Left High and Dry: Marine Regression and Some Sundry Causes
Throughout geological history many areas of the modern terrestrial realm were inundated by shallow epicontinental seas. The term refers to their occurrence upon the continental shelves and platforms rather than in deep ocean basins. Epicontinental seas reached depths of only 1,500 to 2,000 feet, very shallow relative to most large modern marine bodies. Compared to the geological past, epicontinental seas are almost nonexistent today. Hudson Bay is the chief exception in North America. During the Late Cretaceous large areas of modern continents were submerged under warm, shallow epicontinental seas. Only recently has it become clear just how dramatic the loss of these seas was leading up to the K/T boundary.
Since the acceptance that continents are and have been on the move, atlases have been produced showing hypothesized continental positions through time (e.g, Smith et al. 1981). Knowledge of past continental positions was a boon to biologists and paleontologists who wished to make sense of animal and plant distributions. The older atlases, however, paid little attention to the presence and distribution of shallow seas. A group of British earth scientists ( Smith et al. 1994) recently published a fascinating atlas showing not only the positions of continents in the past but also their coastlines (including epicontinental seas). The maps are sequenced at about eight million year inter