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18The geochemical characterization of several lacustrine chert formations outcropping in the Central-19Eastern Pre-Pyrenean area is presented. Four geological formations were considered: one Upper 20Cretaceous (Tremp formation), two Oligocene (Castelltallat and Tartareu-Alberola formations) and one 21Miocene (Aragonian limestones formation). Furthermore, lacustrine cherts appearing in the 22Magdalenian levels of Forcas I and Cova Alonsé (Huesca, Spain) were also considered. Analyses were 23 done using energy-dispersive X-ray fluorescence (ED-XRF) and laser ablation inductively coupled 24 plasma mass spectrometry (LA-ICP-MS). Results show different geochemical features between 25 formations, in some cases also between outcrops, concerning major, minor and trace elements. 26 Archaeological samples from Cova Alonsé and Forcas I fit in some of the stablished groups, being the 27 dispersion area slightly different between sites. Consequently, results determine the presence of 28 diversified lithic procurement strategies. 29 30 Keywords 31 Magdalenian, lithic procurement, human mobility, geochemistry, chert 32 33 34

The geographical name of Monegros has traditionally been used to describe a high-quality, dark-coloured chert originating in a carbonate lacustrine environment, being one of the most important long-distance tracers in south-west Europe during prehistory. This chert type outcrops in the Monegros region, situated in the Ebro Basin (north-eastern Iberia), but not only there, as cherts with the same descriptions are found in other regions, some far from the homonymous area. Nevertheless, prehistorians working on the characterization of lithic sources have frequently used the term 'Monegros' to define this chert, basing their attributions solely on macroscopic descriptions. These are not sufficient as they do not allow cherts from the Monegros region to be distinguished from cherts from other regions. In this study, the area where Monegros cherts outcrop was delimited and fieldwork was carried out to identify the origin of the geological formations and the preserved outcrops. The classic approach has proved to be insufficient for this purpose, so geochemical fingerprinting using energydispersive X-ray fluorescence (ED-XRF) spectroscopy was performed. The results obtained after this first geochemical approach show that some differences can be found between the different formations in the Monegros region in terms of their major and minor components.

Abstract:In recent years, allusions to exploitation of a so-called "Monegros-type" chert have been a commonplace in archaeological literature, mostly in Iberia but also in southern France. It has been also a routine that these references did not include a true petrographic characterization, being mere de visu descriptions of those products.This work presents, for the first time, macro and microscopic characterizations of some of the most outstanding chert outcrops located in the Middle Ebro Basin. There, tertiary limestone sediments that form the top part of the flat plateau reliefs hold great quantities of chert nodules. The noteworthy erosive processes that have affected this area have facilitated the gathering of those cherts: they are easy to find either in their original location, still embedded in the limestone layers, or in secondary position along the enormous glacis that connect those flat reliefs to the river terraces. Two main flint varieties have been defined: Monegros and Evaporitic of Ebro. Both were originated in continental lacustrine environments. They are fine-grained and offer excellent knapping possibilities; hence its common use since prehistoric times to recent semi-industrial exploitations related to 18 th century gunflint productions. This paper offers a preliminary study that will be developed in a forthcoming PhD dissertation, but we also include examples of its prehistoric exploitation in the Ebro Basin and abroad.

The upper Arba de Biel Basin hosts an interesting archaeological ensemble composed by five sites that were repeatedly occupied by human groups from the Upper Magdalenian until the Chalcolithic (between ca. 15,000 and 4,500 years calBP).This work presents the first results of the petrographic study of the local chert (Las Lezas), as well as a dissection of the different strategies concerning its gathering, management and exploitation in every occupation period. The implications derived from the different contribution of local and exogenous raw materials are exposed in the final section of our work.