Abstract

Seismic reflection and refraction data from about 750,000 km of traverse in the Atlantic Ocean are used to construct a sediment isopach map. Sediment distribution is found to be locally and regionally complex but is largely controlled by sea-floor spreading and proximity to continental sources, although other factors (for example, CaCO3 compensation level) are important. The thinnest sediments are confined to the axial zone of the mid-Atlantic ridge primarily because of the youth of this region. Sediments progressively thicken down the flanks and into the basins—a pattern in accord with sea-floor spreading theories. Considerable regional variation is observed in the distribution of sediments. Average sediment thickness is about 1.0 km for the North Atlantic and about 0.7 km for the South Atlantic, a difference fundamentally attributed to the relative youth of the southern basin. Sediment thickness in the eastern basins is roughly 65 percent of that in the western basins and is largely the result of differences in oceanic circulation, glaciation, and continental drainage patterns. Large areas of thin sediments (<100 m) centered on the ridge crest are found in temperate latitudes in both hemispheres. These can be roughly correlated with present-day areas of low biological productivity which apparently have prevailed for a considerable period of time. Most (≈73 percent) of the sediments are found along continental margins, a region accounting for only 29 percent of the area of study.

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