Abstract:
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 palaeoenvironmental 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 palaeoenvironmental and sequence
stratigraphic analysis, while emphasizing the role of preservation.
