A new early Paleocene dinoflagellate cyst species,Trithyrodinium partridgei: its biostratigraphic significance and palaeoecology

A palynological investigation of lower Paleocene (lower Teurian) marine sediments of the Abbotsford Formation, exposed in the Fairfield Quarry, Dunedin, New Zealand, reveals a well-preserved association of dinoflagellate cysts and miospores. Thirty-six dinoflagellate species representing 26 genera were recorded, including one new peridinioid dinoflagellate species, Trithyrodinium partridgei characterized by a three-layered wall and a distinct brown, foveolate mesophragm. Trithyrodinium partridgei has a narrow range and at Fairfield Quarry co-occurs with typical New Zealand late Danian to Selandian index species such as Glaphyrocysta perforata and Alterbidinium pentaradiatum; hence it may prove an additional useful stratigraphic marker. The terrestrial palynomorph assemblage from samples within the range of Trithyrodinium partridgei includes 36 spore-pollen species dominated by the podocarp pollen Phyllocladidites mawsonii. The presence of Nothofagidites waipawaensis and Tricolpites phillipsii confirms a Paleocene age for the assemblage. The abundance of terrestrial palynomorphs and the composition of the dinocyst assemblages suggest a marine nearshore depositional environment.