. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography Fig. 3. The delta terrace redrawn from Dunbar and Rodgers (1957, p. 47). Topset, foreset, and bottomset beds are shown to develop when a sediment-laden river enters a quiet body of water. Such delta terraces are common geomorphic forms; they should not be confused with the entirely hypothetical wave-built terrace. Note especially that the nick-point is at water level and not below; wave action would tend to modify or destroy the delta terrace. A ris
. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography Fig. 3. The delta terrace redrawn from Dunbar and Rodgers (1957, p. 47). Topset, foreset, and bottomset beds are shown to develop when a sediment-laden river enters a quiet body of water. Such delta terraces are common geomorphic forms; they should not be confused with the entirely hypothetical wave-built terrace. Note especially that the nick-point is at water level and not below; wave action would tend to modify or destroy the delta terrace. A rising water level would drown it, producing a feature which might erroneously be interpreted as a wave-built terrace. the shore. Under extreme storm conditions, the outer limit may sometimes reach 20 meters. Strictly speaking, this should be called "surf base" or "surge base" as it is related to surf action rather than the depth of stirring by open-sea waves (Dietz, 1963). As Moore and Curray (1964) have pointed out, there is really a zone of wave base, effective for various sedimentary grades, shallow for boulders and gravel, deeper for silt and clay, that is activated in cycles up to a century or so. Historically, there has been much confusion about the lower limit of wave base and marine abrasion. The traditional tendency was to relate the depth of the shelf edge, which is normally situated at about 100-200 meters, to the bottom friction of open-sea waves (see Fig. 1). One may certainly speak of a "feeling the bottom" by open sea waves, but this is unimportant as compared to the surf action, especially over long periods when it is combined with the large Quaternary oscil- lations of sea level. Several authors have remarked on the widespread evidence of late Pleistocene shore lines and undisturbed relic sediments on the outer shelf. Evidently this means that since the time that sea level has been at its approximate (modern) level (a matter of about
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