Quaternary compound incised valleys of the Roussillon coast (SE France): correlation of seismic data with core data

Abstract

A detailed study of a Pliocene to Quaternary incised-valley system located under the Roussillon coastal area (Gulf of Lion) is carried out by means of a high-resolution seismic data set (coastal lagoons and adjacent shelf area), drill reports and analysis of a cored drill (Leucate SC1) performed in 2007 on the barrier beach in the North of Leucate lagoon.The lowermost surface (S100/S200), correlated with a pebbles level on the Leucate core SC1 (R0), erosionnally overlies pliocene deposits. It is incised by a thalweg 15 m depth and deepens progressively from the coastal plain to the outer shelf and dips under the Quaternary forced regressive wedges.Above this basal surface, the infilling of the incised valley corresponds to the seismic unit U1. The lower part of U1 shows continuous sub-horizontal reflectors and is correlated (Leucate SC1) to marine muds with levels of mud-supported gravels (body B). The upper part of unit U1 comprises seismic erosional reflectors that are almost amalgamated under the barrier beach. It is correlated on the Leucate well to body C comprising coarse levels (gravels and pebbles) alternating with marine muds (lower part) and marine coarse sands (upper part). The upper part of the unit is dated 12900 cal yr B.P. This unit is interpreted as resulting of successive phases of incision and infilling due to base-level changes during Pleistocene glacial and interglacial periods. Coarse levels of sand and gravel corresponding to river stages and sands and muds shelly levels representing marine stages.The overlying units represent post-glacial late transgressive (S650) and highstand (U660, U661, U662) deposits. This system is a rare example of well preserved compound incised valleys correlated offshore with Quaternary lowstand wedges.By comparison, the incised valleys along the Atlantic coast of France are "simple" incised valleys where only the last episode of incision/infilling is observable. The Quaternary "compound" incised valleys cited in the literature represent examples of the fluvial part of incised systems, whereas the Languedoc-Roussillon incised valleys probably correspond to estuary or embayment, successively reoccupied during the various Quaternary eustatic cycles.Tectonics is the main factor controlling the depositional stratigraphic architecture. The studied area is located at the hinge point between continental uplift and marine subsidence and favoured the preservation of successive phases of erosion/infilling. The geometry of the Pliocene deposits has also an impact on the shape and orientation of the buried paleovalleys. Le système de vallées incisées composées de la côte du Roussillon (SE de la France) : corrélation des données sismiques et de foragesMots-clés. -Dépôts de vallées incisées, Quaternaire, Sismique haute résolution, Données de forages, Golfe du Lion.Résumé. -L'étude détaillée d'un système de vallées incisées quaternaires situé dans le secteur côtier du Roussillon (golfe du Lion), a été menée à partir d'un ensemble de données sismiques haute résolution, de rapport...

Quaternary "Compound" Incised Valley In A Microtidal Environment, Roussillon Continental Shelf, Western Gulf of Lions, France

“…The detailed analysis and interpretation of seismic data of the incisedvalley system and inner shelf were published recently (Labaune et al 2008;Labaune et al 2010;Tesson et al 2010). These results were integrated in a regional framework including the analysis and interpretation of mid-and outer-shelf areas (Posamentier et al 1992;Tesson et al 2000).…”

“…Pliocene Deposits.-These have been identified under the coastal plain and beach barrier (Duvail et al 2002;Duvail et al 2005;Duvail 2008) over numerous long drills logs (several hundred) stored by the Bureau de Recherches Géologiques et Minières (BRGM) and correlated with seismic profiles obtained in the Leucate lagoon and the tidal channel (Labaune 2005;Tesson et al 2005;Labaune et al 2009;Tesson et al 2010). Seismic facies present (Fig.…”

“…In order to corroborate this hypothesis, our studies have focused on the southern branch of the paleovalley system, by carrying out a dense grid of HR seismic lines on the inner and middle shelf and lagoons, and drilling a long core (SC1) onland. Seismic results, geometric sketches, and their interpretation have been presented previously Tesson et al 2010). The aim of this paper is to present new data obtained owing to the SC1 drill hole.…”

100,000 years climatic cycles recorded on very high-resolution seismic data from the Santos Basin’s upper slope during the last 800 ka

“…Note the position of core GL-854 with the small blue square (D) Sea level variations during the Pliocene and Quaternary (Miller et al, 2020) with the main climatic event. INHG: Initiation of Norther Hemisphere Glaciations, MPT: Mid-Pleistocene Transition; MBE : Mid Brunhes Event; MIS Marine Isotopic Stage. The relationship between Late Quaternary margins' stratigraphy and sea level changes is well-documented from high resolution seismic data over the world, especially for the last few 100 kacycles (e.g., Kolla et al, 2000;Schuur Duncan et al, 2000;Liu et al, 2004;Rabineau et al, 2005Rabineau et al, , 2006Berne et al, 2007;Ridente et al, 2008;Bassetti et al, 2008;Tesson et al, 2010;Le Roy et al, 2014;Lafosse et al, 2018). Several studies have been conducted on the continental shelf of Rio de Janeiro State (e.g., Pinheiro-Moreira et al, 2001;Artusi et al, 2007;Fleming et al, 2009;Maia et al, 2010;Reis et al, 2013) and suggested that the continental shelf of the Santos Basin also offers the opportunity to examine the relationship between the architecture of the Quaternary deposits and the 100 ka glacio-eustatic cycles.…”