DINOFLAGELLATE CYST ZONATION FOR THE MIDDLE TO UPPER EOCENE IN THE AUSTRAL BASIN, SOUTHWESTERN ATLANTIC OCEAN - IMPLICATIONS FOR REGIONAL AND GLOBAL CORRELATION

MARTIN E. RODRIGUEZ RAISING; G.RAQUEL GUERSTEIN; ALPERÍN, M.I.; GONZÁLEZ ESTEBENET, M.S., GUERSTEIN, G.R., ESPINOSA, M. Y RODRIGUEZ RAISING,M.E; JUAN J. PONCE

GEOLOGICAL MAGAZINE

CAMBRIDGE UNIV PRESS

Lugar: Cambridge; Año: 2016

0016-7568

The well-exposed marine Eocene units from southwestern Patagonia, Argentina hold usefull information to reconstruct regional climate and oceanographic patterns in an area adjacent to the Drake Passage. The aim of this paper is to integrate dinoflagellate cyst data from three sections of the southwestern Austral Basin (Río Turbio Formation) to propose a zonation scheme, which can be applied to other Southwestern Atlantic Ocean sites. The assemblages of organic walled dinoflagellate cysts have been analysed in different cropping out sections and cores showing the high potential of this fossil group as biostratigraphic markers. The comparison of dinoflagellate cyst events of the upper member of Río Turbio Formation with callibrated biostratigraphic ranges in the Paleogene Southern Pacific Ocean allowed us to date and correlate these sedimentary sections. The resulting zonation consists of four dinoflagellate cyst zones labeled RTF 1 to RTF 4, between middle Lutetian to late Priabonian. As a final point, we applied dinoflagellate cyst species with importance as palaeoenvironmental markers to assess long-term climatic and oceanographic evolution for the area. This study shows that the endemic-Antarctic dinoflagellate cyst assemblage are dominant during the middle to late Eocene (RTF 1 to RTF 3), while a significant replacement of these taxa by cosmopolitan species characterizes the upper part of the upper member of the Río Turbio Formation (RTF 4). This turnover seems to be a consequence of the changes in the ocean circulation patterns forced by the deepening of the southern Atlantic gateways (the Dake Passage and the Tasman Gateway).