Seawater paleotemperature and paleosalinity evolution in neritic environments of the Mediterranean margin: insights from isotope analysis of bivalve shells

• Published in: Palaeogeography, Palaeoclimatology, Palaeoecology
• Main Authors: Briard, Justine, Pucéat, Emmanuelle, Vennin, Emmanuelle, Daëron, M., Chavagnac, V., Jaillet, R., Merle, Didier, de Rafélis, Marc
• Other Authors: Géosciences Environnement Toulouse (GET), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Biogéosciences UMR 6282 (BGS), Université de Bourgogne (UB)-Centre National de la Recherche Scientifique (CNRS), Laboratoire des Sciences du Climat et de l'Environnement Gif-sur-Yvette (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Paléocéanographie (PALEOCEAN), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Centre de Recherche en Paléontologie - Paris (CR2P), Muséum national d'Histoire naturelle (MNHN)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), ANR-16-CE31-0020,AMOR,Reconstruction modèle-données des climats du Cénozoique(2016)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2020
• Subjects: Hydrological cycle; Middle Miocene; Paleoclimate; Clumped isotopes; Climatic Optimum; Coastal environment; [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry; [SDU.STU.ST]Sciences of the Universe [physics]/Earth Sciences/Stratigraphy; Antarc*; Antarctica; Ice Sheet
• Online Access: https://hal.science/hal-02449079; https://hal.science/hal-02449079/document; https://hal.science/hal-02449079/file/1-s2.0-S0031018219308272-am.pdf; https://doi.org/10.1016/j.palaeo.2019.109582

19 pages International audience The first step of ice-sheet build-up on Antarctica at the Eocene-Oligocene boundary was followed by a phase of climate instability culminating during the Miocene with a warming event called the Middle Miocene Climate Optimum (MMCO), that ended with a marked cooling phase identified as the Middle Miocene Climate Transition (MMCT). While numerous benthic foraminifera δ18O and Mg/Ca data have been used to capture the global climate evolution during this interval of climate and ice-sheet instability, geochemical records from shallow-water carbonates still remain scarce. Yet such records are crucial to capture the diversity of regional environmental responses to global climate changes, and thus to better understand the behavior of our climate system during this critical interval. In this work, we test the potential of a multi-proxy approach (δ18O, clumped isotope (Δ47), strontium isotopes (87Sr/86Sr)) applied to bivalves recovered from the Liguro-Provencal Basin and Rhodano-Provencal basin (Northwestern of the Mediterranean Sea) to reconstruct the evolution of shallow seawater temperature and salinity in this region over the latest Oligocene to Middle Miocene interval (~10 Myrs). Our results highlight a local cooling in the northwestern Mediterranean Sea during the MMCO that contrasts with the warming observed in other regions, with seawater temperatures inferred from Δ47 analyses in the 13–18 °C range. These cool seawater temperatures recorded in the studied region during the MMCO are much cooler than those recorded in the open oceans, but are in agreement with the proliferation of bryozoan observed in the Castillon-Du-Gard area during this interval. Low bivalve δ18O values (−3.24‰ in average) are recorded during this episode are interpreted to reflect enhanced freshwater inputs, lowering local salinity and seawater δ18O. Such enhanced freshwater inputs point to a phase of enhanced hydrological cycle in the studied region, possibly linked to the global mid-Miocene warming event. ...