. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography SUMMARY 347. 6CN 52° W FIGURE 40. Sediment distribution of the Amazon shelf. Modern terrigenous muds are deposited beneath a north-trending coastal mud stream. "Relict" muds are believed to have been deposited by the same mud stream during lower stands of sea level. From Milliman et al. (inpress). in response to coastal boundary flow, but elsewhere appears to have developed more or less spontaneously further out on the shelf surface. Curre
. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography SUMMARY 347. 6CN 52° W FIGURE 40. Sediment distribution of the Amazon shelf. Modern terrigenous muds are deposited beneath a north-trending coastal mud stream. "Relict" muds are believed to have been deposited by the same mud stream during lower stands of sea level. From Milliman et al. (inpress). in response to coastal boundary flow, but elsewhere appears to have developed more or less spontaneously further out on the shelf surface. Current lineations (sand ribbons and erosional furrows) are abundant. Coarse sand lags occur on highs, finer sands occur on their downcurrent slopes and in adjacent lows. The shelf around the British Isles is an example of an autochthonous shelf that has reacted in a more vigorous fashion, in response to a high-intensity tidal regime. A well-organized pattern of sand dispersal consists of sand streams that extend from bed load partings to bed load convergences, or to the shelf edge. Nearshore morphologic elements have largely been obliterated. However, well-defined fields of tide-maintained sand ridges are probably analogous to the shoal retreat massifs of the Middle Atlantic Bight. Allochthonous shelves occur adjacent to large rivers with sediment loads sufficiently large to locally slow or reverse the sense of the postglacial transgression. Trans- port is dominantly by water column advection (mud streams) but diffusion in response to bottom wave surge is important. Allochthonous deposits of fine sand and mud are commonly not continuous, but tend to leave "windows" in which autochthonous sands are exposed, Such windows are not necessarily transient phenomena, but may reflect areas in which the concentration of suspended sediment in the bottom nepheloid layer is counteracted by a relatively high level of "hydraulic ; Textural gradients in autochthonous
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