Shoreface migrations at the shelf edge and sea-level changes around the Last Glacial Maximum (Gulf of Lions, NW Mediterranean)

Abstract

The Bourcart-Hérault canyon interfluve in the Gulf of Lions (NW Mediterranean) was the site of very high sedimentation (up to 2.5 m/kyr) around the Last Glacial Maximum, due to the vicinity of major fluvial systems that fed the shelf edge. Shoreface deposits and offshore muds deposited during each glacial/interglacial 100 kyr-cycle, created a repeated motif with highangle and low-angle clinoforms on seismic profiles. New detailed morphological, sedimentological and paleo-environmental data, constrained by 14 C dating, allow us to propose a scenario for the evolution of this critical area between 46 and 15 cal. kyr BP. The major seismic sequence (S5), formed as a forced regression during the overall sea-level fall between MIS-3 and MIS-2, can be sub-divided into several prograding units, which indicate that relative sea-level changes were punctuated by intervals of increased fall or slow-down, or even stillstand. Similarly, the onset of sea-level rise was marked by steps, during which wave-

Phase relationship between sea level and abrupt climate change

“…The progradation or retrogradation of the deltaic system is, in turn, driven by the interplay of eustatic sea level change, tectonic movement of the continental margin, and variations in sediment supply by rivers that continuously change the balance between the generation/reduction of accommodation space and the sediment filling of this space. However, extensive seismic studies have shown that eustatic changes played the dominant role in the Gulf of Lions (Tesson et al, 1990;Posamentier et al, 1992;Gensous and Tesson, 2003;Rabineau et al, 2005Rabineau et al, , 2006Jouet et al, 2006;Berne et al, 2007;Bassetti et al, 2008), because the long term subsidence typical of a passive continental margin acted in a longer time scale than the climatic cycles studied here and the Gulf of Lions is distant from the major glacial ice sheets. In addition, sediment or water loading only amplifies the effect of global eustatic changes .…”

“…Over the last decades several seismic investigations and dated sediment cores allowed to reconstruct the general architecture and stratigraphy of the Late Pleistocene deposits of the Gulf of Lions continental shelf (Tesson et al, 1990(Tesson et al, , 1993(Tesson et al, , 2000Berné et al, 1998;Rabineau et al, 1998Rabineau et al, , 2005Rabineau et al, , 2006Jouet et al, 2006;Bassetti et al, 2008). Those authors documented the superposition of various seismic sequences separated by major discontinuities formed in response to eustatic sea level changes.…”

Sedimentological imprint on subseafloor microbial communities in Western Mediterranean Sea Quaternary sediments

“…5b). In the Gulf of Lion, the LGM was characterized by the occurrence of cold and arid episodes (Heinrich events) (Jouet et al, 2006;Beaudouin et al, 2007). Between 20 ka and 17 ka, the sea level was low, and marine sediments in the core were characterized by the proximity of the shoreline and the river mouth at that time and by a significant terrestrial input ( Fig.…”

Overpressure within upper continental slope sediments from CPTU data, Gulf of Lion, NW Mediterranean Sea

“…Outer shelf Quaternary sequences are characterized on seismic reflection profiles by alternating steep and low angle clinoforms that correspond, respectively, to high energy (sand) and low energy (silt) sediments formed during glacial and interglacial cycles (Aloïsi 1986;Bassetti et al 2006;Berné et al 1999Berné et al , 2004Jouet et al 2006;Rabineau et al 2005;Tesson et al 2000). Such outer shelf clinoforms have been attributed to sandy shoreface and muddy offshore deposits, respectively (Berné and Gorini 2005), and related to 100 kyr glacio-eustatic cycles (Rabineau et al 2005).…”