Essai de paléoécologie d'un paysage : le bassin valdainais (Drôme, France) à l'Holocène

Abstract

Attempt at the palaecology of a landscape : the Valdain Basin (Drome, France) in the Holocene. The geoarcheological research conducted on the Valdain Basin, in the middle Rhone Valley, represents an attempt to systematically study a river basin. A systemic approach has enabled us to apply some ecological concepts to the different phases of the Holocene and to answer some questions about the spatio-temporal dynamics of soils, watercourses, plants and agropastoral practices. In each area of the basin, geomorphological phenomena caused by a complex combination of factors create, transform or destroy the paleoecological records representative of past bi¬ otopes. This taphonomic heterogeneity is added to the one inherent in the initial organisation of the landscape. To cope with them, cores have been set up in multiple areas of the basin. A contextual analysis is carried out on each lithostratigraphic unit which was identified in the field from the concepts of soil micromorphology. This makes it possible to hierarchise the informations which are grouped into one unit, due to the phenomena of erosion and/or accumulation. Lastly, a comparison of geomorphological, pedological, anthracological, malacological and palynological data obtained on each pedosedimentary sequence allows us to perceive the heterogeneity of landscape and its evolution over time. A few applications of this approach are presented in this article.

Characterization and quantification of Holocene colluvial and alluvial sediments in the Valdaine Region (southern France)

“…Malacological data indicate a forested landscape during the Early-Mid Bronze Age (c. 2300-1300 bc), followed by a progressive opening of the environment during the Late Bronze age (c. 1300-750 bc), while there was a general open landscape during the Iron Age and Roman Period (750 bc-ad 500) (Berger et al, 2007b). Settlement density data published in Berger (1996) and Berger et al (2007b) show an alternation of less and more dense settlement patterns during the Bronze Age and Iron Age, while a peak in settlement density occurs during the High Roman Empire (ad 1-150). This is followed by a decrease in settlement density during the Low Roman Empire (c. ad 200-500), and especially during the early and high Middle Ages (c. ad 500-1000), again followed by peaking settlement densities from ad 1000 (Berger, 1996).…”

“…Settlement density data published in Berger (1996) and Berger et al (2007b) show an alternation of less and more dense settlement patterns during the Bronze Age and Iron Age, while a peak in settlement density occurs during the High Roman Empire (ad 1-150). This is followed by a decrease in settlement density during the Low Roman Empire (c. ad 200-500), and especially during the early and high Middle Ages (c. ad 500-1000), again followed by peaking settlement densities from ad 1000 (Berger, 1996).…”

“…Settlement density was reconstructed, taking into account the erosion and reworking of archaeological deposits. Results show an intensive occupation history since the Neolithic Period (Berger, 1996(Berger, , 2011. Settlement density peaks first during the middle Neolithic Period (c. 4500-3500 bc) (Berger, 1996).…”

“…Results show an intensive occupation history since the Neolithic Period (Berger, 1996(Berger, , 2011. Settlement density peaks first during the middle Neolithic Period (c. 4500-3500 bc) (Berger, 1996). Malacological data indicate a forested landscape during the Early-Mid Bronze Age (c. 2300-1300 bc), followed by a progressive opening of the environment during the Late Bronze age (c. 1300-750 bc), while there was a general open landscape during the Iron Age and Roman Period (750 bc-ad 500) (Berger et al, 2007b).…”

“…So far, research has focused on until now site-specific reconstructions (e.g. Berger, 1996;Berger et al, 2002;Vital et al, 1999), particular cultural period synthesis (Berger and Brochier, 2006;Berger et al, 2007a), and relationships between geomorphology and archaeological site preservation (Berger, 2011;Verhagen and Berger, 2001). Quantification of sediment sinks and flows and a sediment cascade model are still missing.…”