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Stepped-terraces systems of several tributaries of the Loire River basin were during the two last decades particular objects of multidisciplinary study, involving Quaternary geology, prehistory and geochronology. The Loire River itself, the longest stream of France, and its fossil stepped terraces system have remained little studied until now from the geochronological point of view, particularly in its middle section, near Orléans. This section is however considered for some fifty years as a key area evidencing the existence in the past of the connection of two older rivers leading to the formation of the current Loire valley. Several researchers have hence proposed the hypothesis of the existence of a Plio-Pleistocene Loire paleo-river flowing northward from the Massif Central to the Seine valley and the English Channel. This Loire River was then disconnected from this one and its flowing was orientated to the west from the Blois area until the Atlantic Ocean. The lack of alluvial deposits in the area between the present-day Loire valley and the Seine one, in relation to significant erosion, means that it is not possible to work directly on ancient evidence of the south-north paleo-river. According to the hypothesis that the alluvial terraces preserved in the intermediate sector were put in place after the connection of the two former rivers (capture), the dating of these sedimentary formations would make it possible to determine when this capture took place. Thus, a series of ESR quartz dates have made it possible to establish a chronological model for this Middle Loire. Five different phases in the evolution of the Middle Loire system can now be described, between 800ka and the present day. These phases seem to indicate a gradual capture, beginning between 900 and 800 ka, with changes in fluvial dynamics, leading to the current course of the river around 250 ka ago. [ABSTRACT FROM AUTHOR]

This study aims to provide a full synthesis of recent work on the fluvial terraces of the middle section of the Loire River, between its exit from the "Massif Central" montane area and its entry into the Touraine region, with the aim of better understanding of the evolution of the river during the Pleistocene period. New fieldwork and topographic analyses (including a predictive geomorphology approach) permit updating the spatial extent and geometry of the different Quaternary alluvial sedimentary formations in this area. In addition, new analytical data were acquired both by X-ray diffraction (XRD) on heavy minerals and by gamma spectrometry measurements on alluvial sandy sediments. These analyses allow us to characterize and distinguish the alluvial formations. This work has identified three distinct periods in the history of the Loire: the oldest, corresponding to the deposition of sediments characterised by an abundance of metamorphic minerals, originating from the Massif Central; an intermediate period, corresponding to the deposition of the high terraces of the Loire system, not characterised by mineralogical analyses but by the approach of the predicted geomorphology showing different terrace geometries; lastly, a recent period comprising the low and medium altitude terraces, characterised by an abundance of volcanic minerals also originating from the Massif Central. • A predictive geomorphology approach was used for a new mapping of the Loire terraces. • XRD and gamma-ray analyses were performed for the fluvial sediment characterisation. • Three depositional episodes were discriminated between recent and ancient formations. [ABSTRACT FROM AUTHOR]

The middle Rhône valley, located at the southeastern margins of the Massif Central in France, produced a large number of Middle Palaeolithic sites, most of which dated to the Middle and Late Pleistocene. Due to its position, connecting northern Europe and the Mediterranean basin, this corridor and the surrounding plateaus are of particular interest in the study of human cultural evolution, including the emergence of Middle Palaeolithic technology around 300,000 years ago and its variability over time, as well as the subsistence and mobility strategies of Neanderthals. In the last 20 years, several research projects undertaken in this region allowed to revise key Middle Palaeolithic sequences. This work aims at synthesising previous and new chronological data obtained by using uranium-series of speleothems and bones, infrared stimulated luminescence of feldspar and electron spin resonance of tooth enamel and quartz. We review previous ages obtained in the area and present 43 new ages that are discussed together to propose a reliable spatiotemporal framework for Neanderthal occupations. We focus on major sites in the region: Payre, Ranc-Pointu 2, Baume Flandin, Abri du Maras, Grotte des Barasses II, Abri des Pêcheurs, Grotte du Figuier and Grotte de Saint-Marcel. They all provided significant information related to the biological and behavioural evolution of Neanderthal populations on the right bank of the Rhône valley. We present here the updated chronology for the Middle Palaeolithic of this area, ranging from ca. 300,000 to 40,000 years ago. • We review the Middle Palaeolithic chronology of the Middle Rhône valley in France. • We provide 43 new ages using U-series, ESR and IRSL dating methods. • The Levallois technology is documented as early as 300 ka. • We show that Neanderthals continuously occupied the area from ca. 300 ka to 40 ka. [ABSTRACT FROM AUTHOR]