Dispersion and deposition of terrigenous sediment on continental terraces

Each continent is flanked by a continental terrace, divisible into a continental shelf, a continental slope and, in many areas, a coastal plain. Terrigenous sediments entering the ocean are fractionated into two major components: sand is shaped by longshore currents into linear bodies within a few kilometres of the shore; mud is deposited as blankets down‐current outside the sand. Continental terraces and their sediments result from the interplay of various factors, namely, rate of sediment supply, intensity of oceanographical processes, rate of subsidence or uplift, influence of tectonics, and the effect of Quaternary sea‐level changes. In the northwestern Gulf of Mexico, deposition is dominated by supply near the shore, and by the effect of sea‐level changes elsewhere. On the Orinoco‐Trinidad Shelf, sediment is deposited only where protection is provided against the swell and currents. The Sahul Shelf has a very low supply of terrigenous sediment, and relict sediments of the Holocene transgression (mainly carbonates) are widespread.The internal structure of many continental terraces, revealed by continuous acoustic reflection profiling, shows that the continental terraces existed in the past and are not merely the results of the special conditions that prevailed during the Quaternary.