Bedrock outcrops were mapped at 61 sites spread over 7550 square km of the Great Victoria Desert, including many that had previously been geologically mis-interpreted, or had never before been visited. The sedimentary depositional environment of the Observatory Hill Beds is confirmed as in alkaline playa lakes. The disconformably overlying Wanna Beds result from infilling of the original lakes(s) by fluvial sands after renewed tectonic movement. Drilling was recommended to test for trona mineralization. Observatory Hill Beds outcrops were observed in the Wallatinna area. Contrary to the published 1:250 000 sheet information, some steeply dipping, tightly folded, probable younger Adelaidean sandstones were seen to outcrop.