Eocene opening of Drake Passage: geological and geophysical evidence from Tierra del Fuego

GHIGLIONE, M; YAGUPSKY, D.L.; GHIDELLA, M.; RAMOS, V.A.

San Salvador de Jujuy

Congreso; XVII Congreso Geológico Argentino; 2008

Age estimates for the onset of a seaway through Drake Passage range from middle Eocene to early Miocene, complicating interpretations of the relationship between ocean circulation and Cenozoic global cooling. Here we present evidence for the presence of a Paleocene – Eocene extensional depocenter (i.e. lateral rift) located parallel to the actual continental-oceanic crust boundary in Tierra del Fuego. An accurately-dated post-rift unconformity indicates that extensional faulting ended in this area during the Eocene, in concurrence with a previously reported eightfold increase in South America – Antarctica separation rate, and the onset of oceanic basins in the incipient Drake Passage. The coincidence of these facts indicates progressive strain concentration on the zone of future crustal separation (i.e. Drake Passage) after abandonment of lateral rifts. Our findings strongly support the recently proposed middle Eocene age for the opening of small basins in the embryonic Scotia Sea and the ensuing opening of a seaway across Drake Passage at ~ 41 Ma.