On the cenozoic oceans: Evidence of the calcium carbonate content, [formula omitted

Abstract

The present pattern of the vertical circulation of the oceans was established c. 6.2 Ma ( Ma = million years ago ). The vertical circulation in the North Atlantic was intensified at the onset of the northern glaciation c. 2.4 Ma as well as during each of the following glaciations, particularly during the last three (Elsterian, Saalian and Weichselian). The last two interglacials (Eemian and Holocene) were probably cooler than those prior to the Saalian. It is suggested that the northern glaciations resulted from the opening of the Bering Strait which started the fresh water cycle Atlantic → N. Pacific → Arctic Ocean → N. Atlantic. This inflow together with river water, created the salinity stratification in the Arctic Ocean, the prerequisite for a sea-ice cover there. The albedo change produced the temperature drop necessary to initiate glaciations. The fixture of the Greenland ice sheet, probably during the Saalian, has resulted in an intensified vertical circulation of the oceans. Prior to 6.2 Ma the Southern Ocean was the only source of deep water. At the Eocene/Oligocene transition there was a drastic change in the ocean circulation, caused by the cooling from the ice sheet which then formed over eastern Antarctica. The δ 13 C is useful for tracing the source and the paths of deep water. The δ 18O in pre-Quaternary sequences is greatly influenced by a non-constant δ 18 O of the sea water, caused by the water circulation through the oceanic crust.