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 - TY - JOUR A1 - Kaya, Mustafa Yücel A1 - Dupont-Nivet, Guillaume A1 - Proust, Jean‐Noël A1 - Roperch, Pierrick A1 - Bougeois, Laurie A1 - Meijer, Niels A1 - Frieling, Joost A1 - Fioroni, Chiara A1 - Altiner, Sevinç Özkan A1 - Vardar, Ezgi A1 - Barbolini, Natasha A1 - Stoica, Marius A1 - Aminov, Jovid A1 - Mamtimin, Mehmut A1 - Zhaojie, Guo T1 - Paleogene evolution and demise of the proto-Paratethys Sea in Central Asia (Tarim and Tajik basins) BT - Role of intensified tectonic activity at ca. 41 Ma JF - Basin research N2 - The proto-Paratethys Sea covered a vast area extending from the Mediterranean Tethys to the Tarim Basin in western China during Cretaceous and early Paleogene. Climate modelling and proxy studies suggest that Asian aridification has been governed by westerly moisture modulated by fluctuations of the proto-Paratethys Sea. Transgressive and regressive episodes of the proto-Paratethys Sea have been previously recognized but their timing, extent and depositional environments remain poorly constrained. This hampers understanding of their driving mechanisms (tectonic and/or eustatic) and their contribution to Asian aridification. Here, we present a new chronostratigraphic framework based on biostratigraphy and magnetostratigraphy as well as a detailed palaeoenvironmental analysis for the Paleogene proto-Paratethys Sea incursions in the Tajik and Tarim basins. This enables us to identify the major drivers of marine fluctuations and their potential consequences on Asian aridification. A major regional restriction event, marked by the exceptionally thick (<= 400 m) shelf evaporites is assigned a Danian-Selandian age (ca. 63-59 Ma) in the Aertashi Formation. This is followed by the largest recorded proto-Paratethys Sea incursion with a transgression estimated as early Thanetian (ca. 59-57 Ma) and a regression within the Ypresian (ca. 53-52 Ma), both within the Qimugen Formation. The transgression of the next incursion in the Kalatar and Wulagen formations is now constrained as early Lutetian (ca. 47-46 Ma), whereas its regression in the Bashibulake Formation is constrained as late Lutetian (ca. 41 Ma) and is associated with a drastic increase in both tectonic subsidence and basin infilling. The age of the final and least pronounced sea incursion restricted to the westernmost margin of the Tarim Basin is assigned as Bartonian-Priabonian (ca. 39.7-36.7 Ma). We interpret the long-term westward retreat of the proto-Paratethys Sea starting at ca. 41 Ma to be associated with far-field tectonic effects of the Indo-Asia collision and Pamir/Tibetan plateau uplift. Short-term eustatic sea level transgressions are superimposed on this long-term regression and seem coeval with the transgression events in the other northern Peri-Tethyan sedimentary provinces for the 1st and 2nd sea incursions. However, the 3rd sea incursion is interpreted as related to tectonism. The transgressive and regressive intervals of the proto-Paratethys Sea correlate well with the reported humid and arid phases, respectively in the Qaidam and Xining basins, thus demonstrating the role of the proto-Paratethys Sea as an important moisture source for the Asian interior and its regression as a contributor to Asian aridification. KW - aridification KW - Asia KW - biostratigraphy KW - climate KW - magnetostratigraphy KW - microfossil KW - Paleogene KW - Pamir KW - proto-Paratethys KW - regression KW - Tajik Basin KW - Tarim Basin KW - tectonism KW - westerlies Y1 - 2018 U6 - https://doi.org/10.1111/bre.12330 SN - 0950-091X SN - 1365-2117 VL - 31 IS - 3 SP - 461 EP - 486 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Yang, Wei A1 - Dupont-Nivet, Guillaume A1 - Jolivet, Marc A1 - Guo, Zhaojie A1 - Bougeois, Laurie A1 - Bosboom, Roderic A1 - Zhang, Ziya A1 - Zhu, Bei A1 - Heilbronn, Gloria T1 - Magnetostratigraphic record of the early evolution of the southwestern Tian Shan foreland basin (Ulugqat area), interactions with Pamir indentation and India-Asia collision JF - Tectonophysics : international journal of geotectonics and the geology and physics of the interior of the earth N2 - The Tian Shan range is an inherited intracontinental structure reactivated by the far-field effects of the India-Asia collision. A growing body of thermochronology and magnetostratigraphy datasets shows that the range grew through several tectonic pulses since similar to 25 Ma, however the early Cenozoic history remains poorly constrained. The time-lag between the Eocene India-Asia collision and the Miocene onset of Tian Shan exhumation is particularly enigmatic. This peculiar period is potentially recorded along the southwestern Tian Shan piedmont. There, late Eocene marine deposits of the proto-Paratethys epicontinental sea transition to continental foreland basin sediments of unknown age were recently dated. We provide magnetostratigraphic dating of these continental sediments from the 1700-m-thick Mine section integrated with previously published detrital apatite fission track and U/Pb zircon ages. The most likely correlation to the geomagnetic polarity time scale indicates an age span from 20.8 to 13.3 Ma with a marked increase in accumulation rates at 19-18 Ma. This implies that the entire Oligocene period is missing between the last marine and first continental sediments, as suggested by previous southwestern Tian Shan results. This differs from the southwestern Tarim basin where Eocene marine deposits are continuously overlain by late Eocene-Oligocene continental sediments. This supports a simple evolution model of the western Tarim basin with Eocene-Oligocene foreland basin activation to the south related to northward thrusting of the Kunlun Shan, followed by early Miocene activation of northern foreland basin related to overthrusting of the south Tian Shan. Our data also support southward propagation of the Tian Shan piedmont from 20 to 18 Ma that may relate to motion on the Talas Fergana Fault. The coeval activation of a major right-lateral strike-slip system allowing indentation of the Pamir Salient into the Tarim basin, suggests far-field deformation from the India-Asia collision zone affected the Tian Shan and the Talas Fergana fault by early Miocene. (C) 2015 Elsevier B.V. All rights reserved. KW - Magnetostratigraphy KW - Cenozoic KW - Tian Shan KW - Pamir KW - Tarim Basin KW - Tectonics Y1 - 2015 U6 - https://doi.org/10.1016/j.tecto.2015.01.003 SN - 0040-1951 SN - 1879-3266 VL - 644 SP - 122 EP - 137 PB - Elsevier CY - Amsterdam ER -