Présentation

Abstract

Situated on the occidental slopes of the massif of the Chartreuse, along the edge of an important lane of traffic which links the Isère valley to the comb of Savoie, the deposits of Saint-Thibaud-de-Couz offer a sequence of reference which has recorded the natural and cultural evolutions from the end of the Tardiglacial to the Holocene, with a rare accuracy. Studies of sedimentology, paleobotany (palynology and anthracology), paleozoology (hunted fauna, rodents, birds, fishes, malacofauna) work towards the reconstitution of the evolution of the paleoenvironment. The chronological control is assured by a whole range of radiometrical datations in good correlation with the pollinical biozonation. Eleven levels of human occupation are gradually introduced from the upper Magdalenian (beginning of the Bölling) to the ancient Mesolithic (end of the Preboreal). Various evolutive facies of the Epipaleolithic have been identified ; they indicate influences which come from different cultural spheres of environmental regions. The detailed study of the material culture will be published in Gallia Préhistoire, 37, 1995. The morpho-geological frame of Saint-Thibaud in linkage with the chronoclimatical and regional data gives the possibility to evoke the question of the cultural hiatus which separates the Wurmian déglaciation, fixed at about 20,000 BP, and the first human implantations dated at Saint-Thibaud and on the whole north-alpine territory, of about 13,000 BP. The classed fauna which lives essentially in the mountains is dominated by the Ibex whose period of hunting was staggered from spring to autumn. The question of the hunting of some little vertebrates (varied hare, marmot, birds) whose remains are abundant, is asked. The remains of a dog dated in the end of Dryas III have been discovered in a paleolithical level. Compared to the hunting, angling is testified by numerous remains of fishes. The tests performed on the vertebras show an angling activity at various periods of the year, from the end of winter to autumn. Through studies on hunting and angling, the site appears to be like a crossing point and a place of temporary stay. This mode of use of the site is confirmed by the obvious fact of great mobility of the groups testified by the silicious raw material traffic. The whole data of the paleoecologic and paleoclimatic of Saint-Thibaud allow us to distinguish five phases : The Bölling-Dryas III is characterized by an open area and a great instability of the slopes under a particulary contrasted and humid climate. The fauna is still profoundly marked by the presence of arctic elements supplemented by steppical, humid or mountains species indicating the juxtaposition of various biotopes. The Alleröd is distinguished by a major bioclimatical change particularly well recorded in the fauna : a rapid settling of a temperate fauna, a decrease in the open forms of space, a disappearance of the nordic species. Sedimentology records a progressive stabilisation of the slopes which corresponds to the development of the plant shelter. The Dryas III, the last glaciary recurrence, is well recorded by the pollens and sedimentology ; the animal world on the contrary is only very little marked by this oscillation. The Preboreal-Boreal period acknowledges an important development of the forest shelter with an extension of the broad-leaved trees then of the thermophyle species ; first temperate and humid, the climate gets dry from the Boreal onwards. The forest and mountain species are dominant in the fauna. The period from Atlantic to Nowadays meets with a slow-down of the detretics brought by cryoclasty, replaced by calcitical and argilous sediments. The pollens indicate an important development of the forest dominated by broad-leaved trees and thermophyles which testify to a warm and extremely humid climate. The top of the filling up has recorded the first clues of anthropical deforestation in the pollinical spectre, dated from the beginning of the Subboreal.