Littoraux et vallées holocènes submergés en Baie de Concarneau (Bretagne méridionale)

Delanoë, Yann; Pinot, Jean Pierre

doi:10.3406/quate.1977.1309

Cited by 10 publications

(7 citation statements)

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“…Grain-size analysis, radiocarbon dating, and lithologic and fauna (foraminifera) descriptions were performed on core samples. The result led to a number of papers that highlight the new seismic data preserved in this paper (Andreieff et al, 1968a;Andreieff et al, 1968b;Bouysse et al, 1966;Bouysse and Le Calvez, 1967;Delanoë and Pinot, 1977;Lefort, 1975;Vanney, 1977;Visset et al, 1995;Visset et al, 1996).…”

Section: Core Datamentioning

confidence: 70%

Basement Control on Shaping and Infilling of Valleys Incised at the Southern Coast of Brittany, France

Menier¹,

Reynaud²,

Proust

et al. 2006

Incised Valleys in Time and Space

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The shape and infilling of the submerged parts of valleys incised along the southern coast of Brittany (France) have been investigated using very high-resolution seismics and a small number of piston cores. The valley location and morphology are found to be controlled mostly by submarine topography, which is marked by a well-developed fault zone that lies between the modern coast and a prominent basement-cored island and shoal complex located 5-15 km offshore. The faults controlled the shape of the valley networks and the amount of incision along the valley profile. They were probably active until the end of incision, because the valley thalwegs show scarps up to 10 meters high where they are crossed by these faults. The valleys were incised during the Quaternary lowstands of sea level, and most of the fill was emplaced during the last postglacial sea-level rise. The valley fills form a transgressive succession, consisting mainly of fluvial deposits at the base (possibly amalgamated from older sequences) overlain by tide-dominated estuarine deposits and capped by offshore muds. The most prominent internal surfaces are the tidal-and wave-ravinement surfaces. The valley-fill architecture is strongly dependent on the valley morphology (depth of incision, width of the valleys, and extent of estuarine intertidal areas). Estuarine deposits inside narrow and linear valleys are mostly aggrading muds, whereas those inside large and dendritic valleys dominantly comprise sandier, tidal-channel and bar deposits.

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Section: Core Datamentioning

confidence: 70%

Basement Control on Shaping and Infilling of Valleys Incised at the Southern Coast of Brittany, France

Menier¹,

Reynaud²,

Proust

et al. 2006

Incised Valleys in Time and Space

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“…This unit is of regional extent and has been interpreted previously as detrital limestone and dolomitized sands (Gros and Limasset, 1984;Borne and Chevalier, 1986). It has been initially attributed to the Upper Lutetian (Andreiff et al, 1968;Bouysse and Horn, 1968;Delanoë et al, 1975). Biostratigraphically Unit U2 would belong to the Lower to Middle Bartonian (Hardenbol et al, 1998in Guillocheau et al, 2003.…”

Section: Seismic Unitsmentioning

confidence: 96%

“…The sedimentary cover sequence is carbonated dominated with punctuated terrigenous episodes between Late Cretaceous and Late Miocene (Preux, 1978-Puit PENMA 1;Thinon et al, 2008). High amplitude oscillations of the mean-sea level during the Quaternary, associated with strong climatic variability, are usually considered as the main cause of shallow incision of river valleys at the top of these Neogene formations (Bouysse and Horn, 1968;Pinot, 1974;Delanoë et al, 1975Delanoë et al, , 1976Vanney, 1977;Menier et al, 2006). On the French Atlantic shelf, the valley network tapers below −50 m in depth (Pinot, 1974;Vanney, 1977;Lericolais et al, 2001;Proust et al, 2001;Chaumillon et al, 2008;Menier et al, 2010).…”

Section: Geological Settingmentioning

confidence: 96%

The paleo-Etel River incised valley on the Southern Brittany inner shelf (Atlantic coast, France): Preservation of Holocene transgression within the remnant of a middle Pleistocene incision?

Estournès¹,

Menier²,

Guillocheau³

et al. 2012

Marine Geology

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“…The area approximately covers 200 km 2 (5–6 km wide and ∼8.8 km long), between the Trévignon headlands and the Glénan Islands and above the 40 m isobaths below low astronomic tide (LAT). The slope is oriented south‐eastwards in the direction of the Tertiary Kerforne fault system (Delanoë & Pinot, 1977). On the eastern boundary, the coastal topography features a terrace of shoals, whose foot is bounded by the −20 m isobaths LAT (Delanoë & Pinot, 1977; Raimbault et al., 2018).…”

Section: Geological Settingmentioning

confidence: 99%

“…The slope is oriented south‐eastwards in the direction of the Tertiary Kerforne fault system (Delanoë & Pinot, 1977). On the eastern boundary, the coastal topography features a terrace of shoals, whose foot is bounded by the −20 m isobaths LAT (Delanoë & Pinot, 1977; Raimbault et al., 2018). The geophysical and geotechnical surveys were obtained for water depths ∼25–30 m LAT.…”

Section: Geological Settingmentioning

confidence: 99%

Characterization of gas‐bearing sediments in the coastal environment using geophysical and geotechnical data

Dusart

Tarits

Fabre

et al. 2022

Near Surface Geophysics

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Seismic investigation in marine gas-bearing sediments fails to get information below the acoustic mask created by free gas. To circumvent this problem, we combined collocated multichannel ultra-high resolution seismic imaging, marine electrical resistivity tomography (MERT) and core sampling to study the physical properties of gas-bearing sediments in the Bay of Concarneau (France). We obtained sections of compression (P-) wave velocitvalues where free gas was identified in seismic data. We tested a joint processing workflow combining the 1D inversion of the MERT data with the 2D P-wave velocity through a structural coupling between resistivity and velocity. We obtained a series of 2D resistivity models fitting the data whilst in agreement with. The resulting models showed the continuity of the geological units below the acoustic gas fronts which is associated with paleo-valley sediment infilling. We were able to demonstrate relationships between resistivity and velocity differing from superficial to deeper sediments. We established these relationships at the geophysical scale then compared the results to data from core sampliand porosity). We inferred the porosity distribution from the MERT data. At the core locations, we observed a good agreement between this geophysical scale porosity and the core data both within and outside the gas-bearing sediments. This agreement demonstrated that resistivity could be used as a proxy for porosity where no was available below gas caps. In these regions, the observed low resistivity showed a high porosity (60-70%) down to about 10-20 m in depth in contrast with the surrounding medium with porosity less than 55%. These results support the hypothesis that failures inside the paleo-valley sediment could control the gas migration

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Littoraux et vallées holocènes submergés en Baie de Concarneau (Bretagne méridionale)

Cited by 10 publications

References 0 publications

Basement Control on Shaping and Infilling of Valleys Incised at the Southern Coast of Brittany, France

Basement Control on Shaping and Infilling of Valleys Incised at the Southern Coast of Brittany, France

The paleo-Etel River incised valley on the Southern Brittany inner shelf (Atlantic coast, France): Preservation of Holocene transgression within the remnant of a middle Pleistocene incision?

Characterization of gas‐bearing sediments in the coastal environment using geophysical and geotechnical data

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