Palynological evidence for the age of the synorogenic Brewer Conglomerate,Amadeus Basin,central Australia

An assemblage of spores recovered from the Undandita Member of the Brewer Conglomerate, the uppermost unit of the Pertnjara Group in the Amadeus Basin of central Australia, establishes the age of that formation as Late Devonian. Comparison with spore assemblages from sedimentary basins in Western Australia indicates that the central Australian assemblage is dateable within the post-early Frasnian to pre-late Famennian interval. Fish remains and spores previously described from the Parke Siltstone at the base of the Pertnjara Group are of probable early Frasnian age, so it now appears that the entire group was deposited during the Late Devonian. The Brewer Conglomerate is of synorogenic origin, and was deposited during uplift associated with the Alice Springs Orogeny; the spore data thus indicate that this tectonic event began in the Late Devonian. Isotopic age determinations in the Arltunga Nappe Complex and the Strangways Range of the Arunta Block have yielded Early Carboniferous dates. These possibly reflect a later stage of deformation than that which was responsible for the deformation and folding of the Brewer Conglomerate.