THE PARADOX OF DROWNED CARBONATE PLATFORMS AND THE ORIGIN OF CRETACEOUS PACIFIC GUYOTS

Geochemical, stratigraphic and palaeolatitudinal data from deep boreho les drilled through Pacific guyots-flat-topped seamounts-help to expla in the drowning of these Cretaceous shallow-water carbonate platforms that once thrived through the accumulation of biogenic and inorganic c alcium carbonate sediment in mind-oceanic regions. The platforms drown ed sequentially over a 60-million-year interval while they were being transported northward by Pacific plate motion through a narrow equator ial zone (similar to 0-10 degrees S). Such platforms were apparently r esistant to the effects of Cretaceous oceanic anoxic events. Although the mechanism responsible for drowning remains unknown, the tropics ha ve not always been the refuge for atolls that they are today.