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Refining the mediterranean "Messinian gap" with high-precision U-Pb zircon geochronology, central and northern Italy

  • Astronomically tuned cyclic sedimentary successions provide unprecedented insight into the temporal evolution of depositional systems and major geologic events. However, placing astronomically calibrated records into an absolute time frame with confidence requires independent and precise geochronologic constraints. Astronomical tuning of the precessionally modulated sedimentary cycles of the Mediterranean Basin deposited during the Messinian Salinity Crisis (5.96-5.33 Ma) has indicated an similar to 90 k.y. "Messinian gap", corresponding to the evaporative drawdown of the Mediterranean following the closure of the Mediterranean-Atlantic gateway. In the Messinian deposits, a volcanic ash dated by Ar-40/Ar-39 geochronology was used to anchor the sedimentary cycles to the insolation curve. However, the uncertainty of the Ar-40/Ar-39 date introduces a potential two-cycle (similar to 40 k.y.) uncertainty in the tuning. Using high-precision chemical abrasion-thermal ionization mass spectrometry (CA-TIMS) U-Pb geochronology on single zirconAstronomically tuned cyclic sedimentary successions provide unprecedented insight into the temporal evolution of depositional systems and major geologic events. However, placing astronomically calibrated records into an absolute time frame with confidence requires independent and precise geochronologic constraints. Astronomical tuning of the precessionally modulated sedimentary cycles of the Mediterranean Basin deposited during the Messinian Salinity Crisis (5.96-5.33 Ma) has indicated an similar to 90 k.y. "Messinian gap", corresponding to the evaporative drawdown of the Mediterranean following the closure of the Mediterranean-Atlantic gateway. In the Messinian deposits, a volcanic ash dated by Ar-40/Ar-39 geochronology was used to anchor the sedimentary cycles to the insolation curve. However, the uncertainty of the Ar-40/Ar-39 date introduces a potential two-cycle (similar to 40 k.y.) uncertainty in the tuning. Using high-precision chemical abrasion-thermal ionization mass spectrometry (CA-TIMS) U-Pb geochronology on single zircon grains from two Messinian ash layers in Italy, we obtained dates of 5.5320 +/- 0.0046 Ma and 5.5320 +/- 0.0074 Ma with sub-precessional resolution. Combined with our astronomical tuning of the Messinian Lower Evaporites, the results refine the duration of the "Messinian gap" to at most 28 or 58 +/- 9.6 k.y., which correlates with either the TG12 glacial interval alone, or both TG12 and TG14 glacial intervals, supporting the hypothesis of a glacio-eustatic contribution in fully isolating the Mediterranean from the Atlantic Ocean. Our new U-Pb dates also allow us to infer a precessionally modulated cyclicity for the post-evaporitic deposits, and hence enable us to tune those successions to the insolation curve.show moreshow less

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Author:Domenico CosentinoORCiD, Robert Buchwaldt, Gianluca Sampalmieri, Annalisa Iadanza, Paola Cipollari, Taylor F. Schildgen, Linda A. Hinnov, Jahandar Ramezani, Samuel A. Bowring
DOI:https://doi.org/10.1130/G33820.1
ISSN:0091-7613 (print)
Parent Title (English):Geology
Publisher:American Institute of Physics
Place of publication:Boulder
Document Type:Article
Language:English
Year of first Publication:2013
Year of Completion:2013
Release Date:2017/03/26
Volume:41
Issue:3
Pagenumber:4
First Page:323
Last Page:326
Funder:Italian Ministry of Education, University and Research (MiUR); U.S. National Science Foundation [EAR 0931839]
Organizational units:Mathematisch-Naturwissenschaftliche Fakultät / Institut für Erd- und Umweltwissenschaften
Peer Review:Referiert