A case study of microbial mat-related features in coastal epeiric sandstones from the Paleoproterozoic Pretoria Group (Transvaal Supergroup, Kaapvaal craton, South Africa); The effect of preservation (reflecting sequence stratigraphic models) on the relat

The Magaliesberg Formation sandstones within the upper part of the Pretoria Group are interpreted as a second-order highstand systems tract within an overall clastic epeiric marine setting, where episodic braided fluvial systems fed sediment directly into a tidally dominated coastline setting. Mat-related features are abundantly preserved within the inferred tidal flat and supratidal deposits. The Daspoort Formation sandstones at a lower stratigraphic level are ascribed to a closely analogous paleoenvironmental setting, yet have hardly any preserved mat features at all; they are ascribed to a second-order transgressive systems tract in a sequence stratigraphic framework. During highstand the depositional systems are inferred to have aggraded, thus preserving the mat-related features formed in Magaliesberg intertidal–supratidal environments. During second-order transgression, the formation of the wave/tidal ravinement surface in the subtidal/intertidal environments largely obliterated the features of the Daspoort intertidal and supratidal environments, leading to a paucity of mat-related structures in the preserved Daspoort succession. This case study thus supports the application of mat-related features to integrated paleoenvironmental and sequence stratigraphic analysis, while emphasizing the role of preservation.

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► Negates simplistic links of microbial mats with clastic paleoenvironments .
► Stresses integration of sequence stratigraphy into genetic mat models.
► Case study of sequence tracts, preservability of Paleoproterozoic mat features.