This study of stratigraphy, chronology and sedimentology at Lake Amadeus, a major playa lake in central Australia, provides for the first time a Late Tertiary and Quaternary sedimentary sequence from the continent's centre. The Cenozoic sediments of the lake basin consist of two major units: the Uluru Clay; and the overlying Winmatti Beds. At least 60 m of Uluru Clay overlies Proterozoic dolomitic limestone and consists of uniform clay horizons with minor intercalated gypsum. The clay was deposited in a shallow lacustrine and fluvial environment. Conditions were periodically saline and frequently dry. The basal Uluru Clay is estimated to be over 5 Ma old.