Tectonic forcings of Maastrichtian ocean-climate evolution

A global compilation of deep-sea isotopic records suggests that Maastrichti an ocean-climate evolution tvas tectonically driven. During the early Maast richtian the Atlantic intermediate-deep ocean was isolated from the Pacific , Indian, and Southern Oceans; deep water formed in the high-latitude North Atlantic and North Pacific. At the early/late Maastrichtian boundary a maj or reorganization of oceanic circulation patterns occurred, resulting in th e development of a thermohaline circulation system similar to that of the m odem oceans. A combination of isotopic and plate kinematic data suggests th at this event was triggered by the final breaching of tectonic sills in the South Atlantic and the initiation of north-south flow of intermediate and deep water in the Atlantic. The onset of Laramide tectonism during the mid Maastrichtian led to the concurrent draining of major epicontinental seaway s. Together, these events caused cooling, increased latitudinal temperature gradients, increased ventilation of the deep ocean, and affected a range o f marine biota.