Impacts and LIPs; 187Os/188Os signatures across the K-Pg boundary

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doi: 10.1180/minmag.2013.077.5.26
Author(s): Zaiss, Jessica; Ravizza, Greg; Schmitz, Biger
Author Affiliation(s): Primary:
University of Hawaii at Manoa, Geology and Geophysics, Honolulu, HI, United States
Lund University, Sweden
Volume Title: Goldschmidt abstracts 2013
Source: Mineralogical Magazine, 77(5), p.2575; Goldschmidt 2013, Florence, Italy, Aug. 25-30, 2013. Publisher: Mineralogical Society, London, United Kingdom. ISSN: 0026-461X
Note: In English. 3 refs.
Summary: Both impacts and large igneous provinces (LIPs) can introduce unradiogneic Os into the global ocean producing excursions to lower 187Os/188Os in pelagic sediments. The 187Os/188Os excursion caused by the late Eocene Popigai impact is consistent with abrupt addition of soluble meteoritic Os to the ocean. In contrast, previously reported 187Os/188Os excursions related to LIPs show greater variability and longer duration than the Popigai Os excursion. It is well established that the Chicxulub impact event is coincident with the K-Pg mass extinction and that eruption of the Deccan Traps began before, and continued after, the extinction event. Comparison of the Popigai excursion to the Cretaceous-Paleogene (K-Pg) boundary 187Os/188Os record provides a means of assessing whether or not eruption of the Deccan liberated significant amounts of mantle-derived Os to the ocean-atmosphere system coincident with the K-Pg mass extinction. In the Equatorial Pacific, South Atlantic and Atlantic-sector of the Southern Ocean the recovery of the marine 187Os/188Os record to higher pre-extinction levels closely resembles the shape and duration of the Os recovery from the Popigai impact event. This similarity does not support claims that the main phase of the Deccan volcanism is closely linked to the K-Pg mass extinction. However, an Indian Ocean site (ODP 738C) on the Keguelen Plateau displays 187Os/188Os ratios consistently below those from other ocean basins during the Paleogene. In close proximity to the K-Pg boundary in ODP 738C, the Os-Ir-187Os/188Os signature is unequivocally meteoritic. Upsection, low 187Os/188Os ratios as far as 4.5 m above the boundary (≈ 1.2 M.Y.) are unlikely to be related to the Chicxulub impact event. These low 187Os/188Os ratios in the Indian Ocean may be fingerprint of Paleogene LIP activity associated with either the Deccan or Kerguelen, but other interpretations are possible. The marine 187Os/188Os record allows large impact events to be differentiated from the emplacement of LIPs, and may preserve regional gradients in seawater 187Os/188Os controlled by the proximity to active volcanism.
Year of Publication: 2013
Research Program: ODP Ocean Drilling Project
Key Words: 02 Geochemistry; 12 Stratigraphy, Historical Geology and Paleoecology; Asia; Cenozoic; Chicxulub Crater; Commonwealth of Independent States; Cretaceous; Deccan Traps; Impacts; Isotope ratios; Isotopes; K-T boundary; Kerguelen Plateau; Large igneous provinces; Leg 119; Lower Paleocene; Mesozoic; Metals; ODP Site 738; Ocean Drilling Program; Os-188/Os-187; Osmium; Paleocene; Paleogene; Pelagic environment; Platinum group; Popigay Structure; Russian Federation; Sea water; Southern Ocean; Stable isotopes; Stratigraphic boundary; Stratigraphy; Tertiary; Upper Cretaceous; World ocean
Coordinates: S624233 S624232 E0824715 E0824714
S624233 S624232 E0824715 E0824714
Record ID: 2013100741
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Abstract, Copyright, Mineralogical Society of Great Britain and Ireland