Verdel, Charles1, Donnellan, Nigel1, Normington, Verity1, Simmons, Jack1
1Northern Territory Geological Survey, Alice Springs and Darwin, Australia
Neoproterozoic stratigraphic nomenclature has historically differed between the eastern and central to western parts of the Amadeus Basin, leading to issues in basin-wide correlation and evaluation of potential lateral facies changes. In the more extensively described eastern part of the basin, the major Ediacaran lithostratigraphic units are (in ascending order) the basal Ediacaran cap carbonate of the Olympic Formation, Pertatataka Formation, Julie Formation, and latest Ediacaran lower Arumbera Sandstone. New mapping has revealed that most of these units correspond with parts of the informal and historical “Winnall beds” of the central and western Amadeus Basin. The new, formally defined Winnall Group spans Ediacaran to perhaps Cambrian time and consists of five formations: in ascending order, the Breaden, Gloaming, Froud, Liddle, and Puna Kura Kura formations. In the westernmost part of the Northern Territory Amadeus Basin (i.e., the region stretching from approximately Watarrka (Kings Canyon) National Park to the Western Australia border), the main part of the Winnall Group that is exposed is the Liddle Formation, a succession of cross-bedded sandstone that reaches a thickness of approximately 500 meters. Lithostratigraphic comparison with the eastern Amadeus Basin suggests that the Liddle Formation is partly or entirely correlative with carbonate of the Julie Formation, and extensive detrital zircon U-Pb data from the Liddle Formation are permissive of a mid to late Ediacaran age assignment. The Liddle Formation may be a stratigraphic counterpart of the late Ediacaran Bonney Sandstone in the Adelaide Superbasin of South Australia.
Charlie Verdel is a project geologist with the Northern Territory Geological Survey in Alice Springs.