Abstract

Gourma Basin was an east-west intracratonic feature that opened eastward into an ocean. Southern edge preserves facies belts representing land to deep-basin environments. Shoreward facies consist of tidal belts of microbially laminated dolomites or porostromata dolomites interstratified with clastic carbonates of local origin. Supratidal facies of finely laminated sedimentary rocks with desiccation features but no evaporites. Periodic emersion resulted in a complex succession of paleosols. Offshore are lagoon-facies rocks protected by a framework of stromatolite bioherms with detrital dolomites, indicating a high-energy environment. Slope facies of ribbon limestones with some graded beds. Synsedimentary slumping indicates a significant slope. Sporadically interstratified are muds from the platform deposits, polygenic breccias, conglomerates of ribbon limestone intraclasts, and oolitic calcarenites. Shelf-facies rocks are dolomitized but original textures are well preserved. The ribbon limestones are not dolomitized. The distribution of facies corresponds with ideal models of Wilson (1975). Comparisons with present-day facies distributions are less satisfactory, considering the dominance of cyanobacteria for which there is no modern-day counterpart. Comparisons with the modern environment suggest a subtropical semi-arid climate.--Modified journal abstract.

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