| Early Cretaceous coal measures in the Pan-Sanjiang Basin have been studied using coal-accumulation models, sedimentology, and sequence stratigraphy applied to outcrop, borehole, well log, seismic and geochemical data. Within the research area the main coal-bearing strata are the Chengzihe and Muling formations. Siltstones, fine sandstones, mudstones and coals dominate the Chengzihe Formation, while the Muling Formations is dominated by mudstones, siltstones, and fine to medium grained sandstones. Five sedimentary facies are identified:alluvial fan, braided river, meandering river, delta and lacustrine. The main coal-accumulating environment occurs at the transition between upper and lower delta plain facies. Based on the evolution of the sedimentary environment, characteristics of sequence boundaries and wavelet transformation on gamma-ray logs (GR), five sequence boundaries are recognized. These sequence boundaries include regional unconformities, erosion surfaces resulting from river incision, and reverse surfaces. The sequence boundaries have been used to subdivide the Early Cretaceous coal measures into four third-order sequences. The main coals initially formed under lowstand system tracts and early transgressive system tracts but subsequently developed under middle and late transgressive system tracts and maximum lake flooding surfaces. Sâ…¢2 is identified as the sequence most favourable to coal accumulation. Palaeogeographic lithofacies analyses indicate delta plain facies are predominant. These facies have source directions from the southwest, northwest and northeast with water invasion from the east. Collectively these data have been used to generate a coal-accumulating model for the inland fault basin and should provide a powerful tool for future coal resource exploration. Besides, reserves of shale gas and favorable exploration zones were predicted in the study area.
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