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2002 Denver Annual Meeting (October 27-30, 2002)

Paper No. 1
Presentation Time: 1:30 PM-5:30 PM

SULFUR AND OXYGEN ISOTOPIC COMPOSITION OF GYPSUM IN CAVES OF VIRGINIA AND WEST VIRGINIA


SWEZEY, Christopher S.1, PIATAK, Nadine M.2, SEAL II, Robert R.2 and WANDLESS, Gregory A.2, (1)US Geol Survey, Mailstop 956 National Center, Reston, VA 20192, (2)US Geol Survey, Mailstop 954 National Center, Reston, VA 20192, cswezey@usgs.gov

The isotopic compositions of sulfur and oxygen were determined for gypsum samples from several caves of Virginia and West Virginia in an attempt to identify the source or sources of sulfate. Gypsum samples were collected from the following six caves: Butler Cave (Bath County, VA), Cave Mountain Cave (Pendleton County, WV), Hamilton Cave (Pendleton County, WV), Haynes Cave (Monroe County, WV), New Trout Cave (Pendleton County, WV), and Sinnett Cave (Pendleton County, WV). All of these caves have developed within limestone of the upper Helderberg Group (Lower Devonian), except for Butler Cave (which has developed within Silurian-Devonian limestone of the lower Helderberg Group) and Haynes Cave (which has developed within the Upper Mississippian Greenbrier Limestone).

The sulfur and oxygen isotope values for the gypsum samples range from –18.4 to –1.0 per mil, and from 4.2 to 13.6 per mil, respectively. Gypsum samples from individual caves show a more limited range of isotopic values: Butler Cave, d34S=-5.2 to -1.0 per mil (n=5), d18O=4.2 to 7.3 per mil (n=4); Cave Mountain Cave, d34S=-13.0 to -3.1 per mil (n=6), d18O=10.9 to 13.6 per mil (n=3); Hamilton Cave: d34S=-11.8 to -10.3 per mil (n=4), d18O=11.2 to 11.8 per mil (n=2); Haynes Cave, d34S=-14.9 to -9.2 per mil (n=5), d18O=7.8 to 11.9 per mil (n=3); New Trout Cave, d34S=-18.4 to -7.6 per mil (n=2); Sinnett Cave, d34S=-10.7 to -7.5 per mil (n=4). The negative d34S values and their large range suggest that the sulfur in these gypsum samples was not derived from the simple dissolution and reprecipitation of marine evaporite sulfate within the stratigraphic section. Instead, the sulfate-sulfur was probably derived from the oxidation of diagenetic sulfide minerals and (or) from organically bound sulfur in nearby strata. The d18O values are consistent with values expected for sulfate derived from the weathering of sulfide minerals where the dominant oxidizing agent is oxygen dissolved in local meteoric water.

Session No. 101--Booth# 128

T60. Rivers in Karst: Processes and Applications (Posters)
Monday, 28 October 2002: 1:30 PM-5:30 PM
Geological Society of America Abstracts with Programs. Vol. 34, No. 6, September 2002, p.231
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