Jurassic and cretaceous marine connections between the Southeast Pacific and Tethys
Abstract The affinities of the ammonoid faunas from central-west and southern South America are used to analyze the evolution of seaways and oceanic connections with Tethys during the Jurassic and Cretaceous. During the Early and Middle Jurassic, marine connection with eastern Tethys was around the Australian margin of Gondwana. From the Pliensbachian onwards, connection with western Tethys occurred through the sporadically opened “Hispanic Corridor” in Central America. In Late Jurassic time, the break-up of Gondwanaland was initiated and a seaway began to open between South America-Africa and Antarctica. Connection of the eastern Pacific with Tethyan waters through southern Africa was sporadic and was still mainly around Australia and along the now open Central American seaway. Throughout the Early Cretaceous, the opening of the South Atlantic proceeded from south to north, and the first marine connection between the southern and northern Atlantic took place in Albian time. A definite marine connection between the opened South Atlantic and eastern Tethys, with faunal migration routes, was established in Late Hauterivian-Barremian time and became fully open in the Aptian-Albian. Successive stages in the opening of a South African seaway between Tethys and the southeast Pacific show an asymmetric development to the west and east of South Africa. During Late Cretaceous time oceanic circulation continued between the South Atlantic and eastern Tethys, and true oceanic conditions developed between the southern and northern Atlantic. The Antarctic Peninsula was still located in a position adjacent to South America, preventing open circulation between the South Atlantic and Pacific oceans.