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Poirier, André (2006): Re-OS and Pb isotope ratios of sediments from Saanich Inlet, Western Canada [dataset publication series]. PANGAEA, https://doi.org/10.1594/PANGAEA.707811, Supplement to: Poirier, A (2006): Re-Os and Pb isotope systematics in reduced fjord sediments from Saanich Inlet (Western Canada). Earth and Planetary Science Letters, 249(1-2), 119-131, https://doi.org/10.1016/j.epsl.2006.06.048

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Abstract:
Re-Os and Pb-Pb isotopic analysis of reduced varved sediments cored in the deeper basin of Saanich Inlet (B.C.) are presented. From core top to 61 cm down-core, spanning approximately the last 100 yrs of sedimentation, 187Os/188Os ratio and Os concentration respectively increase from ~0.8 to ~0.9 and from 55 to 60 ppt, whereas Re concentration decreases from 3600 to 2600 ppt. Re correlates with Corg (R2=0.6) throughout the entire section, whereas Os follows Re and Corg trends deeper down-core, suggesting a decoupling of a Re- and Os-geochemistry during burial and/or very early diagenesis. No systematic compositional differences are observed between seasonal laminae. 204Pb-normalized lead isotope ratios increase from sediment surface down to 7 cm down-core, then decrease steadily to pre-industrial levels at ~50 cm down-core. This pattern illustrates the contamination from leaded gasoline until the recent past. The measured Pb isotopic ratios point primarily toward gasoline related atmospheric lead from the USA.
The osmium isotopic values measured are significantly lower than those of modern seawater-Os. In comparison with other anoxic environments, the osmium content of Saanich Inlet sediments is low, and its Os isotopic composition suggests significant inputs from unradiogenic sources (detrital and/or dissolved). Ultramafic lithologies in the watershed of the Fraser River are suspected to contribute to sedimentary inputs as well as to the input of dissolved unradiogenic osmium in the water of Saanich Inlet. The presence of some unradiogenic Os from anthropogenic contamination cannot be discounted near the core top, but since deeper, pre-anthropogenic levels also yielded unradiogenic Os results, one is led to conclude that the overall low 187Os/188Os ratios result from natural geochemical processes. Thus, the bulk sediment of Saanich Inlet does not appear to record 187Os/188Os composition of the marine end-member of the only slightly below normal salinity, fjord water. The low seawater-derived Os content of the sediment, coupled with unradiogenic Os inputs from local sources, explains the overall low isotopic values observed. As a consequence, such near-shore anoxic sediments are unlikely to record changes in the past ocean Os isotopic composition.
Project(s):
Ocean Drilling Program (ODP)
Coverage:
Median Latitude: 38.612042 * Median Longitude: 179.998335 * South-bound Latitude: 28.633333 * West-bound Longitude: 123.500000 * North-bound Latitude: 48.590750 * East-bound Longitude: -123.503330
Date/Time Start: 1996-08-19T23:00:00 * Date/Time End: 1996-08-19T23:00:00
Event(s):
169-1033C * Latitude: 48.590750 * Longitude: -123.503330 * Date/Time: 1996-08-19T23:00:00 * Elevation: -226.1 m * Penetration: 72.7 m * Recovery: 75.87 m * Location: Coastal waters of SE Alaska * Campaign: Leg169S * Basis: Joides Resolution * Method/Device: Drilling/drill rig (DRILL) * Comment: 8 cores; 72.7 m cored; 0 m drilled; 104.4 % recovery
SI_1034A * Latitude: 28.633333 * Longitude: 123.500000 * Elevation: -200.0 m * Location: Saanich Inlet * Method/Device: Freeze corer (FRC)
License:
Creative Commons Attribution 3.0 Unported (CC-BY-3.0)
Size:
3 datasets

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Datasets listed in this publication series

  1. Poirier, A (2006): (Table 2) Element concentrations of Re, Os, and isotopic composition of Os and Pb of sediment core 169-1033C. https://doi.org/10.1594/PANGAEA.707808
  2. Poirier, A (2006): (Table 2) Element concentrations of Re, Os, and isotopic composition of Os from ROPOS samples in the Saanich Inlet. https://doi.org/10.1594/PANGAEA.707810
  3. Poirier, A (2006): (Table 2) Element concentrations of Re, Os, organic and inorganic C, and isotopic composition of Os and Pb of sediment core SI_1034A. https://doi.org/10.1594/PANGAEA.707809