From a coastal plain to an anthropized fluvial valley (NW Brittany, France): 7.3 kyr of paleoenvironmental evolution from sedimentological, palynological and paleogenomic perspectives
2024
David, Ophélie | Vidal, Muriel | Gorczyńska, Aneta | Penaud, Aurélie | Pailler, Yvan | Nicolas, Clement | Goubert, Evelyne | Stéphan, Pierre | Ollivier, Morgane | Barloy-Hubler, Frédérique | Geo-Ocean (GEO-OCEAN) ; Université de Bretagne Sud (UBS)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS) | Littoral, Environnement, Télédétection, Géomatique UMR 6554 (LETG) ; Université de Brest (UBO)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut de Géographie et d'Aménagement Régional de l'Université de Nantes (Nantes Univ - IGARUN) ; Nantes Université - pôle Humanités ; Nantes Université (Nantes Univ)-Nantes Université (Nantes Univ)-Nantes Université - pôle Humanités ; Nantes Université (Nantes Univ)-Nantes Université (Nantes Univ) | Littoral, Environnement, Télédétection, Géomatique (LETG - Brest) ; Université de Brest (UBO)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Littoral, Environnement, Télédétection, Géomatique UMR 6554 (LETG) ; Université de Brest (UBO)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut de Géographie et d'Aménagement Régional de l'Université de Nantes (Nantes Univ - IGARUN) ; Nantes Université - pôle Humanités ; Nantes Université (Nantes Univ)-Nantes Université (Nantes Univ)-Nantes Université - pôle Humanités ; Nantes Université (Nantes Univ)-Nantes Université (Nantes Univ)-Centre National de la Recherche Scientifique (CNRS)-Institut de Géographie et d'Aménagement Régional de l'Université de Nantes (Nantes Univ - IGARUN) ; Nantes Université - pôle Humanités ; Nantes Université (Nantes Univ)-Nantes Université (Nantes Univ)-Nantes Université - pôle Humanités ; Nantes Université (Nantes Univ)-Nantes Université (Nantes Univ) | Université de Brest (UBO) | Trajectoires - UMR 8215 ; Université Paris 1 Panthéon-Sorbonne (UP1)-Centre National de la Recherche Scientifique (CNRS) | Ecosystèmes, biodiversité, évolution [Rennes] (ECOBIO) ; Université de Rennes (UR)-Institut Ecologie et Environnement - CNRS Ecologie et Environnement (INEE-CNRS) ; Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des sciences de l'environnement de Rennes (OSERen) ; Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE) | ANR-17-EURE-0015,ISBlue,Interdisciplinary Graduate School for the Blue planet(2017)
International audience
Show more [+] Less [-]English. Over the Holocene (last 11.7 kyr), the Brittany coastal region has undergone major changes in response to risingsea level, climatic fluctuations and increasing anthropogenic influence. This study aims to i) accurately recon-struct the paleoenvironmental evolution of a site located on the north Brittany coast (NW France), a sector thathas not been previously investigated thoroughly, and ii) improve the detection of the anthropogenic signature inpaleoenvironmental records by using a multidisciplinary approach. To achieve these goals, we made the firstcross-correlated study in coastal Brittany region, integrating sedimentological (grain-size, X-ray fluorescence),palynological (pollen grains), and paleogenomic (on plant and mammal sedimentary ancient DNA or sedaDNA)data, which we based two 7.3 kyr-long sedimentary sequences recovered from the Kerall´e valley (Plouescat, NWBrittany).First, sedimentary and vegetation trajectories allowed us to reconstruct the evolution of past depositionalenvironments in the inner part of the Kerall´e valley. The data show a progressive sedimentary infilling of theformer alluvial plain, subjected to marine incursion between 7.3 and 6 cal ka BP, up to a continental area, totallydisconnected from tidal influence since 5.4 cal ka BP. Second, the analysis of plant and mammal sedaDNAprovided a complementary tool to the pollen analysis, enhancing our ability to accurately detect past land-usepractices. In the upstream part of the Kerall´e system, anthropogenic influence remained scarce until the lateNeolithic and seemed to be restricted to the coast, as also indicated by archaeological remains. The first sig-nificant human-driven changes in plant community composition likely date back to 4.5 cal ka BP (i.e., lateNeolithic), as also shown by the presence of domesticated mammal sedaDNA, both being in agreement with thedocumented settlement by the first metal-working societies (Bell Beaker culture) in the Plouescat area. From thenuntil 4 cal ka BP (i.e., early Bronze Age), human pressure became more obvious, with the steadily increase inanthropogenic pollen indicators, while sedaDNA of plants and mammals were affected by preservation biases. At2.7 cal ka BP (i.e., Iron Age), a new anthropic threshold was characterized by maximal forest clearing leading tosignificant human-induced soil erosion across the Kerall´e watershed. Since then, at the local scale of our study,both vegetation dynamics and the presence of domesticated mammals observed by sedaDNA attest to thedevelopment of pastoralism.
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