Reefal sediments

Abstract

The processes, agents/controls, and products of sediments of coral reefs have been summarized by Orme (1977). Whether it is the Great Barrier Reef, the Belize Reef, the Florida Reef, the Bahamas Reef, the mid-ocean atolls, the fringing reefs of New Caledonia, Indonesia, Hawaii, and so on, the same patterns of sediment production, sediment transportation, and sediment deposition apply (see Gishler, 1994; Gishler and Hudson, 2004). Irrespective of the different reef organisms that contribute to the source of the sediments, namely coral, coralline algae, Halimeda, foraminiferans, mollusks, etc., the textural types of sediments are very similar in the reef slope, reef crest, reef flat, sand blanket, sand wedge, lagoon, or back reef of the different reef provinces. This reflects the similarity of the physical processes operating in the different environments and the different energy regimes which characterize the environments (Clack and Mountjoy, 1977; Stoddart, 1969). The presence or absence of aragonite and/or Mg-calcite precipitates is a more vexing issue. Inorganic precipitation has not been conclusively demonstrated in the Great Barrier Reef, but it has been reported in the Belize Barrier Reef lagoon. In the instances where muds have been reported, their origin remains equivocal (Bathurst, 1975). The same can be said for the origins of “whitings,” the possible spontaneous precipitates of aragonite, reported from the Bahamas and Persian Gulf. This issue requires further investigation.