THE RECORD OF SPRINGS AT DK ARCHEOLOGICAL SITE, OLDUVAI GORGE, TANZANIA
The archaeological site occurs within a dry interval. It is at the base of the section immediately overlying the basalt. A freshwater carbonate deposit (δ13C -5.49‰; δ18O -4.60‰) occurs on top of the basalt and is 50 m west of the DK site, but in the same stratigraphic horizon. The water appears to have discharged from a fracture (or fault) at DK. This spring system was long lived as it was the source of water for a second freshwater carbonate higher in the DK section. The upper carbonate (δ13C -4.34‰; δ18O -5.06‰) also occurs during a dry interval. It is a bedded limestone (lime-mud with fossils such as ostrocods, gastropods, and oogonia) deposited from carbonate-rich groundwater. Carbonates occur only during the declining limb (wet to dry portion) of the precession cycle. In summary, the site, situated on a low gradient, distal portion of a volcanic alluvial fan was spring-fed. The groundwater discharge flowed from a fracture created localized ponded water that was a potential freshwater resource for hominins and other vertebrates during dry intervals.