A new Devonian fish fauna, and revision of post- Ordovician stratigraphy in the Ross River Syncline, Amadeus Basin, central Australia

A Devonian microvertebrate fauna from the N'Dahla Member, previously assigned to the Cambro-Ordovician Pacoota Sandstone, has led to a revision of the stratigraphy in the Ross River Syncline. The N'Dahla Member is included in the Devonian Pertnjara Group, and is correlated on faunal evidence with the Deering Siltstone Member of the Parke Siltstone in the central Amadeus Basin. The overlying sandstone, previously mapped as Mereenie Sandstone, is presumed to be equivalent to one of the overlying formations of the Pertnjara Group. The N'Dahla Member rests with angular unconformity on the underlying Pacoota Sandstone, this break possibly representing both the Rodingan and Pertnjara Movements of other authors. Evidence of the Devonian Pertnjara Movement in the Amadeus Basin is reviewed, and the possibility that the Mereenie Sandstone was never deposited in the Ross River sequence is discussed. The recognition of Mereenie Sandstone in other outcrops and wells in the eastern part of the Amadeus Basin requires reexamination. - Authors