A geochemical clock in earliest Paleogene pelagic carbonates based on the impact-induced Os isotope excursion at the Cretaceous-Paleogene boundary

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doi: 10.1029/2012PA002301
Author(s): Ravizza, Greg; VonderHaar, Denys
Author Affiliation(s): Primary:
University of Hawaii at Manoa, Department of Geology and Geophysics, Honolulu, HI, United States
Volume Title: Paleoceanography
Source: Paleoceanography, 27(3). Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 0883-8305 CODEN: POCGEP
Note: In English. 65 refs.; illus.
Summary: An impact-induced osmium (Os) isotope excursion provides a unique means of assessing the completeness of marine Cretaceous-Paleogene (K-Pg) boundary sections, and surmounting challenges associated with constraining the time scale of the Earth system recovery from this extreme perturbation. A model of the recovery of seawater 187Os/188Os following the impact event allows independent estimates of the time elapsed since the impact, which can be directly compared to time estimates derived from biostratigraphy, magnetostratigraphy and cyclostratigraphy. This approach is tested using data from three deep ocean sites cored by the Ocean Drilling Program (ODP). Data from ODP 1262B (South Atlantic) and ODP 690C (Southern Ocean) display the expected 187Os/188Os minimum very close to the biostratigraphically defined K-Pg boundary and yield Os-based accumulation rate estimates similar to those obtained from magnetostratigraphy and orbital tuning. In contrast, the 187Os/188Os minimum in ODP 1209C (Western Pacific) occurs ≈9 cm below the K-Pg boundary. Low Os concentrations throughout the boundary interval and an implausibly rapid recovery to higher, pre-impact 187Os/188Os ratios provide strong evidence for a previously unrecognized gap in the K-Pg interval of Site 1209. Results presented here provide strong empirical evidence that Os isotope data are uniquely valuable in assessing the completeness and accumulation rates of earliest Paleogene sediments from the deep sea. They are of broad interest because they have implications for astronomical tuning of the geologic time scale and illustrate that whole ocean geochemical perturbations can provide an alternative to biostratigraphy for correlation and timekeeping during abrupt biotic events.
Year of Publication: 2012
Research Program: ODP Ocean Drilling Program
Key Words: 02 Geochemistry; 12 Stratigraphy, Historical Geology and Paleoecology; Atlantic Ocean; Biostratigraphy; Calcium carbonate; Carbonate rocks; Cenozoic; Chicxulub Crater; Correlation; Cretaceous; Geochemistry; Hydrochemistry; Impacts; Isotope ratios; Isotopes; K-T boundary; Leg 113; Leg 198; Leg 208; Lower Paleocene; Magnetostratigraphy; Maud Rise; Mesozoic; Metals; North Pacific; Northwest Pacific; ODP Site 1209; ODP Site 1262; ODP Site 690; Ocean Drilling Program; Os-188/Os-187; Osmium; Pacific Ocean; Paleocene; Paleocene-Eocene Thermal Maximum; Paleogene; Paleomagnetism; Pelagic environment; Platinum group; Sea water; Sedimentary rocks; Sedimentation; Sedimentation rates; Shatsky Rise; South Atlantic; Southern Ocean; Stable isotopes; Stratigraphic boundary; Tertiary; Upper Cretaceous; Walvis Ridge; Weddell Sea; West Pacific
Coordinates: S271100 S271100 E0013500 E0013400
S650938 S650937 E0011218 E0011218
N323900 N324000 E1583100 E1583000
Record ID: 2014039760
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