Os and Re concentrations and Os isotope ratios for DSDP and ODP metalliferous sediments from the Pacific Ocean (Table 1)

DOI

We report new 187Os/186Os data and Re and Os concentrations in metalliferous sediments from the Pacific to construct a composite Os isotope seawater evolution curve over the past 80 m.y. Analyses of four samples of upper Cretaceous age yield 187Os/186Os values of between 3 and 6.5 and 187Re/186Os values below 55. Mass balance calculations indicate that the pronounced minimum of about 2 in the Os isotope ratio of seawater at the K-T boundary probably reflects the enormous input of cosmogenic material into the oceans by the K-T impactor(s). Following a rapid recovery to 187Os/186Os of 3.5 at 63 Ma, data for the early and middle part of the Cenozoic show an increase in 187Os/186Os to about 6 at 15 Ma. Variations in the isotopic composition of leachable Os from slowly accumulating metalliferous sediments show large fluctuations over short time spans. In contrast, analyses of rapidly accumulating metalliferous carbonates do not exhibit the large oscillations observed in the pelagic clay leach data. These results together with sediment leaching experiments indicate that dissolution of non-hydrogenous Os can occur during the hydrogen peroxide leach and demonstrate that Os data from pelagic clay leachates do not always reflect the Os isotopic composition of seawater.New data for the late Cenozoic further substantiate the rapid increase in the 187Os/186Os of seawater during the past 15 Ma. We interpret the correlation between the marine Sr and Os isotope records during this time period as evidence that weathering within the drainage basin of the Ganges-Brahmaputra river system is responsible for driving seawater Sr and Os toward more radiogenic isotopic compositions. The positive correlation between 87Sr/86Sr and U concentration, the covariation of U and Re concentrations, and the high dissolved Re, U and Sr concentrations found in the Ganges-Brahmaputra river waters supports this interpretation. Accelerating uplift of many orogens worldwide over the past 15 Ma, especially during the last 5 Ma, could have contributed to the rapid increase in 187Os/186Os from 6 to 8.5 over the past 15 Ma. Prior to 15 Ma the marine Sr and Os record are not tightly coupled. The heterogeneous distribution of different lithologies within eroding terrains may play an important role in decoupling the supplies of radiogenic Os and Sr to the oceans and account for the periods of decoupling of the marine Sr and Os isotope records.

187Os/186Os and 187Os/188Os values are uncorrected for analytical blank and are not age corrected. Age corrections do not exceed 0.1 for the oldest samples analyzed. Analytical blanks are in all cases less than 5% of the measured Os concentration.

Supplement to: Peucker-Ehrenbrink, Bernhard; Ravizza, Gregory E; Hofmann, Albrecht W (1995): The marine 187Os/186Os record of the past 80 million years. Earth and Planetary Science Letters, 130(1-4), 155-167

Identifier
DOI https://doi.org/10.1594/PANGAEA.712118
Related Identifier IsSupplementTo https://doi.org/10.1016/0012-821X(95)00003-U
Metadata Access https://ws.pangaea.de/oai/provider?verb=GetRecord&metadataPrefix=datacite4&identifier=oai:pangaea.de:doi:10.1594/PANGAEA.712118
Provenance
Creator Peucker-Ehrenbrink, Bernhard (ORCID: 0000-0002-3819-992X); Ravizza, Gregory E; Hofmann, Albrecht W
Publisher PANGAEA
Publication Year 1995
Rights Creative Commons Attribution 3.0 Unported; https://creativecommons.org/licenses/by/3.0/
OpenAccess true
Representation
Resource Type Supplementary Dataset; Dataset
Format text/tab-separated-values
Size 321 data points
Discipline Earth System Research
Spatial Coverage (-97.995W, -63.681S, 148.575E, 32.805N); North Pacific/HILL; South Pacific/BASIN; North Pacific/CONT RISE; North Pacific/ABYSSAL FLOOR; Antarctic Ocean/PLAIN; South Pacific Ocean; North Pacific Ocean
Temporal Coverage Begin 1969-05-15T00:00:00Z
Temporal Coverage End 1989-12-09T17:00:00Z