A system of parallel arcuate ridges dominates the present‐day topography of the Billa Kalina area, South Australia; facies relationships indicate that they are silicified strandlines of a Miocene lake, etched out by later erosion. Clays and dolomites of the Miocene Mirikata Formation (Billa Kalina Clay and Millers Creek Dolomite Members) were deposited in the distal portion of the lake, which at its peak was over 100 km wide.