Geologic Background of Outcrop Analogue

The Triassic Beaufort Group of South Africa

Simplified geological map of South Africa
Figure 1: Simplified geological map of South Africa, showing the different componants of the Karoo Supergroup. The study area is highlighted.

The Karoo Supergroup of the Karoo Basin, South Africa (Figs 1, 2), comprises a complete Permo-Triassic basin-fill succession of deepwater, through deltaic to fluvial and aeolian deposits (Figs 1,2). The Beaufort Group is the Triassic fluvial section. It includes 5000 m of both low and high net:gross fluvial deposits of both braided and meandering styles, associated with semi-arid floodplain material (Fig 2). Sections of the Beaufort contain fossils of early reptiles (Dicynodonts), which provide a partial biostratigraphic control. Volcanic ash beds may also provide an opportunity for radiometric dating for better control on rates of deposition, as recently achieved for the underlying deepwater succession (Fildani et al., 2007).Exposures are excellent in selected areas, mainly in river valleys but also include roadcuts.

The suitability of the Beaufort Group outcrops are enhanced by the fact that they are a similar age, deposited in a similar palaeolatitude and palaeoclimatic setting, and are a comparable thickness to prospective fluvial strata of the Exmouth Plateau, offshore NW Australia. The presence of cored boreholes, drilled during a time of Uranium exploration and situated close to outcrops is an added attraction for the Beaufort Group, and the S.A. Geological Survey has confirmed that the project can have access to this material.

Figure 2: Tectonostratigraphy of the Karoo Supergroup, showing the position of the Beaufort Group target sucession (boxed), from Turner (1999).
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