Geomorphology of Shallow Water Coral Reef Environments in the Red Sea

Abstract

In this chapter, we examine the different processes that control the orientation and arrangement of shallow water coral reef environments in the Red Sea. Particular focus is paid to the diversity, distribution, and abundance of coral reefs in Saudi Arabia, where shallow water (<30 m) environments have been mapped into one of sixteen types of ‘coral reef system’. Each of these types of coral reef system represents the terminal node in a decision tree that differentiates reef environments based on distinctive planar morphology, that is, viewed from above and audited from high-resolution satellite imagery. The wide variation in morphology of the Red Sea reefs is primarily governed by the width of the coastal shelf. Coral reef systems can be described as either ‘shore-attached’ or ‘detached’ on the basis of the depth of water separating them from a landmass. The morphology of attached systems ranges from the simple arrangement of fringing reefs and sediments to more complex forms that extend into the Red Sea basin and are incised by channels, large lagoons, and repetitive reef lineaments. There is also considerable diversity in morphology in detached coral reef systems, which are as abundant overall as those that are shore-attached. Several morphological types of coral reef system are restricted to narrow regions of latitude. Such distributional trends may be explained in process terms by the rift tectonics of the Red Sea basin, spatial variability in the presence of sub-seafloor evaporites, the input of siliciclastic (non-carbonate) detritus onto the coastal shelf via wadis, and eustatic sea-level control. These processes act in concert, but at different spatial and temporal scales, to deliver diverse coral reef morphologies throughout the Red Sea basin.