Les formations littorales pléistocènes du Languedoc [Pleistocene shorelines of Languedoc

Abstract

A revision of the Golfe du Lion's coastal indicators permits, nowadays, to isolate four pleistocene transgressive levels. They correspond to four marine high-stands. The Pleistocene old level of Salses of « 27 m NGF can't be dated precisely. On the contrary the syn-vulcanic shorelines of Vias-Cap d'Agde, certified by theirs phreatic surtseyen products, of 5 m NGF high, are dated by K/Ar and paleomagnetism of paleomagnetic inversion Brunhes-Matuyama. During the Upper Pleistocene, two tyrrhenian levels are represented (stade 5). The eutyrrhenian shoreline, plentiful in the Corbieres, never overpasses 7-8 m of high in the 80 listed sites. The abundance of littoral sites attributable to the Eutyrrhenian, their sub-equality (if the shoreline is preserved) of the whole of the Corbieres and the Clape's limestone hills (here and there from the neogene gap of Narbon), pleads for a lack of later differential movements in this area. On the contrary, the materialization of slightly regressive shorelines reguarding to the regressive eutyrrhenien marina is seldom expressed precisely. The off-shore bar of the station of la Franqui, at 2,5 m high is one of the most representative structure. It has been dated by 14 C ≥ to 35 000 years and by a datation 230Th/234U, which hasn't given accurate result. The Holocene transgression, which hasn't been mentionned wittingly here, recovers to its transgressive maximum the same shorelines as Eutyrrhenian and Neotyrrhenian ages. This permanence in the position of the coastal prism for 125 000 years confirms the stability of the Golfe du Lion's margin since this period.