Chapter 3 Case Histories of Coexisting Reefs and Terrigenous Sediments: The Gulf of Elat (Red Sea), Java Sea, and Neogene Basin of the Negev, Israel

Abstract

Abstract The contemporaneous deposition of clastics and development of carbonate-secreting organisms, once thought to have been mutually exclusive, is actually quite common through a variety of sedimentological and biological processes. In the Gulf of Elat (Red Sea), the hot, dry climate, and infrequent rain-fall result in flash-flooding. Coarse sands, washed down from the adjacent highlands through intermittant streams (wadis), are deposited in alluvial-fan complexes while reef complexes contemporaneously are deposited along the shelf break. The carbonate-secreting organisms overcome the inhibiting effects of the clastic material due to sediment coarseness and the long periods of quiesence between flash-floods. Reef complexes almost fringe the entire Gulf of Elat coastline. The humid climate of the Java Sea, contrary to the Gulf of Elat, ensures a consistently heavy, sediment-ladened run-off from the islands composed primarily of fine-grained material. Longshore currents redistribute these sediments laterally, away from the carbonate-secreting organisms allowing reef development in clear water approximately 25 km from the Java coast. Within the Hazeva Formation in the Neogene Yeroham Basin in Southern Israel, terrigenous and carbonate facies are mixed in an upward-coarsening clastic sequence topped by an erosion-resistant oyster bank (Crassostreids). By analogy with modern environments, the oyster bank is considered to be intertidal in origin. Probably as a paleoecological retreat into a setting where predators cannot survive, oysters have adapted to a muddy environment by eliminating clay-mucous particles as pseudo-feces. Here, the mutually exclusive relationship between fine-grained terrigenous sediments and carbonate-secreting organisms is not the case.