CARBONATES AT ARCHAEOLOGICAL SITES AND ENVIRONMENTS PROXIMATE TO THE NILE RIVER DURING THE EARLY TO MID HOLOCENE IN CENTRAL AND NORTHERN SUDAN

The African Humid Period is the latest in a series of Saharan pluvial periods studied using carbonates. Evidence from desert paleolakes indicate regionally higher groundwater which discharged at the surface creating a wetter environment beyond what the increased seasonal precipitation could support alone. Carbonate cemented material and sediments have been noted at key archaeological sites such as Khartoum Hospital, al-Khiday, and site distributions along Wadi Howar. Carbonate morphology and oxygen isotope composition is used to develop a conceptual model for its accumulation in areas near the Nile River. Morphological evidence shows a variety of formative environments including both saturated and unsaturated conditions at key topographic locations indicating water availability above modeled contemporary Nile River flood extents. Isotopic results show locations dominated by evaporative enrichment at higher elevations with a transition to stable isotopic conditions at lower elevations. For areas beyond the range of a Nile inundation or an associated river fed alluvial aquifer, the only perennial moisture source capable of maintaining an isotopic equilibrium would be groundwater. Results coincide with isotopic patterns observed in paleolake carbonates, and published water values for fossil groundwater in the Nubian Sandstone Aquifer. This model provides an explanation for the accumulation of carbonates at archaeological sites, while offering greater understanding of contemporary water availability for vegetation, animals, and human populations, and whether the Nile River functioned as the dominant water source, as it did for later agricultural populations.