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

Modestou, Sevasti, Simon, Dirk, Gutjahr, Marcus, Marzocchi, Alice, Kouwenhoven, Tanja J., Ellam, Rob M. and Flecker, Rachel (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.

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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.

Document Type: Article
Keywords: strontium; late Miocene; Sorbas Basin; box model; hydrologic budget; Mediterranean
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-MG Marine Geosystems
Refereed: Yes
DOI etc.: 10.1002/2016PA003061
ISSN: 0883-8305
Related URLs:
Projects: MEDGATE
Date Deposited: 26 Jun 2017 08:34
Last Modified: 10 Dec 2017 00:38

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