Sedimentology and sequence stratigraphy of the Lopingian (Late Permian) coal measures in southwestern China

The Lopingian coal measures of southwestern China were deposited within a range of facies associations spanning a spectrum of settings from fluvial to marine carbonate platform. The transitional to terrestrial coal measures are dominated by siliciclastics, but they also contain fifteen laterally extensive marine bands (limestone beds and mudstone). These bands act as marker horizons that enable correlation between fully marine and terrestrial fades. Examination of this range of facies and their sedimentology has enabled the development of a high-resolution sequence stratigraphic framework. Set against the established backdrop of second-order Lopingian transgression, sixteen fourth-order sequences and three composite sequences (third-order) are recognized. Results show that, in the composite sequences, peat accumulation in the seaward parts of the study area predominantly correlates with early transgressive sequence sets (TSS), while in more landward areas it correlates with the middle TSS to late highstand sequence sets (HSS). Differences in peat-accumulation regimes within the sequence stratigraphic framework are attributed to variations in subsidence and background siliciclastic input rates in different depositional settings, with these combining to produce differences in the rate of accommodation change. The preservation of coal resources in the middle to late HSS in this area was most likely related to the rise of the regional base level throughout the Lopingian. (C) 2010 Elsevier B.V. All rights reserved.