Late Cretaceous changes in oceanic currents and sediment sources in the eastern Tethys:insights from Nd isotopes and clay mineralogy

Autor: Elise Chenot, Nicolas Thibault, Nicolas Freslon, Emmanuelle Pucéat, Mohammad Javad Razmjooei, Jean-François Deconinck
Přispěvatelé: Biogéosciences [UMR 6282] [Dijon] (BGS), Centre National de la Recherche Scientifique (CNRS)-Université de Bourgogne (UB)-AgroSup Dijon - Institut National Supérieur des Sciences Agronomiques, de l'Alimentation et de l'Environnement, Bassins - Réservoirs - Ressources - U2R UPJV-UNIL 7511 (B2R), Université de Picardie Jules Verne (UPJV)-UniLaSalle, Department of Geology, Shahid Beheshti University, Department of Geosciences and Natural Resource Management [Copenhagen] (IGN), Faculty of Science [Copenhagen], University of Copenhagen = Københavns Universitet (KU)-University of Copenhagen = Københavns Universitet (KU), Carlsbergfondet CF16-0457, ANR-12-BS06-0011,Anox-Sea,Rôle de la configuration des continents dans le développement d'anoxies globales dans l'océan profond.(2012)
Jazyk: angličtina
Rok vydání: 2021
Předmět:
Zdroj: Chenot, E, Pucéat, E, Freslon, N, Deconinck, J F, Razmjooei, M J & Thibault, N 2021, ' Late Cretaceous changes in oceanic currents and sediment sources in the eastern Tethys : insights from Nd isotopes and clay mineralogy ', Global and Planetary Change, vol. 198, 103353 . https://doi.org/10.1016/j.gloplacha.2020.103353
Global and Planetary Change
Global and Planetary Change, Elsevier, 2021, 198, pp.103353. ⟨10.1016/j.gloplacha.2020.103353⟩
Global And Planetary Change (0921-8181) (Elsevier BV), 2021-03, Vol. 198, P. 103353 (18p.)
ISSN: 0921-8181
DOI: 10.1016/j.gloplacha.2020.103353
Popis: The Late Cretaceous is marked by geodynamical changes including Africa-Eurasia convergence that resulted in the narrowing of the Tethys Ocean and in ophiolite obduction along the southern margin of the various continental blocks in eastern Tethys. Geochemical and mineralogical analyses were performed on the Shahneshin section (Zagros Basin - eastern Tethys), to explore the consequences of this evolution on oceanic circulation, and to estimate the role of ophiolite weathering that can impact climate through atmospheric CO2 drawdown. [Ni] and [Cr] sharply increase in the uppermost Campanian – Maastrichtian interval and are not coeval with an increase in the Nd isotope composition (ɛNd) of the detrital fraction of the sediments. This is interpreted as reflecting weathering of the mantellic, ultramafic part of the ophiolite sequence at that time, implying that ophiolites were exposed on the continents as soon as the Coniacian in the vicinity of the Zagros Basin. Hence their weathering could have contributed to the Late Cretaceous climatic cooling. Clay mineralogy reveals an alternation of kaolinite-rich humid periods (Coniacian/Santonian and late early Campanian to latest Campanian) and kaolinite-depleted arid periods (early Campanian and the latest Campanian to late Maastrichtian). The ɛNd(t) of bathyal waters (carbonate leached fraction) appears quite radiogenic, in the range of -3.4 to -5.2 ɛ-units, about 2 to 4 ɛ-units higher than the detrital fraction. Changes in the ɛNd(t) of detrital material delivered to the Zagros Basin appear to control the ɛNd(t) of the local bottom waters from the Coniacian to the middle Campanian. By contrast, decoupling of detrital ɛNd(t) from that of the local bottom waters from the middle Campanian to the Maastrichtian points to increasing fluxes of westward flowing Pacific radiogenic water masses into the eastern Tethys at that time. These results support an intensification of the Tethyan Circumglobal Current, likely related to the narrowing of the Tethyan seaway.
Databáze: OpenAIRE
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