DRONES AND 3D MODELING OF THE KATBERG FORMATION IN A CLASSICAL PERMIAN—TRIASSIC BOUNDARY SITE

The Katberg Formation in the Free State, South Africa, is a sandstone-rich interval characterizing, in part, the Lystrosaurus Assemblage Zone. These sandstone bodies have been interpreted as braided (anabranching) river channels. In contrast, the fluvial systems of the underlying Daptocephalus AZ are characterized as meandering. This change in fluvial style is believed to represent the landscape’s response to rapid climatic change, from seasonally wet to seasonally dry during the latest Permian. Katberg sandstone bodies are reported as thin and wide, and considered as a stereotypical anabranching braided system. However, the upper, informally described, Swartberg Member is a thicker sandstone exposure restricted to high cliff faces and capping regional buttes. Steep gradients and high elevations limit access to these outcrops and prevent detailed architectural analysis, leaving its characterization in limbo. Drone technology allows easy access to these cliff faces and provides insight into the architectural elements and geometries of the Swartberg sandstone. In combination with photogrammetry, photomosaics and 3D models have been constructed in the current study to characterize this interval.

A comprehensive model of the Swartberg Member is constructed to understand the architectural elements at the classic Bethulie locality. The 3^d model depicts ~500 m of lateral facies relationships and is 45 m in height, enabling characterization of the Swartberg Member using Miall’s architectural element analysis. Here, the sandstone bodies represent at least three composite channel bodies that either are separated by mudstone units or are amalgamated into one, thick interval. Five architectural elements are identified including: lateral accretion deposits (LA), sandy bedforms (SB), laminated sandstone and mudstone (LS), foreset macroforms (FM), and sediment gravity flows (SG). A comparison of these features with fluvial models suggests that these channel bodies are more consistent with meandering systems than typical braided systems.