GEOLOGIC SETTING OF THE ABDUR ARCHAEOLOGICAL SITE, SOUTHERN RED SEA COAST, ERITREA, AFRICA

Stone tools discovered within uplifted marine terraces along the southern Red Sea coast of Eritrea, near the small village of Abdur, are dated to 125+/- ka. These tools represent the earliest well-dated evidence for human occupation of coastal marine environments. The Abdur Archaeological Site (AAS) lies along the northern extension of an active section of the Danakil rift system. It is located on the Buri Peninsula along the eastern shoreline of the Gulf of Zula. Three main stratigraphic units are defined: 1. The Buri Sequence is a series of marginal marine, estuarine and fluvial sediments consisting of limestones, mudstones, sandstones and conglomerates with ash and pumice beds. Ar-Ar dating of pumice and tephras put the time of deposition from at least 0.90 +/- 0.04 to less than 0.72+/-0.01 Ma. These layers were faulted, folded and eroded prior to the deposition of the overlying Abdur Reef Limestone (ARL). A few MSA obsidian tools were found in this unit. Extensive artifacts and a hominid skull have been reported from similar age fluvial deposits to the south along the base of the Eritrean Escarpment. 2. The Abdur Volcanic Complex is a small basaltic shield complex that forms the highlands along the eastern part of the AAS. Basaltic lavas from this center overlie the Buri Sequence and, in turn, are overlain by the ARL. Basalt samples dated at 1.27 +/- 0.01 Ma and 0.44+/-0.02 Ma, however, indicate that the Complex has been tectonically and magmatically active prior to, during and after the deposition of the Buri Sequence. 3. The Abdur Reef Limestone consists of a basal transgressive lag deposit overlain by an extensive build-up of mollusks, echinoderms, bioclastic sands and corals up to 4m thick. It is uplifted and tilted 1-2 degrees in a seaward direction and is faulted in places. The ARL is the remnant of a shallow marine reef system deposited approximately 125,000 years ago (MIS 5e) along the margins of the Abdur volcanic highlands and across large areas to the north. Acheulian bifacial hand axes typically occur within the basal lag deposits, while MSA-type obsidian flakes and blades are found mainly in sandy nearshore and beach environments, representing a late example of the Acheulian/MSA transition and the earliest well-dated example of early human adaptation to marine food resources.