Challenges to reconstruct chert availability in tectonically highly modified environments: Examples from the Dead Sea Transform (Gesher Benot Ya'aqov, Wadi Hammeh, Greater Petra Region)

In the Near East, more particularly in the Southern Levant, the Rift Depression, also called the Dead Sea Transform (DST), reveals unique natural phenomena that have deeply marked the landscape, notably its topographic and hydrographic features, since the Miocene, about 5 million years ago (Mya). In this paper, we present four geo-archaeological case studies associated with the Central Jordan Valley (i.e. Gesher Benot Ya'aqov, Wadi al-Hammeh and the Greater Petra Region). These examples intend to illustrate the importance of taking the context and development of the geological substratum into account for the reconstruction of prehistoric lithic procurement strategies. Chert features and availability have been profoundly impacted by these diverse and complex processes. Continental and marine erosion, associated with plate tectonics and lateral plate displacements, have altered silicifications in their primary matrix and have also resulted in the accumulation of secondary deposits rich in chert nodules. Prehistoric peoples throughout the Pleistocene have extensively exploited these various sources. At Acheulian Gesher Benot Ya'aqov the presence of a non-local chert provided the opportunity to focus on and better understand the battered chert only available south of the Sea of Galilee, in the Central Jordan Valley (Case Study #1). The Natufian inhabitants of Wadi Hammeh 27 mainly exploited a yellow chert collected in secondary outcrops of limited geographical distribution that have vanished with the Holocene erosion (Case Study #2). In the Petra Region the lithic analysis of Neolithic assemblages was challenged by the presence of cherts of supposedly non-local origin. Lithic analysts working in the Dead Sea Rift should be aware that the chert spectrum of "the other side" of the depression might be different and that knowledge on local or regional chert availability cannot simply be transferred (Case Study #3). In the Wadi Sabra lateral and vertical displacements as well as tilting processes have affected primary chert-bearing formations resulting in heavily fissured and cracked cherts badly suitable for knapping. In contrast, the tectonically unaffected outcrops in the highlands show no internal damage of the material. This difference is clearly mirrored in the procurement behaviour of the Upper Palaeolithic groups occupying the wadi (Case Study #4).