scholarly journals Environmental insights from high-resolution (SIMS) sulfur isotope analyses of sulfides in Proterozoic microbialites with diverse mat textures

Geobiology ◽  
2017 ◽  
Vol 16 (1) ◽  
pp. 17-34 ◽  
Author(s):  
M. L. Gomes ◽  
D. A. Fike ◽  
K. D. Bergmann ◽  
C. Jones ◽  
A. H. Knoll
Keyword(s):  
High Resolution ◽  
Sulfur Isotope ◽  
Isotope Analyses

Reconstructing the response of C3 and C4 plants to decadal-scale climate change during the late Pleistocene in Southern Illinois using isotopic analyses of calcified rootlets

2007 ◽  
Vol 67 (1) ◽  
pp. 136-142 ◽  
Author(s):  
Hong Wang ◽  
Sallie E. Greenberg
Keyword(s):  
Climate Change ◽  
High Resolution ◽  
Stable Isotope ◽  
Growing Season ◽  
Grass Species ◽  
C3 And C4 Plants ◽  
Southern Illinois ◽  
Isotopic Analyses ◽  
Decadal Scale ◽  
Isotope Analyses

AbstractThe δ13C and δ18O values of well-preserved carbonate rhizoliths (CRs) provide detailed insights into changes in the abundance of C3 and C4 plants in response to approximately decadal-scale changes in growing-season climate. We performed stable isotope analyses on 35–40 CRs sampled at 1-cm intervals from an 18-cm-thick paleosol formed in southern Illinois during Wisconsin interstadial 2. Minimum δ13C values show little variation with depth, whereas maximum values vary dramatically, and average values show noticeable variability; maximum δ18O values vary less than the minimum δ18O values. These findings indicate that a diverse and stable C3 flora with a limited number of C4 grass species prevailed during this interval, and suggest that the maximum growing-season temperatures were relatively stable, but minimum growing-season temperatures varied considerably. Two general patterns characterize the relationships between the δ13C and δ18O values obtained from the 1-cm samples. In some cases, low δ13C values correspond to low δ18O values and high δ13C values correspond to high δ18O values, suggesting that cooler growing-season temperatures favored C3 and warmer growing-season temperatures favored C4 plants. In other cases, low δ13C values correspond to high δ18O values, likely suggesting that wetter growing-season conditions were favorable to C3 plants. The high density of well-preserved CRs in this paleosol provides a unique opportunity to study detailed ecological responses to high-resolution variability in growing-season climate.

Oxygen- and sulfur-isotope geochemistry of acidic groundwater discharge in British Columbia, Yukon, and District of Mackenzie, Canada

1985 ◽  
Vol 22 (11) ◽  
pp. 1689-1695 ◽  
Author(s):  
Robert O. van Everdingen ◽  
M. Asif Shakur ◽  
Frederick A. Michel
Keyword(s):  
British Columbia ◽  
Sulfur Isotope ◽  
Thiobacillus Ferrooxidans ◽  
Isotope Geochemistry ◽  
Black Shales ◽  
Metal Sulfides ◽  
Sulfide Mineralization ◽  
Middle Cambrian ◽  
Acidic Groundwater ◽  
Isotope Analyses

The Paint Pots in Kootenay National Park (British Columbia) appear to derive the Fe, Zn, Pb, and [Formula: see text] contents of their water from sulfide mineralization in Lower and Middle Cambrian carbonates. The Fe, Zn, Ni, and [Formula: see text] contents of groundwater discharging into a tributary of Engineer Creek (Yukon) are likely derived from sulfide mineralization in Devonian or Ordovician black shales exposed in the area. The high Fe and [Formula: see text] contents of a natrojarosite deposit northeast of Fort Norman (Northwest Territories) are probably derived from pyritiferous Cretaceous shales in that area. Isotope analyses of water and of dissolved and precipitated sulfur species from these three sites where acidic, heavy-metal-bearing groundwater is being discharged revealed that between 38 and 74% of the oxygen used in the subsurface oxidation of metal sulfides is supplied by H2O molecules rather than by molecular (dissolved) oxygen. The available data also suggest that lower percentages of water oxygen in the secondary sulfates reflect increasing activity of Thiobacillus ferrooxidans or similar bacteria in the oxidation process.

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