Dinoflagellate cyst paleobiogeography during the Middle Eocene in southern Southwest Atlantic Ocean

M. SOL GONZÁLEZ ESTEBENET; G. RAQUEL GUERSTEIN; MARTA ALPERIN

Mendoza

Congreso; 4th INTERNATIONAL PALAEONTOLOGICAL CONGRESS; 2014

INTERNATIONAL PALAEONTOLOGICAL ASSOCIATION

The middle Eocene in high latitudes of the Southern Hemisphere is characterized by an Antarctic endemic assemblage of organic-walled dinoflagellate cysts. The distribution of these microfossils responds to a surface ocean circulation patterns with broad clockwise gyres surrounding Antarctica. During the Oligocene the deepening of the Tasman Gateway and the Drake Passage would have generated a circumpolar water flow responsible for the disruption of the local gyre system which caused the extinction of the endemic assemblage. Recently it has been suggested that during the middle Eocene, shallow water flows developed through incipient openings of the Tasman Gateway. As for the Drake Passage, the time for its opening and deepening is still being discussed, with ages ranging from the middle Eocene to the early Miocene. Recently some authors proposed an early opening for this passage, with tectonic and oceanic characteristics similar to those proposed for the Tasmania Gateway. In this work we compared the middle Eocene dinoflagellate cysts in the Drake area using multivariate analysis. The results show two clusters: one cluster comprises the localities to the north of the passage, from the Austral Basin, and the other cluster includes the localities to the south of the passage at the Peninsula Antarctica and Scotia Sea. In this way, our results allow us to determine a latitudinal dinoflagellate cyst differentiation that could be related to an early development of shallow water flows through the Drake Passage during the middle Eocene.