CLIMATIC, EUSTATIC, AND TECTONIC CONTROLS ON QUATERNARY DEPOSITS AND LANDFORMS, RED-SEA COAST, EGYPT

The degree to which local climatic variations, eustatic sea level fluc tuations, and tectonic uplift have influenced the development of Quate rnary marine and fluvial landforms and deposits along the Red Sea coas t, Eastern Desert, Egypt was investigated using a combination of remot e sensing and field data, age determinations of corals, and numerical simulations. False color composites generated from Landsat Thematic Ma pper and SPOT image data, digital elevation models derived from stereo photogrammetric analysis of SPOT data, and field observations document that a approximately 10-km-wide swath inland from the coast is covere d in many places with coalescing alluvial fans of Quaternary age. Wadi s cutting through the fans exhibit several pairs of fluvial terraces, and wadi walls expose alluvium interbedded with coralline limestone de posits. three distinct coral terrace are evident along the coastline. Climatic, eustatic, and tectonic uplift controls on the overall system were simulated using a cellular automata algorithm with die following characteristics: (1) uplift as a function of position and time, as de fined by the elevations and ages of corals; (2) climatic variations dr iven by insolation changes associated with Milankovitch cycles; (3) se a level fluctuations based on U/rh ages of coral terraces and eustatic data; and (4) parameterized fluvial erosion and deposition. Results i mply that the fans and coralline limestones were generated in a settin g in which the tectonic uplift rate decreased over the Quaternary to n egligible values at present. Coralline limestones formed during eustat ic highstands when alluvium was trapped upstream and wadis filled with debris. During lowstands, wadis cut into sedimentary deposits; couple d with continuing uplift, fans were dissected, leaving remnant surface s, and wadirelated terraces were generated by down cutting. Only landf orms from the past three to four eustatic sea level cycles (i.e., appr oximately 300 to 400 kyr) are likely to have survived erosion and depo sition associated with fluvial processes.