SULFUR PROXIES IN TYPE III BLACK SHALES: FE, MN, CO, CU, NI, ZN, SC

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 % = 0.0001(Fe ppm) - 1.67 R square = 0.92

Pyrite Sulfur % = 0.0179(Ni ppm) + 0.339 R square = 0.88

Pyrite Sulfur % = 0.0118(Co ppm) + 0.0967 R square = 0.85

Pyrite Sulfur % = 0.0172(Cu ppm) + 0.877 R square = 0.68

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

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.