 10 lithologic members in the Xinwupu section, Yangxin County. The present paper gives an interpretation of the characteristics of the middle and late Early Triassic sedimentary facies. It is inferred that the southeastern Hubei-northern Jiangxi area was a part of the Lower Yangtze sea area during Early Triassic, and a northward open shelf sea which might be linked with the Qinling-Dabieshan sea area in the early stage of Early Triassic. The deposits here are dominated by the deep-water basin facies and shelf facies muddy shales and limestones intercalated with calcirudite of storm origin and elastic limestones of gravity-flow origin. In the middle stage, the Dabieshan and Jiulingshan palaeocontinents were uplifted and became a restricted basin in which tidal flats, lagoons, barrier mounds and oolitic shoals were developed. Till the late stage, the periodic sea-level changes resulted in the formation of the evaporite deposits in restricted shallow-water basin and mudstones and gravity-flow deposits in deep-water basins. These changes coincide with the global sea-level curves proposed by Haq et al.(1988).