THE DIVISION OF THE SINIAN-TRIASSIC SECOND-ORDER SEQUENCES IN THE MIDDLE-SOUTH OF ANHUI
Du senguan(Anhui Academy of Geological Survey Hefei 230001)
The middle- south of Anhui was in the transitional environment from terrestrial clastic sedimentary environment to carbonatesedimentary environment from the Sinian to Triassic. Eight second-order stratigraphic sequences are determined based on the changes of depositional facies succession in the inner sedimentary basin or the joint zone of littoral and neritic facies with the characteristics of stratigraphic sequence interface and condensed section at key places being taken into consideration. Each second-order sequence shows a general trend of change in facies succession from shallow to deep and back to shallow at the places of inner basin or joint zone of littoral and neritic facies, coincided with the curve of sea-level fluctuation. The interfaces of second-order sequence and condensed section are always the most evident up-or-down transitional places of sea level of several third-order sequence in the second-order ones. And the interfacetypes tend to be concerned with tectonic movement, sea -level fluctuation and glacial events.