Reconstruction of a saline, lacustrine carbonate system (Priabonian, St-Chaptes Basin, SE France): Depositional models, paleogeographic and paleoclimatic implications

Abstract

A 220-meters thick carbonate-dominated succession has been deposited in shallow-water, saline lake environments during the Lower to Middle Priabonian (MP17A-MP18 mammal zones) in the Saint-Chaptes Basin (south-east France). The palaeoenvironmental, paleoclimatic and palaeogeographic significance of such salt lake carbonates has been deciphered on the basis of a multi-proxy analyses including 1) depositional and diagenetic features, 2) biological components (molluscs, benthic foraminifera, characean gyrogonites, spores and pollens), 3) carbon and oxygen stable isotopes, 4) trace elements and 5) clay mineralogy. Five stages of lacustrine system evolution have been identified: 1) freshwater closed lake under dry climate (unit U1); 2) fresh to brackish water lacustrine deltaic system with a mixed carbonate-siliciclastic sedimentation under relatively wet climatic conditions (unit U2); 3) saltwater lacustrine carbonate system under humid climatic setting (unit U3); 4) evaporitic lake (unit U4); and 5) closed lake with shallow-water carbonate sedimentation under subtropical to Mediterranean climate with dry seasons (unit U5). Upper Eocene aridification is evidenced to have started as early as the earliest Priabonian (unit U1: MP17A mammal zone). A change from humid to dryer climatic conditions is recorded between units U3 and U4. The Lower-Mid Priabonian saline lake is interpreted as an athalassic (inland) lake that have been transiently connected with neighboring salt lakes influenced by seawater and/or fed with sulfates deriving from recycling of evaporites. Maximum of connection with neighboring salt-lakes (Mormoiron Basin, Camargue and Central grabens, Hérault Basin) likely occurred during unit U3 and at the base of unit U5. The most likely sources of salts of these adjacent basins are: 1) Triassic evaporites derived from salt-diapirs (Rhône valley) or from paleo-outcrops located east of the Durance fault or offshore in the Gulf of Lion; or 2) marine incursions from the south, through Paleogene grabens in the Gulf of Lion.

Lacustrine stromatolites: Useful structures for environmental interpretation – an example from the Miocene Ebro Basin

“…(), Lettéron et al . () and Vennin et al . (), stromatolites in saline lacustrine environments have received little attention.…”

Carbonate facies‐specific stable isotope data record climate, hydrology, and microbial communities in Great Salt Lake, UT

“…Positive correlation between  18 O carb and  13 C carb are found in hydrologically closed basin lakes (Fig. 6a; 72 Talbot, 1990;Li & Ku, 1997;Lettéron et al, 2018;Martin-Bello et al, 2019)) such as GSL. It is 73 thought that  13 C DIC increases during intervals of lake level drop due to increased primary productivity by cyanobacteria and algae (Leng & Marshall, 2004).…”

Climatic evolution in Western Europe during the Cenozoic: insights from historical collections using leaf physiognomy

“…Laurent (1899) identified several vegetation belts from the "local" vegetation (with figs and Doliostrobus trees surrounding a lake) to the "regional" xerophilous vegetation, characterized by more coriaceous leaves and representative of a seasonal climate, with a dry season. The Célas paleoflora is included in carbonate strata located within a stratigraphic interval ranging from the top of the Lower Carbonate and Evaporite Formation (= LCEF, sensu Lettéron et al 2018) to the lower part of the Célas Sandstone Formation. Mammal (Remy 1985(Remy , 1994 and charophyte assemblages (Feist-Castel 1971) from upper LCEF and Célas Sandstone formations indicate a middle to late Priabonian age for the Célas paleoflora.…”