The Taxonomy and Palaeobiogeography of Small Chorate Dinoflagellate Cysts from the Late Cretaceous to Quaternary of Antarctica

Small chorate dinoflagellate cysts are common in Upper Cretaceous to Quaternary sedimentary successions around the Antarctic margin. Taxonomic confusion surrounding dinoflagellate cysts and acritarchs of similar morphology throughout the southern high palaeolatitudes has hitherto limited investigation of their palaeoecological significance. This study aims to solve the taxonomic problems, and to allow a new assessment of dinoflagellate cyst acmes. A detailed morphological study of new material from the Lopez de Bertodano Formation of Seymour Island, Antarctic Peninsula, is presented. These dinoflagellate cysts are identified as Impletosphaeridium clavus Wrenn & Hart 1988 emend. nov. Their gross morphology and their vast abundances in the James Ross Basin are strongly suggestive of dinoflagellate blooms. This scenario implies similarities to modern dinoflagellate cysts from the polar regions.