Mesozoic brachiopod migrations and the opening of the North Atlantic

Abstract

The distribution of a number of Mesozoic brachiopods indicates a migration up the eastern side of the North Atlantic starting in the early Jurassic and reaching as far north as Greenland by the beginning of Cretaceous times. The brachiopods evidently reached the new Atlantic via the Rif mountains of northern Morocco and migrated both north and south from there. Some of them came from the central High Atlas which represents a gulf open to the east but closed to the west. The western High Atlas, on the other hand, was populated by successive waves of forms from the west. Brachiopods and other distinctive forms of “Tethyan” origin clearly extended considerably farther north on the eastern side of the Atlantic than they did on the west. This probably implies an early establishment of the Gulf Stream. Some Tethyan brachiopods which did not extend to the western end of the Mediterranean are found instead to have spread via northeast Siberia to cordilleran North America.