FLUCTUATIONS IN GROUNDWATER DISCHARGE IN THE EGYPTIAN WESTERN DESERT: IMPLICATIONS FOR ARCHAEOLOGICAL SITE FORMATION, SITE PRESERVATION, AND PALEOCLIMATE

Periodic groundwater discharge along the Libyan Escarpment and on the floors of the oasis depressions throughout Quaternary time provided the water resources necessary for human occupation of the region. The spring carbonates, or tufas, precipitated from this groundwater discharge, as well as the spring mounds on the depression floors, represent the best deposits in the Western Desert to find stratified artifacts in directly datable contexts. Groundwater sapping of the escarpment’s limestone cap, however, resulted in significant slumping of both the Eocene cap limestone and the overlying spring carbonates at certain localities. Repeated episodes of slumping and groundwater discharge from the slump scarps produced a complex stratigraphy containing artifacts which are often reworked. The chemical and isotopic composition of the spring carbonates can be used to infer groundwater chemistry during pluvial phases. As rainfall and thus groundwater discharge decreased throughout late Holocene time, inhabitants of Egypt’s Western Desert developed increasingly complex technology to gather groundwater. The qanat system at Umm el Dabadib, constructed by the Romans, or perhaps inherited from the Persians, is one of the more complex pieces of water management infrastructure in the Western Desert. A series of tunnels brings water from the escarpment foothills to the fort and settlement at Umm el Dabadib. The largest living acacia trees (Acacia niloticus ) to be found in the desert oases of western Egypt are growing along the line of the water collection tunnels. There are no young acacias associated with the older trees, suggesting that the older trees were established when groundwater levels were higher. These acacias may preserve in their rings a record of groundwater fluctuations which can be used to evaluate the pace of climate change in the Western Desert on the scale of centuries.