UMR 6249 Chrono Environnement

Arc-lès-Gray, France

UMR 6249 Chrono Environnement

Arc-lès-Gray, France

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Gutherz X.,Montpellier University | Diaz A.,Montpellier University | Menard C.,University of Toulouse II – Le Mirail | Bon F.,University of Toulouse II – Le Mirail | And 6 more authors.
Quaternary International | Year: 2014

This paper presents the lithic analysis from the stratified deposits of one of the Laas Geel rock shelters in Somaliland (Shelter 7). This set of sites identified in 2002 is composed of around 20 rock shelters, most featuring polychromic paintings attributed to the Holocene. Moreover, Shelter 7 yielded numerous remains that are divided into two major chono-cultural phases. Microlithic industries from the upper part of the deposit are ascribed to the Late Stone Age (LSA). In contrast, the industries from the lower part of the deposit feature an association of LSA characteristics (but quite different from the ones from the upper part of the deposit) with technical traits that belong to the MSA, and especially the presence of a Levallois technology. This association reintroduces the question of the existence of an industry (or facies) once labeled "Hargeisan" and characterized by mixed features from the MSA and the LSA in this part of Africa at the end of the Pleistocene. Our analysis of these industries culminates in a reconsideration of the definitions proposed by Clark in his seminal book, "The Prehistory of the Horn of Africa" (1954). This study provides new typo-technological data from the upper part of the Laas Geel Shelter 7 deposit that contribute to refining Clark's definition of the 'Somaliland Wilton' industry. In addition, the association of blade/bladelet production with typical Levallois production in the lower part of this site's deposits supports a comparison with the "Hargeisan Industry". The industries recovered from Laas Geel Shelter 7 reintroduce debates on the existence of the "Hargeisan industry" and provide new data on the technological transition between the MSA and the LSA in the Horn of Africa. © 2014 Elsevier Ltd and INQUA.


Freycon V.,CIRAD - Agricultural Research for Development | Wonkam C.,CIRAD - Agricultural Research for Development | Wonkam C.,University of Yaounde I | Fayolle A.,Ministere des Eaux | And 6 more authors.
Journal of Tropical Ecology | Year: 2015

Despite the important functional role of deep roots in withdrawing water during drought, direct measurements of root distribution are very rare in tropical rain forests. The aim of this study was to investigate the root distribution of Entandrophragma cylindricum, a common tree species in the Central African semi-deciduous rain forest, in Ferralsols and Arenosols. We dug two pits to a depth of 6 m in Ferralsols and two pits to a depth of 3 m in Arenosols, close to E. cylindricum trees. The vertical soil profiles were divided into 10 × 10-cm grid cells and the roots counted were distributed in three diameter classes. We fitted a root distribution model to our dataset. We found that vertical root distribution was shallower in Arenosols than in Ferralsols. Root penetration was not stopped even by a Ferralsol with high gravel content in its subsoil. Overall, our measurements showed that 95% of all roots were distributed to depths of between 258 and 564 cm from the soil surface, which is much deeper than the 95 cm depth previously reported in the literature for tropical rain forests. As sampling depth could explain this discrepancy, we recommend a sampling depth of at least 3-5 m to accurately estimate root distribution. The drier the dry season, the deeper the sampling depth should be. Our results are consistent with global models of root distribution in forest ecosystems, which are driven by climate variables. We thus suggest that deep rooting could be common in rain forests with a marked dry season. Copyright © 2014 Cambridge University Press.


Thiery V.,UMR 6249 Chrono Environnement | Rolin P.,UMR 6249 Chrono Environnement | Dubois M.,Laue Langevin Institute | Caumon M.-C.,CNRS Georesources lab
Gondwana Research | Year: 2015

The Variscan French Massif Central (FMC) is classically described as a stack of nappes with increasing metamorphism from the bottom (parautochthonous unit) to the top (lower and upper gneiss units). Ultra-high pressure (UHP) metamorphism was already recognized in the uppermost units, with notably coesite-bearing rocks. We report the first finding of metamorphic microdiamonds in the parautochthonous unit, revealing that the UHP event affected the whole stack of nappes and also that the pressures reached are above what was previously expected, since the presence of diamond, according to the peak temperature estimates for this unit, indicates pressures of ca. 3 GPa (i.e. 100 km depth). At the scale of the FMC, this finding adds complexity to the established models. On a broader scale, this adds evidence of similarity between this part of the belt and other UHP Variscan terranes such as the Erzgebirge and the Bohemian Massif. © 2015 International Association for Gondwana Research.

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