T213 The History of Humans and the Hydrologic System: Exploring Relationships between Cultures, Climate, and Hydrology through Time II

Tuesday, 11 October 2011
1:30 PM - 5:30 PM
Room 101FG

SPRINGS AND THEIR “SPHERE OF INFLUENCE” ON ARCHAEOLOGICAL SITES

Paper number: T213-3
Program: Technical Sessions
Time: 2:00 PM – 2:15 PM

Authors

Abstract

The reason for the location of an archaeological site may not always be clear, despite extensive investigation of the artifacts, the geologic context and the reconstruction of the surrounding landscape. How are boundaries or the area associated with a site determined? Identification of a freshwater source associated with an archaeological site provides some insights into these uncertainties. Areas of groundwater discharge vary from discrete, singular point-sources i.e. springs or a line of springs to broad areas of more diffuse seepage, where water slowly percolates onto the surface. The water may be locally recharged or may be supplied by regional aquifers. Groundwater velocity is slow (meters/yr) and, being shielded from evaporation, is buffered against short-term changes in hydrologic budget. Consequently groundwater discharge is likely to be more dependable than surface water systems that are subject to the vagaries of local weather. Sustained groundwater discharge supports vegetation ranging from groundwater-fed forests and woodlands to wetlands that can be a source of both water and food. These lush habitats may be as large as several km2. The sediment records of groundwater discharge may contain: peat and green clay deposits that contain eolian-transported mineral matter, macrophyte plant remains (e.g. roots, stems), pollen, phytoliths, diatoms, root casts, charcoal, carbonate and manganese-rich nodules.

Four East African archaeological sites were examined with respect to archaeology, geology, geomorphology, as well as plant and animal remains. These sites occur in the proximity of freshwater springs and range in age from modern hunter-gatherer camps to early hominin sites (1.8 Ma). The goal was to determine the “sphere of influence” of the springs and estimate it's area. The study sites included spring-fed rivers and springs on lake margin flats. No archaeological sites were found at a spring, but some were as close as 100-200 m. This distance of the site from the spring is likely determined by a delicate balance between the positive factors, of the accessibility of food and dependable water, and the negative factors such as safety concerns caused by predators accessing the same resources.