Early Cretaceous (Neocomian) microplankton from the Carpentaria Basin,northern Queensland

The Neocomian upper Helby Beds, basal Rolling Downs Group and Gilbert River Formation of the Carpentaria Basin contain a dinoflagellate sequence divisible into three zonal intervals; the zones represent the oldest continuous marine Cretaceous record for eastern Australia. Zone DK1 (dated latest Jurassic to Berriasian) commences with the first appearance of four species, zone DK2 (dated Valanginian) with that of four or five species, and zone DK3 (dated Hauterivian to Barremian) with that of three species.

Biostratigraphic aspects are discussed of species selected as possible zone marker fossils in so far as they (a) are relatively poorly known, or represent new species, and (b) have no previously published Neocomian record. New combinations are proposed of one acritarch species and six dinoflagellate species. One new acritarch genus and species, Pseudofromea collaris, and four new dinoflagellate species — Canningia crassicingulata, Cleistosphaeridium australe, Cyclonephelium asymmetricum, and Muderongia testudinaria — are proposed and described.