Seawater osmium isotope evidence for a middle Miocene flood basalt event in ferromanganese crust records.

Klemm, Veronika, Frank, Martin , Levasseur, Sylvain, Halliday, Alex N. and Hein, James R. (2008) Seawater osmium isotope evidence for a middle Miocene flood basalt event in ferromanganese crust records. Earth and Planetary Science Letters, 273 . pp. 175-187. DOI 10.1016/j.epsl.2008.06.028.

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Abstract

Three ferromanganese crusts from the northeast, northwest and central Atlantic were re-dated using osmium (Os) isotope stratigraphy and yield ages from middle Miocene to the present. The three Os isotope records do not show evidence for growth hiatuses. The reconstructed Os isotope-based growth rates for the sections older than 10 Ma are higher than those determined previously by the combined beryllium isotope (10Be/9Be) and cobalt (Co) constant-flux methods, which results in a decrease in the maximum age of each crust. This re-dating does not lead to significant changes to the interpretation of previously determined radiogenic isotope neodymium, lead (Nd, Pb) time series because the variability of these isotopes was very small in the records of the three crusts prior to 10 Ma. The Os isotope record of the central Atlantic crust shows a pronounced minimum during the middle Miocene between 15 and 12 Ma, similar to a minimum previously observed in two ferromanganese crusts from the central Pacific. For the other two Atlantic crusts, the Os isotope records and their calibration to the global seawater curve for the middle Miocene are either more uncertain or too short and thus do not allow for a reliable identification of an isotopic minimum. Similar to pronounced minima reported previously for the Cretaceous/Tertiary and Eocene/Oligocene boundaries, possible interpretations for the newly identified middle Miocene Os isotope minimum include changes in weathering intensity and/or a meteorite impact coinciding with the formation of the Nördlinger Ries Crater. It is suggested that the eruption and weathering of the Columbia River flood basalts provided a significant amount of the unradiogenic Os required to produce the middle Miocene minimum.

Document Type: Article
Keywords: large igneous provinces, osmium isotope stratigraphy, Columbia river flood basalts, Miocene minimum
Research affiliation: OceanRep > The Future Ocean - Cluster of Excellence
OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-P-OZ Paleo-Oceanography
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1016/j.epsl.2008.06.028
ISSN: 0012-821X
Projects: Future Ocean
Date Deposited: 03 Dec 2008 16:52
Last Modified: 09 Feb 2017 08:57
URI: http://oceanrep.geomar.de/id/eprint/3521

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