TY  - JOUR
A1  - Bougeois, Laurie
A1  - de Rafelis, Marc
A1  - Reichart, Gert-Jan
A1  - de Nooijer, Lennart J.
A1  - Dupont-Nivet, Guillaume
T1  - Mg/Ca in fossil oyster shells as palaeotemperature proxy, an example from the Palaeogene of Central Asia
JF  - Palaeogeography, palaeoclimatology, palaeoecology : an international journal for the geo-sciences
N2  - Fossil oyster shells are well-suited to provide palaeotemperature proxies from geologic to seasonal timescales due to their ubiquitous occurrence from Triassic to Quaternary sediments, the seasonal nature of their shell growth and their relative strong resistance to post-mortem alteration. However, the common use to translate calcitic oxygen isotopes into palaeotemperatures is challenged by uncertainties in accounting for past seawater delta O-18, especially in shallow coastal environment where oysters calcify. In principle, the Mg/Ca ratio in oyster shells can provide an alternative palaeothermometer. Several studies provided temperature calibrations for this potential proxy based on modem species, nevertheless their application to palaeo-studies remains hitherto unexplored. Here, we show that past temperature variability in seawater can be obtained from Mg/Ca analyses from selected fossil oyster species and specimens. High-resolution Mg/Ca profiles, combined with delta O-18, were obtained along 41 fossil oyster shells of seven different species from the Palaeogene Proto-Paratethys sea (Central Asia) found in similar as well as different depositional age and environments providing comparison. Suitable Mg/Ca profiles, defined by continuous cyclicity and reproducibility within one shell, are found to be consistent for specimens of the same species but differ systematically between species, implying a dominant species-specific effect on the Mg/Ca signal. Two species studied here (Ostrea (Turkostrea) strictiplicata and Sokolowia buhsii) provide an excellent proxy for palaeoclimate reconstruction from China to Europe in Palaeogene marine sediments. More generally, the protocol developed here can be applied to identify other fossil oyster species suitable for palaeoclimate reconstructions. (C) 2015 Elsevier B.V. All rights reserved.
KW  - Palaeoclimate
KW  - Oyster
KW  - Mg/Ca
KW  - Sclerochronology
KW  - Palaeogene
KW  - Central Asia
Y1  - 2016
U6  - https://doi.org/10.1016/j.palaeo.2015.09.052
SN  - 0031-0182
SN  - 1872-616X
VL  - 441
SP  - 611
EP  - 626
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Bougeois, Laurie
A1  - Dupont-Nivet, Guillaume
A1  - de Rafelis, Marc
A1  - Tindall, Julia C.
A1  - Proust, Jean-Noel
A1  - Reichart, Gert-Jan
A1  - de Nooijer, Lennart J.
A1  - Guo, Zhaojie
A1  - Ormukov, Cholponbelk
T1  - Asian monsoons and aridification response to Paleogene sea retreat and Neogene westerly shielding indicated by seasonality in Paratethys oysters
JF  - Earth and planetary science letters
N2  - Asian climate patterns, characterised by highly seasonal monsoons and continentality, are thought to originate in the Eocene epoch (56 to 34 million years ago - Ma) in response to global climate, Tibetan Plateau uplift and the disappearance of the giant Proto-Paratethys sea formerly extending over Eurasia. The influence of this sea on Asian climate has hitherto not been constrained by proxy records despite being recognised as a major driver by climate models. We report here strongly seasonal records preserved in annual lamina of Eocene oysters from the Proto-Paratethys with sedimentological and numerical data showing that monsoons were not dampened by the sea and that aridification was modulated by westerly moisture sourced from the sea. Hot and arid summers despite the presence of the sea suggest a strong anticyclonic zone at Central Asian latitudes and an orographic effect from the emerging Tibetan Plateau. Westerly moisture precipitating during cold and wetter winters appear to have decreased in two steps. First in response to the late Eocene (34-37 Ma) sea retreat; second by the orogeny of the Tian Shan and Pamir ranges shielding the westerlies after 25 Ma. Paleogene sea retreat and Neogene westerly shielding thus provide two successive mechanisms forcing coeval Asian desertification and biotic crises.
KW  - Eocene monsoon
KW  - aridification
KW  - Paratethys sea
KW  - Central Asia
KW  - seasonality
KW  - bivalves
Y1  - 2018
U6  - https://doi.org/10.1016/j.epsl.2017.12.036
SN  - 0012-821X
SN  - 1385-013X
VL  - 485
SP  - 99
EP  - 110
PB  - Elsevier
CY  - Amsterdam
ER  -