LATE HOLOCENE SEDIMENTATION IN THE COASTAL ZONE OF AQABA, JORDAN

The city of Aqaba is located at the northern end of the Gulf of Aqaba along the active Dead Sea Transform fault in Jordan. In the coastal zone of Aqaba, stratified cultural remains from Roman to Islamic age (1st – 12th Century) and geologic sediments provide evidence for a change in the depositional environment over time. Analyses of sediment composition, depositional structures, fossil content, lateral stratigraphic relationships, and available age constraining artifacts were used to construct a history of paleoenvironments of the Aqaba coastal zone during the late Holocene. Exposure of a stratigraphic section in the coastal zone revealed 2-3 meters of aeolian sand interbedded with stratified Roman-Islamic aged structures and alluvium from flood events. Several sedimentary samples were collected from below the water table, recovered from 4-5 meter deep backhoe trenches, and each contained a greenish-grey clayey layer that may be interpreted as a marine embayment. Coulter particle size analysis characterized these samples as a clayey silt, while XRD analysis determined these sediments to be a clay composed of sepiolite (ferrian), calcite, kaolinite, halite, and albite. Microfossil analysis was conducted using a wet-sieving process and various echinoid spines were identified. The uppermost layers of sand in the section are composed of broken fragments of modern shells, mica, and subangular quartz and feldspar crystals. These sand particles appear to have been worked by water only, unlike most beach sands which are typically subrounded or rounded and worked by both water and wind. In order for this potential embayment to have formed, a beach barrier must have been present. While topographic lines are normally aligned parallel to the shoreline, the topographic lines in Aqaba are significantly altered and some are aligned perpendicular to the shore. This embayment may have formed due to tectonic subsidence. Subsequent siltation of the bay may have been human-induced or the result of a regional climatic change. Further research is necessary to investigate sedimentary deposits below the water table in the coastal zone of Aqaba, Jordan, as well as the relationship of the clay horizon to tectonic activity and the antiquities of the area.