Using a high resolution marine osmium isotopic record for the Late Cretaceous as a paleoclimate indicator

Author(s): Robinson, N.; Ravizza, G.
Author Affiliation(s): Primary:
University of Hawaii at Manoa, Department of Geology and Geophysics, Honolulu, HI, United States
Volume Title: AGU 2006 fall meeting
Source: Eos, Transactions, American Geophysical Union, 87( Fall Meeting Suppl.); American Geophysical Union 2006 fall meeting, San Francisco, CA, Dec. 11-15, 2006. Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 0096-3941 CODEN: EOSTAJ
Note: In English
Summary: Analyses of Os concentrations and 187Os/188Os ratios performed on bulk sediment samples from ODP 690C in the Weddell Sea yield the highest resolution marine Os isotope record available for the Maastrichtian. Comparison of this record to coeval data from Shatsky Rise (DSDP 577) and Walvis Ridge (DSDP 525) suggests three insights on the use of osmium isotopic ratios as a stratigraphic tool and paleoclimate indicator: 1) The signal recovered using a bulk sediment analysis is primarily global, however systematic offsets are seen between the three sites; 2) The pre-KT Boundary decline of 187Os/188Os recording the putative influence of Deccan volcanism (Ravizza and Peucker-Ehrenbrink 2003) close to the C29r/C30n magnetic reversal, the inflection in this decline at 187Os/188Os of approximately 0.4, and the subsequent rapid decline reflecting the influence of unradiogenic osmium from the KT impactor, are robust features of the record at all three sites; 3) Periods of sea-level lowstands identified by Miller et al. (2003, 2005) and rapid and large scale fluctuations in δ18O records (Barrera et al., 1999; Wilf et al. 2003) coincide with periods of variability in the otherwise coherent 187Os/188Os curve. Offsets in the record between the three different sites preclude high-resolution correlation of the Os isotope data in the older portions of the record. Consequently it is unclear how much of this variability might reflect changing seawater 187Os/188Os as opposed to local variations in detrital input. However, the data yield a qualitative association of periods of cooling/falling sea level with decreasing 187Os/188Os, and periods of warming/rising sea level with increasing 187Os/188Os. This suggests that a climate stabilizing feedback between rates of weathering of radiogenic continental materials and the expansion and contraction of ice sheets was operative during the latest Cretaceous.
Year of Publication: 2006
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
ODP Ocean Drilling Program
Key Words: 02 Geochemistry; 12 Stratigraphy, Historical Geology and Paleoecology; Antarctica; Atlantic Ocean; Correlation; Cretaceous; DSDP Site 525; DSDP Site 577; Deep Sea Drilling Project; Geochemical indicators; Geochemistry; Glacial environment; Glacial geology; High-resolution methods; IPOD; Ice sheets; Isotope ratios; Isotopes; Leg 113; Leg 74; Leg 86; Maestrichtian; Marine environment; Marine sediments; Mesozoic; Metals; North Pacific; Northwest Pacific; ODP Site 690; Ocean Drilling Program; Os-188/Os-187; Osmium; Pacific Ocean; Paleo-oceanography; Paleoclimatology; Paleomagnetism; Paleotemperature; Platinum group; Sea-level changes; Sediments; Senonian; Shatsky Rise; South Atlantic; Southern Ocean; Stable isotopes; Upper Cretaceous; Walvis Ridge; Weddell Sea; West Pacific
Coordinates: S290415 S290414 E0025908 E0025907
N322628 N322632 E1574324 E1574323
S650938 S650937 E0011218 E0011218
Record ID: 2007079946
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