Precessional variability of 87 Sr/86 Sr in the late Miocene Sorbas Basin: An interdisciplinary study of drivers of interbasin exchange

Modestou, S. , Simon, D., Gutjahr, M., Marzocchi, A., Kouwenhoven, T. J., Ellam, R. M. and Flecker, R. (2017) Precessional variability of 87 Sr/86 Sr in the late Miocene Sorbas Basin: An interdisciplinary study of drivers of interbasin exchange. Paleoceanography, 32(6), pp. 531-552. (doi: 10.1002/2016pa003061)

Abstract

We present the first subprecessional record of seawater 87Sr/86Sr isotope ratios for a marginal Mediterranean subbasin. The sediments contained in this interval (three precessional cycles between 6.60 and 6.55 Ma) are important because they record conditions during the transition to the Messinian Salinity Crisis (MSC; 5.97 to 5.33 Ma), an event for which many details are still poorly understood. The record, derived from planktic foraminifera of the late Miocene Sorbas Basin (SE Spain), shows brief excursions with precessional cyclicity to 87Sr/86Sr ratios higher than coeval ocean 87Sr/86Sr. The hydrologic conditions required to generate the observed record are investigated using box modeling, constrained using a new paleodepth estimate (150 to 250 m) based on benthic foraminiferal assemblages. The box model results highlight the role of climate-driven interbasin density contrast as a significant driver of, or impediment to, exchange. The results are particularly significant in the context of the MSC, where 87Sr/86Sr excursions have been interpreted purely as a consequence of physical restriction. To replicate the observed temporal patterns of lithological variations and 87Sr/86Sr isotope excursions, the Sorbas Basin “box” must have a mainly positive hydrologic budget, in contrast with the Mediterranean's negative budget during the late Miocene. This result has implications for the assumption of synchronous deposition of specific sedimentary layers (sapropels) between marginal and open Mediterranean settings at subprecessional resolution. A net positive hydrologic budget in marginal Mediterranean subbasins may reconcile observations of freshwater inclusions in gypsum deposits.

• Item Type: Articles
• Additional Information: The research leading to these results has received funding from the People Programme (Marie Curie Actions) of the European Union's Seventh Framework Programme FP7/2007-2013/ under REA grant agreement 290201 MEDGATE.
• Keywords: Palaeontology, oceanography.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Ellam, Professor Rob and Modestou, Dr Sevi
• Authors: Modestou, S., Simon, D., Gutjahr, M., Marzocchi, A., Kouwenhoven, T. J., Ellam, R. M., and Flecker, R.
• College/School: College of Science and Engineering > Scottish Universities Environmental Research Centre
• Journal Name: Paleoceanography
• Publisher: Wiley
• ISSN: 0883-8305
• ISSN (Online): 1944-9186
• Published Online: 09 June 2017
• Copyright Holders: Copyright © 2017 American Geophysical Union
• First Published: First published in Paleoceanography 32(6): 531-552
• Publisher Policy: Reproduced in accordance with the copyright policy of the publisher