SULFUR PROXIES IN TYPE III BLACK SHALES: Fe, Mn, Co, Cu, Ni, Zn, Sc
Pat WILDE Pangloss Foundation, 1735 Highland Place Berkeley, CA 94709 email@example.com Mary S. QUINBY-HUNT Lawrence Berkeley Laboratory Berkeley, CA 94720 firstname.lastname@example.org Timothy W. LYONS Department of Earth Sciences University of California-Riverside Riverside, CA 92521-0423 email@example.com
Draft for possible submission to Salt Lake City,
Geological Society of America meeting, October 2005
Sulfur proxies using Fe, Ni, Co, and Cu developed by combining data from 51 Type III black shales (Quinby-Hunt and Wilde, 1991, 1996) from the Modern Cariaco Basin (Lyons et al., 2003) and the Devonian of New York (Werne al., 2002) are given below:
Pyrite Sulfur % = 0.000105(Fe ppm) - 1.67 R square = 0.92
Pyrite Sulfur % = 0.0179(Ni ppm) + 0.339 R square = 0.88
Pyrite Sulfur % = 0.118(Co ppm) + 0.0967 R square = 0.85
Pyrite Sulfur % = 0.0172(Cu ppm) + 0.877 R square = 0.68
PROXY REGRESSION GRAPHS I
The high correlation over nearly 400 million years suggests these sulfur-metal relationships are relatively fixed during deposition and early diagenesis. Additional sulfur proxies with Mn, Sc and Zn, were found in the Cariaco Basin, but could not be reproduced for the Devonian samples. Mn did show an intriguing negative correlation with S, which was the reverse of the correlation from the Cariaco Basin.
Modern Cariaco Basin: Pyrite Sulfur % = 0.00429(Mn ppm) + 0.503 R square = 0.85
Devonian Oakta Fm NY: Pyrite Sulfur % = - 0.042(Mn ppm) + 10.3 R square = 0.71
PROXY REGRESSION GRAPHS II
Accordingly, extrapolation of sulfur proxies using Mn, Sc, and Zn over long time spans should be used with caution. However, variations among proxies with time might be used to track various sedimentary and mineralogical processes. Obviously, more data sets of varying ages, but with similar lithologies and anoxic conditions, should be compared.
Proxies developed for the ODP site (Lyons et al., 2003) were used to estimate the unreported sulfur values for Cariaco Basin USGS core PL07-39C (Piper and Dean, 2002) located about 50 kilometers to the east. Corresponding lithologic units and ages were compared. Estimated values internally agreed within a range of 0.4 % Sulfur.
CARIACO BASIN COMPARISONS
OTHER SULFUR PROXIES GRAPHS
Lyons, T. W., Werne, J. P., and Hollander, D. J. 2003, Contrasting sulfur geochemistry and Fe/Al and Mo/Al ratios across the last oxic-to-anoxic transition in the Cariaco Basin, Venezuela: Chemical Geology, v. 195, p. 131-157 special issue: Isotopic Records of Microbially Mediated processes.
Piper, D. Z. and Dean, W. E. , 2002, Trace-Element Deposition in the Cariaco Basin,Venezuela Shelf, under Sulfate-Reducing Conditions. A History of the Local Hydrography and Global Climate, 20 Ka to the Present: US Geological Survey Prof. Paper 670, 1-41.
Quinby-Hunt. M. S. and P. Wilde, 1991, The provenance of low-calcic black shales: Mineralium Deposita, v. 26, p. 113-121.
Quinby-Hunt, M. S. and Wilde, P., 1996, Depositional environments of calcic marine black shales: Economic Geology, vol. 91, p. 4-13.
Werne, J. P., Sageman, B. B., Lyons, T. W. and Hollander, D. J., 2002, An integrated assessment of a "type euxinic" deposit: Evidence for multiple controls on black shale deposition in the Middle Devonian Oatka Creek Formation: American Journal of Science, v. 302, p. 110-143.