摘要

AGES, ORIGIN AND EVOLUTION OF THE LOAM COVER OF THE LOWER PLAIN OF THE GARONNE: THE EXAMPLE OF THE ARCHAEOLOGICAL SITE OF FONTREAL (CASTELNAU-D'ESTRETEFONDS, HAUTE-GARONNE)
Preventive archaeological researches on the lower plain of the Garonne river, around the confluence with the Hers and Girou valleys, allow us to do new observations about the origin of the loam cover. Its origin has been made clearer by the stratigraphic and sedimentological studies, coupled with palaeoenvironnemental and archaeological data. This loam cover, clearly polygenic, blankets the coarse-grained alluvial body of the lower plain. It begins with loams flood deposits which cover the sandy and gravely units. A rich malacofauna was discovered and supplied convergent elements to place their accumulation at the end of the Upper Pleniglacial. In the low-lying areas of the topography, this cover was then covered by clayey silt which corresponds to the filling of paludal depressions. Their accumulation is partially synchronous with the Neolithic occupation of the Fontreal site and includes, at its base, in situ archaeological remains. The distribution of Neolithic remains shows that the topography of this area was still clearly differentiated 4000 - 5000 years ago and that the highest places were preferentially occupied. The rest of the filling, which can be more than two meters thick, is more recent and yielded abundant fragments of bricks and rolled mortar. Their presence allows us to link this important sedimentary phase with the modern period. This should be the consequence of massive deforestations on the sandy-clay hillside that dominates the site. Agricultural activities finished the complete levelling of the lower plain and gave it the uniformly flat aspect that one can see today.

  • 出版日期2010-12