Testing applicability of models of distributive fluvial systems or trunk rivers in ephemeral systems: Reconstructing 3-D fluvial architecture in the Beaufort Group, South Africa

Multi-kilometer-scale strike and dip exposures of fluvial deposits from the Permo-Triassic Beaufort Group enable detailed analysis of spatial and temporal changes in fluvial style and stacking patterns. A study succession 145 m thick in the Abrahamskraal Formation comprises a hierarchy of channel-related deposits, from stories through channel belts that are stacked into nine channel-belt complexes in four complex sets. Channel belts show evidence for both downstream and lateral accretion and include common upper-phase plane bedding. Floodplain deposits comprise crevasse-splay sandstones and siltstone packages showing upward fining from green-gray siltstone into distinctive purple claystone, interpreted as a drying-upward trend in shallow ephemeral lakes. The lower stratigraphy is dominated by splay complexes, overlain by increasingly incised and amalgamated channelized systems with little preserved floodplain material. Paleocurrents are consistently to the northeast.