JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 99, NO. B6, PAGES 12,175-12,190, JUNE 10, 1994 Climatic, eustatic, and tectonic controls on Quaternary deposits and !andforms, Red Sea coast, Egypt Raymond Arvidson, 1 Richard Becker, 1 Amy Shanabrook, 1 Wei Luo, 1 Neil Smrchio, 2 Mohamed Sultan, 1 Zakaria Lotfy, 3 Abdel Moneim Mahmood, 3 Zeinhom El Alfy 4 Abstract. Thedegree to which local c!imatic variations, eustatic sea level fluctuations, and tec- tonic uplift have influe• the development of Quaternary marine and fluvial landforms and de- posits along the Red Sea coast, Eastern Desert, Egypt was investigated using acombination of remote sensing and field data, age determinations ofcorals, and numerical simulations. False color composites generated from Landsat Thematic Mapper and SPOT image data, digital eleva- tion models derived from stereophotogrammetfic analysis of SPOT data, and fieldobservations document thata ~10-km-wide swath inland fromthecoast is covered in many places withcoalesc- ing alluvial fans of Quaternary age. Wadis cutting through the fans exhibit several pairs of fluvial terraces, and wadi walls expose alluvium interbedded with coralline limestone deposits. Further, three distinct coral terraces are evident along the coasfiine. Climatic, eustatic, and tectonic uplift controls onthe overall system were simulated using a cellular automata algorithm with the follow- ing characteristics' (1) uplift as a function of position and time, as defined by the elevations and ages ofcorals; (2) climatic variations driven byinsolation changes associated with Milankovitch cycles; (3) sea level fluctuations based on Ufrh ages of coral terraces and eustatic data; and (4) parameterized fluvial erosion and deposition. Results imply that the fans and coralline limestones were generatexi in a setting in which the tectonic uplift rate de/zreased over the Quaternary tonegli- gible values atpresent. Coralline limestones formed during eustatic highstands when alluvium was trapped upstream and wadis filled with debris. During lowstands, wadis cut into sediment• deposits; coupled wi.th continuing uplift, fans were dissectexi, leaving remnant surfaces, and wadi- related terraces were generated by down cutting. Onlylandforms from the past three tofour eus- tatic sea level cycles (i,e., -300 to400kyr)are likely tohave survived erosion and deposition associated with fluvial processes. Introduction Emerged Red Sea coastal deposits in the Eastern Desert of Egypt extend fromthemodem corm reefs to approximately 10km inland to the contact withexposures of Precambrian rocks that are part of theNubian Shield [Veeh and Giegengack, 1970; Issawi et al., 1971; Butzer, 1976; Greene, 1984; Said, 1990; Luo, 1992; S. E1Akkads andA. Dardir, unpublished map,1965](Figure 1). The overall tectonic setting is oneof uplift associated with Red Sea rifting processes [e.g., $teckler, 1985; Buck, 1986; Gar- funkel, 1988]. A number of normal faults run parallel to the coast- line, with downdropped blocks on the seaward fidesof thefaults [$abet et al., 1973a,b; 1976; Greene, 1984]. The coastal plain de- posits consist of Miocene to Holocene limestones, evaporite de- 1McDonnell Ce, nter for the Space Sciences, Deparlment of Earth andPlanetary Sciences, Washington Universi•, St. Louis, Missouri. 2Argonne National Laboratory, Argonne, Illinois 3Ain Shams Universits,, Cairo, Egypt. 4Egyptian Geological Survey and Mining Authori•, Cairo, Egypt. Copyfight 1994 bythe American Geophysical Union. Paper number 94JB00037. 0148-0227/94/94IB-00037$05.00 posits, andalluvium derived fromPrecambrian exposures [e.g., Greene, 1984]. Several discrete corm terraces are also evident along thecoastline, anda modern coral reefexists in regions that do notreceive a highflux of wadi sediment. Coastal landforms anddeposits between the towns of Quseir and Marsa Alam (Figure 1) were the focusof our work in the 1991-1992 and 1992-1993 field seasons. The features of interest were (1) alluvial fans withrelict surfaces, (2) throughgoing fluvial channels (wadis) and associated terraces; and (3) uplifted coral ter- races near the current shoreline. Both relict fan and terrace sur- faces werefoundto be covered by desert pavements. Further, ex- amination of wadi walls showed several areas where alluvium is interbedded with corMline limestones, at elevations up to -120 m above the current sea level. The alluvium and coralline limestones areof Quaternary age, given thatthese units aresuperimposed on sedimen• deposits of Miocene to latePliocene age. In thispaper we quantify thenature and origin of theQuater- naryfluvial andmarine deposits andlandforms in the study area. We determine geologic relationships between themarine and allu- vim deposits, provide age constraints fromU/Th dating of corals, and consider the overallsystem based on a cellular automata ap- proach to modeling climatic, eustatic sea level,andtectonic uplift controls on fluvial erosion and deposition.The geology of the landforms anddeposits is described first. Coralages arethen dis- cussed, along with other constraints on theevolution of thefluviM and marinedeposits and landforms. Next, a cellularauto, nata model is presented, and implications arediscussed asto theextent to which climatic fluctuations, eustatic sea level variations, and 12,175