FORMATION AND DEVELOPMENT OF DESERT PAVEMENT SURFACES OF THE EASTERN LIBYAN PLATEAU, EGYPT: IMPLICATIONS FOR ARCHAEOLOGICAL SURFACE SURVEY

The eastern Libyan Plateau near Abydos, Egypt is a high-desert environment consisting of desert pavement surfaces dissected by incised drainages, which contain a number of geomorphic settings including overhangs, caves, and alluvial fans at lower elevations. The Abydos Survey for Paleolithic Sites (ASPS) conducted a systematic survey for archaeological materials in this region, identifying and mapping occurrences of Paleolithic artifacts as well as evidence of more recent human activity. Paleolithic artifacts were identified almost exclusively on desert pavement surfaces; thus understanding the development and stability of these surfaces is essential to evaluating taphonomic effects upon artifact deposition, which will in turn inform models of land usage by hominids. Measurements of pavement surfaces included clast size and area, clast lithology, extent of clast burial, depth to bedrock, clast distribution in the subsurface, fracture orientation in surface materials, and surface slope. These data support the model of desert pavement formation through the trapping and burial of (presumably aeolian) smaller particles. A relatively clast-free zone of silt is found beneath a small Av horizon underlying pavement surfaces, following the work of Wells and McFadden since 1985. Pavement surfaces vary in lithology from 100% chert to 100% limestone, with varying levels of clast burial. The measurement of fracture orientation in chert clasts reveals a strong north-south orientation, suggesting that thermal cracking, and therefore physical weathering, is the primary process acting to break down surface clasts. The presence of refitting Paleolithic artifacts and knapping circles on even steep slopes indicates a very old and stable pavement surface, with limited disturbance by jackals and pedestrian travel. These high-desert surfaces are therefore likely to preserve archaeological materials in situ since the Middle Paleolithic, although many old surfaces have been lost to wadi downcutting. The time averaging of these surface pavements is at a minimum several tens of thousands of years, indicating that context of deposition alone will not allow for the recognition of changing land-use patterns over time.