The invention and proliferation of stone tool technology in the Early Stone Age (ESA) marks a watershed in human evolution. Patterns of lithic procurement, manufacture, use, and discard have much to tell us about ESA hominin cognition and land use. However, these issues cannot be fully explored outside the context of the physical attributes and spatio-temporal availability of the lithic raw materials themselves. The Olduvai Basin of northern Tanzania, which is home to both a wide variety of potential toolstones and a rich collection of ESA archaeological sites, provides an excellent opportunity to investigate the relationship between lithic technology and raw material characteristics. Here, we examine two attributes of the basin's igneous and metamorphic rocks: spatial location and fracture predictability. A total of 244 geological specimens were analyzed with non-destructive portable XRF (pXRF) to determine the geochemical distinctiveness of five primary and secondary sources, while 110 geological specimens were subjected to Schmidt rebound hardness tests to measure fracture predictability. Element concentrations derived via pXRF show significant differences between sources, and multivariate predictive models classify geological specimens with 75-80% accuracy. The predictive models identify Naibor Soit as the most likely source for a small sample of three lithic artifacts from Bed II, which supports the idea that this inselberg served as a source of toolstone during the early Pleistocene. Clear patterns in fracture predictability exist within and between both sources and rock types. Fine-grained volcanics show high rebound values (associated with high fracture predictability), while finer-grained metamorphics and coarse-grained gneisses show intermediate and low rebound values, respectively. Artifact data from Bed I and II suggest that fracture predictability played a role in raw material selection at some sites, but other attributes like durability, expediency, and nodule size and shape were more significant.
The Marmes Rockshelter archaeological site in southeastern Washington state contains a > 11 kyr stratigraphic record that was excavated in the 1960s but only recently analyzed in detail. We present the results of physical, chemical, and isotopic analyses of archived Marmes sediments from rockshelter, hillslope, and floodplain locations. Multiple lines of evidence including éboulis production, soil chemistry, and δ13C and δ18O signatures in soil organic matter and calcium carbonate suggest that relatively cool, moist conditions 10,600 to 9700 14C yr BP were followed by relatively warm and dry conditions as early as 9000 14C yr BP. Warm and dry conditions extended to the late Holocene, followed by a return to cooler and moister climate. The limited range of δ13C and δ18O values in Marmes paleosols suggests that the magnitude of moisture and temperature shifts was locally buffered in the lower Snake River Canyon but adequate to generate significant changes in sedimentation and soil formation, possibly due to nonlinear geological and pedological processes. These buffered canyon environments were well suited for establishing residential bases associated with foraging and logistical collecting strategies and may have minimized the influence of climate changes in food resource abundance.
The southern Caucasus is home to a particularly rich record of Middle Paleolithic (MP) occupation. However, the potential contribution of the southern Caucasus to broader discussions of MP behavior and adaptations has remained largely unfulfilled because many key archaeological assemblages, deriving as they do from either surface scatters or sites that were excavated without the benefit of modern archaeological techniques, lack critical contextual information. What is more, the relatively small sample of sites where such data are available has been heavily biased towards caves and rockshelters. Here, we present a preliminary report on Bagratashen 1, an open-air MP site stratified within an ancient terrace of the Debed River in northeastern Armenia. While no faunal material has yet been recovered, site formation analysis suggests that the lithic assemblage, although subjected to subaerial exposure and some degree of post-depositional alteration, is neither severely biased nor substantially reworked. The presence of numerous cores and primary flaking debris indicate that at least some reduction occurred onsite. It appears that a majority of the raw material was probably procured locally from the nearby river channel, although a handful of obsidian pieces reveal raw material movements on the order of 80 km. The Bagratashen 1 lithic assemblage also includes several elongated points that recall early MP artifacts from the Levant and other sites in the southern Caucasus that date to between 250 and 90ka BP. Optically Stimulated Luminescence samples from within the find horizon, however, returned dates of ~34ka BP. While a terminal MP date requires confirmation, Bagratashen 1 provides an interesting case with which to test the utility of formal lithic artifacts as chrono-cultural markers.
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