Buried fluvial incisions as a record of Middle-Late Miocene eustasy fall on the Armorican Shelf (Bay of Biscay, France)

Type Article
Date 2010-01
Language English
Author(s) Paquet Fabien1, 5, Menier David1, Estournes Guilhem1, Bourillet Jean-FrancoisORCID2, Leroy Pascal3, Guillocheau Francois4
Affiliation(s) 1 : Univ Bretagne Sud, EA GeoArchitecture 2219, F-56017 Vannes, France.
2 : IFREMER, Ctr Brest, F-29280 Plouzane, France.
3 : IUEM, F-29280 Plouzane, France.
4 : Univ Rennes 1, CNRS, UMR Geosci Rennes 6118, F-35042 Rennes, France.
5 : Bur Rech Geol & Minieres, Geol Div, F-45060 Orleans 2, France.
Source Marine Geology (0025-3227) (Elsevier Science Bv), 2010-01 , Vol. 268 , N. 1-4 , P. 137-151
DOI 10.1016/j.margeo.2009.11.002
WOS© Times Cited 21
Keyword(s) Armorican Shelf, incised valleys, Miocene, eustasy, passive margin
Abstract High-resolution seismic data have been acquired in June 2008 on the Armorican Shelf (AS), in the northern Bay of Biscay, in order to reassess its stratigraphic architecture in detail and to study the impact of eustasy, tectonic and sediment delivery on the margin sedimentary record. Several profiles show fluvial-type incisions of several tens of meters (up to 54 m) associated to a widespread erosion surface. Several hypotheses are proposed for the stratigraphic position of this surface and incisions. We suggest Middle to Late Miocene age. Considering the relatively quiescent tectonic activity of the margin, we infer that the relative sea-level fall responsible of aerial incision on the Miocene shelf is eustasy-related. We propose the attested Serravallian-Tortonian eustatic lowstand (c. 11.6 Ma) as the key event responsible of such erosion and incision. This event marks the early beginning of the high-amplitude sea-level fluctuations that culminated during the Pleistocene and significantly controlled the present day AS morphology. The variability of vertical incision observed along single reaches can be explained by the confluence of several tributaries, the sinuosity of the channel and can be amplified by the unconsolidated nature of the Miocene substratum. The main pathways of the fluvial network corresponding to these buried valleys have been reconstructed and connections to other existing networks are proposed. (C) 2009 Elsevier B.V. All rights reserved.
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