WARM SALINE BOTTOM WATER IN THE ANCIENT OCEAN

Considerable isotopic evidence [oxygen isotopic paleotemperature studies on benthic foraminifera from deep-sea cores] indicates that oceanic bottom water was much warmer in the geological past. A simple convection model driven by multiple turbulent buoyant plumes and observations of present deep water formation have led to the development of a theory for the formation of warm saline bottom water. Changes in the size and configuration of marginal seas in net evaporation zones due to lithospheric plate motions and eustatic sea level change probably caused these seas to become sources of warm saline bottom water. Evidence from the paleotemperature record and paleogeography during the Late Cretaceous is used to reinforce the hypothesis. Climatic and chemical consequences of the formation of warm saline bottom water are discussed.