Mid Cenozoic Palaeoclimatic and Palaeoceanographic trends in the Southwest Atlantic Basins, a Dinoflagellate view.

GUERSTEIN, G.R., GULER, M.V., BRINKHUIS, H AND WARNAAR, J.

The Paleontology of Gran Barranca: Evolution and Environmental Change through the Middle Cenozoic of Patagonia

Cambridge Universtiy Press

Lugar: Cambridge; Año: 2010; p. 349 - 405

ABSTRACT. Middle Eocene to Miocene organic-walled dinoflagellate cysts (dinocysts) from marine deposits in Southwest Atlantic sedimentary basins in Patagonia (Austral, Golfo San Jorge, Colorado and Punta del Este, from south to north) reveal details of the palaeoclimatic and palaeoceanographic evolution of the region. There is evidence for four transgressive events during this interval, viz, in the middle Middle Eocene, Late Eocene, Late Oligocene – earliest Miocene, and Middle to Late Miocene. The Middle Eocene dinocyst assemblages are dominated by typical high-latitude, sub-Antarctic endemic floras recorded from many different sites from around the Southern Ocean. During the Late Eocene, these endemic species became less abundant and were partially replaced by more diverse assemblages with markers of cooler, more offshore conditions and an increased number of heterotrophic Protoperidiniaceae. In contrast, the Late Oligocene and Middle Miocene assemblages are often dominated by more cosmopolitan species. Hence, material from the last two transgressive events suggest more temperate to warm surface water conditions. The trends recorded from the Southwest Atlantic basins coincide with the large-scale palaeoclimatic and palaeoceanographic trends previously proposed by other authors on the basis of analysis of sites in the Southern Ocean.