The geology of Bunyeroo, Brachina, and Parachilna Gorges

Gordon Webb

The Adelaidean succession exposed in the Flinders Ranges provides one of the most complete sedimentary records of the late Proterozoic found anywhere on earth (Preiss, 1987). Excellent exposures of the Wilpena Group stratigraphic units of the upper Adelaidean Rift Complex are bisected by three perpendicular gorges (Bunyeroo, Brachina and Parachilna or BB&P, respectively) immediately to the northwest of Wilpena Pound. This area is referred to as the ABC Range. The stratigraphic layers exposed in the gorges dip steeply to the west. As a result, walking up these gorges from east to west provides an excellent introduction to the time-sequence geology of the upper Adelaidean Rift Complex. The following section describes the stratigraphic units that are ncountered as one travels up sequence from east to west beginning at the base of the first hills that form the lower parts of these gorges (Figure 1).