TY - JOUR
T1 - Precessional variability of 87Sr/86Sr in the late Miocene Sorbas Basin
T2 - an interdisciplinary study of drivers of inter-basin exchange
AU - Modestou, Sevasti
AU - Simon, Dirk
AU - Gutjahr, Marcus
AU - Marzocchi, Alice
AU - Kouwenhoven, Tanja
AU - Ellam, Robert
AU - Flecker, Rachel
PY - 2017/6/9
Y1 - 2017/6/9
N2 - We present the first sub-precessional record of seawater 87Sr/86Sr isotope ratios for a marginal Mediterranean sub-basin. The sediments contained in this interval (3 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 inter-basin 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 must have a mainly positive hydrologic budget, in 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 sub-precessional resolution. A net positive hydrologic budget in marginal Mediterranean sub-basins may reconcile observations of freshwater inclusions in gypsum deposits.
AB - We present the first sub-precessional record of seawater 87Sr/86Sr isotope ratios for a marginal Mediterranean sub-basin. The sediments contained in this interval (3 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 inter-basin 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 must have a mainly positive hydrologic budget, in 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 sub-precessional resolution. A net positive hydrologic budget in marginal Mediterranean sub-basins may reconcile observations of freshwater inclusions in gypsum deposits.
U2 - 10.1002/2016PA003061
DO - 10.1002/2016PA003061
M3 - Article (Academic Journal)
JO - Paleoceanography
JF - Paleoceanography
SN - 0883-8305
ER -