Seauence-Palaeoaeographv And Coal Accumulation Regularities Of The Late Permian In Southern China

Based on outcrops, borehole and well logging data, a series of research workincluding sedimentology, sequence stratigraphy and coal accumulation of LatePermian coal-bearing formations in southern China is performed. During the study,5basic types of lithofacies are identified in the study area, which are subdivied into25types of lithofacies, and12types of sedimentary environments are identified. Amongthe identified sedimentary environments, the swamps developed from theinterdistributary bay of the delta plain, and tidal flat are the most advantageouscoal-forming environments. The regional unconformities and erosion surfaces ofincised valley sandstone base are identified as sequence boundaries which divide theLate Permian formation into3third-order sequences.Then, isochronous stratigraphicframework is established.The development characteristics of total thickness of coalseams are analyzed in different system tracts of stratigraphic framework, whichconclude that the thickest coal seams are developed in transgressive system tractwhile the lowstand system tract is identified as the most unfavourable coal-forminglocation.The coal-forming influence factors are identified for the study area. Thepaper proposes an unified model of coal accumulation. The interaction among eustasy,accommodation variation, depositional environment evolution, and coal accumulationare taken in to consideration in the unified model.