OSL signal saturation and dose rate variability: Investigating the behaviour of different statistical models

A refined chronology for the Middle and early Upper Paleolithic sequence of Riparo Mochi (Liguria, Italy)

The Riparo Mochi rock shelter, located on the Ligurian coast of Italy, is one of the most important early Upper Paleolithic sites on the Mediterranean rim. Its ∼10-m-deep stratigraphy comprises a Mousterian sequence, followed by various development stages of the Upper Paleolithic. A series of radiometric dates on marine shells bearing traces of human modification has provided a chronological framework for the final Mousterian and the Proto-Aurignacian of the site. Based on modeling results, the end of the Mousterian was dated between 44.0 and 41.8 ka cal BP (68% probability) and the beginning of the Proto-Aurignacian between 42.7 and 41.6 ka cal BP (68% probability). However, these estimates were based on a limited number of radiocarbon ages in the Mousterian levels. Here, we report new dating of the Mochi sequence using luminescence techniques, along with new radiocarbon measurements. The combination of these results using a Bayesian modeling approach allows for the first time the establishment of a more precise timing for the Mousterian occupation at the site. We show that Mousterian groups were already present at Riparo Mochi by at least 65 ka and continued to occupy the site for another 20 ka. The transition to the earliest Upper Paleolithic at the site is centered around 44.3-41.1 ka (95.4% probability), providing our best age estimate for the beginning of the Early Upper Paleolithic and the establishment of modern human groups in the Balzi Rossi. The sequence continues upward with a more evolved Aurignacian phase and a Gravettian phase starting at ∼26 ka or earlier.

Bayesian luminescence dating at Ghār-e Boof, Iran, provides a new chronology for Middle and Upper Paleolithic in the southern Zagros

Ghār-e Boof is a Paleolithic cave site in Iran well known for its rich early Upper Paleolithic Rostamian assemblages. The site is located on the edge of the Dasht-e Rostam plain in the southern Zagros. Recent excavations by the members of the Tübingen-Iranian Stone Age Research Project at Ghār-e Boof also recovered well-stratified Middle Paleolithic assemblages. Here, we provide the first detailed luminescence chronology for the Middle and Upper Paleolithic of the site. More generally, our work is the first luminescence chronology for a Middle and Upper Paleolithic site in the Zagros Mountains region in Iran. The luminescence ages for the Upper Paleolithic of Ghār-e Boof agree with published ¹⁴C dates. We applied Bayesian models specifically designed for luminescence dating using the R package 'BayLum' to incorporate the well-established stratigraphic constraints, as well as the published ¹⁴C ages with our optically stimulated luminescence (OSL) ages to improve the precision of the chronological framework. The Bayesian chronology shows a significantly improved precision of the OSL ages in particular for the upper part of the sequence where ¹⁴C ages were available. The Bayesian OSL ages for the Rostamian horizons, archaeologicalhorizon (AH) III (a-b-c), and AH IV, fall in the range of 37-42 ka (68% credible interval [CI]). Moreover, we determined a series of dates between 45 and 81 ka (68% CI) for the Middle Paleolithic strata from AH IVd to AH VI. Our results point to a demographic shift in the populations responsible for the Middle Paleolithic and the Rostamian within three millennia. This major technological change accompanied by the rise of symbolic artifacts such as personal ornaments, may or may not reflect a replacement of Neanderthals by modern humans. While we are confident that the Rostamian was made by modern humans, available information does not allow us to be sure who made the local Middle Paleolithic.

New data on settlement and environment at the Pleistocene/Holocene boundary in Sudano-Sahelian West Africa: Interdisciplinary investigation at Fatandi V, Eastern Senegal

The end of the Palaeolithic represents one of the least-known periods in the history of western Africa, both in terms of its chronology and the identification of cultural assemblages entities based on the typo-technical analyses of its industries. In this context, the site of Fatandi V offers new data to discuss the cultural pattern during the Late Stone Age in western Africa. Stratigraphic, taphonomical and sedimentological analyses show the succession of three sedimentary units. Several concentrations with rich lithic material were recognized. An in situ occupation, composed of bladelets, segments, and bladelet and flake cores, is confirmed while others concentrations of lithic materials have been more or less disturbed by erosion and pedogenic post-depositional processes. The sequence is well-dated from 12 convergent OSL dates. Thanks to the dating of the stratigraphic units and an OSL date from the layer (11,300-9,200 BCE [13.3-11.2 ka at 68%, 14.3-10.3 ka at 95%]), the artefacts are dated to the end of Pleistocene or Early Holocene. Palaeoenvironmental data suggest that the settlement took place within a mosaic environment and more precisely at the transition between the open landscape of savanna on the glacis and the plateau, and the increasingly densely-wooded alluvial corridor. These humid areas must have been particularly attractive during the dry season by virtue of their rich resources (raw materials, water, trees, and bushes). The Fatandi V site constitutes the first stratified site of the Pleistocene/Holocene boundary in Senegal with both precise geochronological and palaeoenvironmental data. It complements perfectly the data already obtained in Mali and in the rest of western Africa, and thus constitutes a reference point for this period. In any case, the assemblage of Fatandi V, with its bladelets and segments and in the absence of ceramics and grinding material, fits with a cultural group using exclusively geometric armatures which strongly differs from another group characterized by the production of bifacial armatures, accompanied in its initial phase by ceramics (or stoneware) and grinding material.