Late Glacial to Preboreal sea-level rise recorded by the Rhône deltaic system (NW Mediterranean)

Abstract

International audienceA unique late Glacial–Preboreal record of changes in sea-level and sediment fluxes originating from the Alps is recorded in the Rhône subaqueous delta in the Western Mediterranean Sea. The compilation of detailed bathymetric charts, together with high-resolution seismic profiles and long cores, reveals the detailed architecture of several sediment lobes, related to periods of decreased sea-level rise and/or increased sediment flux. They are situated along the retreat path of the Rhône distributaries, from the shelf edge and canyon heads up to the modern coastline. They form transgressive backstepping parasequences across the shelf, the late Holocene (highstand) deltas being confined to the inner shelf. The most prominent feature is an elongated paleo-shoreface/deltaic system, with an uppermost sandy fraction remolded into subaqueous dunes. A long piston core into the bottomsets of this prograding unit allows precise dating of this ancient deltaic system. In seismic data, it displays aggradation, starting at not, vert, similar 15 cal kyr BP, followed by progradation initiated during the first phase of the Younger Dryas, a period of reduced sea-level rise or stillstand. The delta kept pace with resumed sea-level rise during the Preboreal (which is estimated at about 1 cm/yr), as a result of increased sediment supply from the Alps (melting of glaciers and more humid climate “flushing” the sediment down to the sea). Abandonment of the delta occurred around 10,500 cal yr BP, that is to say about 1000 yr after the end of the Younger Dryas, probably because of decreased sediment flux

Holocene hydrological changes in the Rhône River (NW Mediterranean) as recorded in the marine mud belt

“…The disconnection between the river and the canyon head is dated to 19 ka cal BP in response to rapid sea-level rise (Lombo Tombo et al, 2015). The landward retreat path of Gensous and Tesson, 2003;Berné et al, 2007;Jouet, 2007;Fanget et al, 2014;Lombo Tombo et al, 2015). ERDC: Early Rhône Deltaic Complex.…”

“…the estuary mouth on the shelf has been tracked through the mapping and dating of paleodelta lobes (Berné et al, 2007;Fanget et al, 2014;Gensous and Tesson, 2003;Jouet, 2007;Lombo Tombo et al, 2015) and, onshore, through the study of ancestral beach ridges (Arnaud-Fassetta, 1998;L'Homer et al, 1981;Vella and Provansal, 2000). During the Younger Dryas, an "Early Rhône Deltaic Complex" (ERDC) formed at depths between −50 and −40 m below the present sea level (Berné et al, 2007).…”

“…During the Younger Dryas, an "Early Rhône Deltaic Complex" (ERDC) formed at depths between −50 and −40 m below the present sea level (Berné et al, 2007). The estuary then shifted to the NW as the sea level rose during the early Holocene (Fanget et al, 2014).…”

A 500 kyr record of global sea-level oscillations in the Gulf of Lion, Mediterranean Sea: new insights into MIS 3 sea-level variability

“…3g and 4b), as illustrated by the modern Holocene epicontinental prism extending down to 90 m water depth over the inner shelf (Aloïsi, 1986;Berné et al, 2007Berné et al, , 2004b. Obviously, these glacial/interglacial contrasting sedimentation rates resulted in expanded glacial intervals (therefore, resulting in higher temporal resolution) and condensed interglacial intervals down the 500 kyr-long record in PRGL1-4 borehole (Fig.…”

Sedimentary archives of climate and sea-level changes during the Holocene in the Rhône prodelta (NW Mediterranean Sea)

“…BP; Mix et al, 2001), rapid sea-level rise led to the retrogradation of Rhône delta, and formation of a wedge of transgressive (backstepping) deposits thickening landward. The most prominent feature is an elongated paleo-deltaic complex, named the Early Rhône Deltaic Complex (Berné et al, 2007), which formed during the Younger Dryas and the Preboreal (Fig. 1).…”