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Controls on the Temporal and Spatial Variability of Carbonate Platform Architectures: A Case Study from the Nanpanjiang Basin, South China


Carbonate platform architectures are influenced by the physical, chemical, and biological conditions of the ocean. The relationship between depositional environments and the morphology of carbonate buildups provides the potential to interpret ancient marine conditions and to create predictive models of geometries and facies distributions in subsurface platforms with hydrocarbon reservoir potential. However, the relative influences of various controls on carbonate platform development are poorly constrained, in part because of the complex interaction of mechanisms that vary widely across geographic space and time. In this study, we used a Late Permian to Late Triassic isolated carbonate platform, the Great Bank of Guizhou (GBG), as a case study to evaluate controls on platform development. Sediment production on the GBG spanned the tumultuous transition from Paleozoic to Mesozoic oceans and is recorded by exceptional exposures in three geographic sectors, providing a rare opportunity to comparatively analyze spatial and temporal variability across multiple depositional systems during a period of significant global change. Our integrated analysis of satellite imagery, field mapping, chemostratigraphy, and petrography shows that physical controls such as antecedent topography and external sediment supply produced spatial variability in the platform architecture by providing structural support for the development of prograding, accretionary margins. In contrast, the lack of structural support led to over-steepening of the margin, the development of extreme relief above the basin floor, and large-scale sector collapse of destabilized erosional escarpments. Our findings further show that chemical and biological controls associated with end-Paleozoic environmental disturbance, extinction, and biotic recovery of platform-margin reefs created temporal variability in the platform architecture by shifting the dominant sites of sediment production and stabilization. Our study provides causal links between depositional environments and resulting architectures that help to refine the current understanding of controls on carbonate platform development.