NEOPROTEROZOIC MICROFOSSILS FROM THE OFFICER BASIN, WESTERN-AUSTRALIA

Microfossil assemblages are described from the early Neoproterozoic Ma dley and Browne Formations, western Officer Basin. One chert and eleve n siliciclastic samples yielded microfossils. Myxococcoides cantabrigi ensis occurs as pustular mats in the chert sample and Eomicrocystis ma lgica, Pterospermopsimorpha granulata, Skiagia sp. cf. S. pusilla, and undetermined species of Obruchevella, Heliconema, and Trachystrichosp haera are present in acid macerated samples. Leiosphaeridia spp. and S iphonophycus spp. are also found in fine-grained siliciclastic samples , with clusters of Synsphaeridium sp. in some samples. These findings enable a more substantial reconstruction of the palaeoenvironment of S upersequence 1 in the western Centralian Superbasin. The acanthomorph acritarchs are considered to be planktonic eucaryotes washed into envi ronments which ranged from coastal sabkha through to tidal flats, whic h may be the source of the prokaryotic, benthic, matforming cyanobacte ria.