Relations between Rates of Sediment Accumulation on Continental Shelves, Sea-Floor Spreading, and Eustacy Inferred from the Central North Atlantic

Abstract

Rates of sediment accumulation were derived from Upper Jurassic to Holocene stratigraphic columns encountered in seven deep wells penetrating the coastal plains and continental shelves of southeastern North America and northwestern Africa. Three intervals with relatively fast average rates (maxima) and two intervening intervals with relatively slow average rates (minima) were determined on both continental margins as follows: maximum 1, Cretaceous (136-65 m.y. B.P.); minimum 1, Paleocene (65-53.5 m.y. B.P.); maximum 2, early through middle Eocene (53.5-45 m.y. B.P.); minimum 2, late Eocene through Oligocene (45-22.5 m.y. B.P.); maximum 3, Miocene (22.5-5.5 m.y. B.P.). Each maximum lasted 10 to 70 m.y. and correlated with a worldwide epicontinental marine transgression or with the reversal between a transgression and a regression. Each minimum lasted 10 to 20 m.y. and correlated with a worldwide marine regression or with the reversal between a regression and a transgression. To a first approximation, the sedimentary maxima and minima are directly proportional to rates of sea-floor spreading in the intervening ocean basin. The successive maxima and minima in average rates of sediment accumulation on continental shelves are controlled by eustatic sea-level changes. Major eustatic changes in sea level, other than glacio-eustatic, result from changes in the cubic capacity of ocean basins primarily caused by changes in the volume of the worldwide mid-oceanic ridge system and by orogenic compression of continental crust. These two factors are related in a cycle manifested in the stratigraphic record of epicontinental marine transgression and regression: (1) Volume increase of the worldwide mid-oceanic ridge system associated with relatively fast sea-floor spreading and net orogenic quiescence of continents results in transgression. (2) Volume decrease of the worldwide mid-oceanic ridge system associated with relatively slow sea-floor spreading and net orogenic activity of continents results in regression.