Show simple item record

dc.contributor.authorDalai, Tarun K.  Concept link
dc.contributor.authorRavizza, Gregory E.  Concept link
dc.contributor.authorPeucker-Ehrenbrink, Bernhard  Concept link
dc.date.accessioned2006-03-10T13:58:30Z
dc.date.available2006-03-10T13:58:30Z
dc.date.issued2005-09-12
dc.identifier.urihttps://hdl.handle.net/1912/655
dc.descriptionAuthor Posting. © The Authors, 2005. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Earth and Planetary Science Letters 241 (2006): 477-492, doi:10.1016/j.epsl.2005.11.035.en
dc.description.abstractHigh resolution records (ca. 100 kyr) of Os isotope composition (187Os/188Os) in bulk sediments from two tropical Pacific sites (ODP Sites 1218 and 1219) capture the complete Late Eocene 187Os/188Os excursion and confirm that the Late Eocene 187Os/188Os minimum, earlier reported by Ravizza and Peucker-Ehrenbrink [Earth Planet. Sci. Lett. 210 (2003) 151-165], is a global feature. Using the astronomically tuned age models available for these sites, it is suggested that the Late Eocene 187Os/188Os minimum can be placed at 34.5±0.1 Ma in the marine records. In addition, two other distinct features of the 187Os/188Os excursion that are correlatable among sections are proposed as chemostratigraphic markers which can serve as age control points with a precision of ca. ±0.1 Myr. We propose a speculative hypothesis that higher cosmic dust flux in the Late Eocene may have contributed to global cooling and early Oligocene glaciation (Oi-1) by supplying bio-essential trace elements to the oceans and thereby resulting in higher ocean productivity, enhanced burial of organic carbon and draw down of atmospheric CO2. To determine if the hypothesis that enhanced cosmic dust flux in the Late Eocene was a cause for the 187Os/188Os excursion can be tested by using the paired bulk sediment and leachate Os isotope composition, 187Os/188Os were also measured in sediment leachates. Results of analyses of leachates are inconsistent between the south Atlantic and the Pacific sites, and therefore do not yield a robust test of this hypothesis. Comparison of 187Os/188Os records with high resolution benthic foraminiferal δ18O records across the Eocene-Oligocene transition suggests that 187Os flux to the oceans decreased during cooling and ice growth leading to the Oi-1 glaciation, whereas subsequent decay of ice-sheets and deglacial weathering drove seawater 187Os/188Os to higher values. Although the precise timing and magnitude of these changes in weathering fluxes and their effects on the marine 187Os/188Os records are obscured by recovery from the Late Eocene 187Os/188Os excursion, evidence of the global influence of glaciation on supply of Os to the ocean is robust as it has now been documented in both Pacific and Atlantic records.en
dc.description.sponsorshipThis study was supported by NSF awards OCE-0118380, EAR-0215297 and EAR-0215297.en
dc.format.extent30200 bytes
dc.format.extent474044 bytes
dc.format.mimetypeapplication/pdf
dc.format.mimetypeapplication/pdf
dc.language.isoen_USen
dc.relation.urihttps://doi.org/10.1016/j.epsl.2005.11.035
dc.subjectEocene-Oligocene transitionen
dc.subjectOs-isotopeen
dc.subjectChemostratigraphyen
dc.subjectOi-1 glaciationen
dc.subjectPaleoceanographyen
dc.subjectClimate-weathering feedbacken
dc.titleThe Late Eocene 187Os / 188Os excursion : chemostratigraphy, cosmic dust flux and the early Oligocene glaciationen
dc.typePreprinten


Files in this item

Thumbnail
Thumbnail

This item appears in the following Collection(s)

Show simple item record