Continental Positions

Figure 3: The continental positions during the Late Cretaceous.(Lucas, 1994)

Continental rifting and the growth of new oceans resulted in greatly extended midocean ridges. As the ridges grew and reduced the volume of the ocean basins, there was a eustatic rise in sea level, resulting in widespread marine transgressions in the Cretaceous. In North America, the sea at maximum transgression extended as an epicontinental sea called the Interior Seaway all the way from the Arctic Ocean to the Gulf of Mexico, dividing North America into two islands. Gondwana fragmented and the Atlantic Ocean basin began to form. The Cretaceous was a time of major mountain building, when the North American cordillera and the South American Andes formed. The varied landforms that existed at this time (oceans, epeiric seas, mountains) enabled organisms to diverge and inhabit new niches.(Lucas, 1994)