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Sulfide, phosphate, and minor element enrichment in the New Albany Shale (Devonian-Mississippian) of southern Indiana

Thesis/Dissertation ·
OSTI ID:6760877

The upper part of the New Albany Shale is divided into three members, which in ascending order are: (1) the Morgan Trail Member, a laminated brownish-black shale; (2) the Camp Run Member, an interbedded brownish-black and greenish-gray shale; and (3) the Clegg Creek Member, also a laminated brownish-black shale. The Morgan Trail and Camp Run Members contain 5 to 6% total organic carbon (TOC) and 2% sulfide sulfur. Isotopic composition of sulfide in these members ranges from -5.0 to -20.0%. C/S plots indicate linear relationships between abundances of these elements characteristic of sediments deposited in a noneuxinic marine environment. The Clegg Creek Member contains 10 to 15% TOC and 2 to 6% sulfide sulfur. Isotopic composition of sulfide ranges from -5.0 to -40.0%. The most negative values are characteristic of syngenetic pyrite formed within an anoxic water column. Abundances of carbon and sulfur are higher and uncorrelated in this member, consistent with deposition in an euxinic environment. Further, DOP (degree of pyritization) values suggest that pyrite formation was generally iron limited throughout Clegg Creek deposition, but sulfur isotopes indicate that syngenetic (water column) pyrite becomes an important component in the sediment only in the upper part of the member. At the top of the Clegg Creek Member a zone of phosphate nodules and trace metal enrichment coincides with maximal TOC values. During euxinic deposition, phosphate and trace metals accumulated below the chemocline due to limited vertical circulation in the water column. Phosphate and trace metals released for organic matter during early diagenesis resulted in precipitation of metal-rich phosphate nodules.

Research Organization:
Indiana Univ., Bloomington, IN (USA)
OSTI ID:
6760877
Country of Publication:
United States
Language:
English