Changements paléogéographiques dans l’archipel de Molène, du Néolithique à aujourd’hui

Abstract : In this paper, the main paleogeographic changes of the Molene archipelago were reconstruct from the Neolithic period to the present-day by numerically simulating the holocene Relative Sea-Level (RSL) rise on a high resolution topobathymetric model. A set of 21 new sea-level index points were obtained from the sedimentological analysis (grain size analysis, foraminifera, pollens) of several sediment cores collected into salt-marshes located in the bay of Brest and in the Tresseny estuary. A regional foraminifera-based transfer function was constructed and applied to the fossil foraminiferal content in order to estimate the past RSL positions. The results suggest a rate of RSL rise about 0.9 mm/yr over the last 7000 years, leading to a reduction of the terrestrial areas of the islands, from 1000 ha to 200 ha between 7000 cal. BP and the present-day. The most important terrestrial losses were on the period 7000-5000 cal. BP, from the Early Neolithic to the Recent Neolithic, with a mean rate around 2000 m²/yr. The intertidal area recorded a significant surface decrease, from 4500 ha in the Early Neolithic to 1000 ha today. Unlike the islands, the losses have been relatively regular over time, of about 5000 m²/yr, suggesting a gradual decrease in the areas available for shellfish collection and fishing. This study shows that at the time of the Early Bronze Age, the palaeogeography of the Molène Archipelago was quite different from today. The islands and the foreshore covered wider areas and some islands were linked together (Keménèz and Litiri, Trielen and Molène). The regional synthesis of pollen analyzes carried out in the western France reveals a weakness of the cereal culture and the ruderalization of the environment. The Early Bronze Age, characterized by a strong regional societal dynamism, does not seem to be associated to an increasing anthropization of the environment in Brittany. The absence of a pollen archive dated to this period in the Molène archipelago prevents to provide a more accurate picture of the vegetation landscape.
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Submitted on : Friday, August 24, 2018 - 11:45:31 AM
Last modification on : Wednesday, September 18, 2019 - 8:32:04 PM

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  • HAL Id : hal-01861285, version 1

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Pierre Stéphan, Bernard Fichaut, Serge Suanez, David Aoustin, Dominique Marguerie. Changements paléogéographiques dans l’archipel de Molène, du Néolithique à aujourd’hui. Yvan Pailler; Clément Nicolas. Une maison sous les dunes : Beg Ar Loued, île Molène, Finistère. Identité et adaptation des groupes humains en mer d’Iroise entre les IIIe et IIe millénaires avant notre ère, Sidestone Press, pp.83-121, 2019, 978-9-088-90380-9. ⟨https://www.sidestone.com/books/une-maison-sous-les-dunes⟩. ⟨hal-01861285⟩

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