HR: 10:35h
AN: C11E-02    [PDF]
TI: ISOTOPIC VARIATIONS IN PERMAFROST ON THE NORTH SLOPE OF ALASKA
AU: * Conrad, M E
EM: MSConrad@lbl.gov
AF: Lawrence Berkeley National Laboratory, Mailstop 70A-4418, Berkeley, CA 94720 United States
AU: Douglas, T A
EM: Thomas.A.Douglas@erdc.usace.army.mil
AF: Cold Regions Research and Engineering Laboratory, P.O. Box 35170, Fairbanks, AK 99703 United States
AU: Woods, K N
EM: KNWoods@lbl.gov
AF: Lawrence Berkeley National Laboratory, Mailstop 70A-4418, Berkeley, CA 94720 United States
AB: Anadarko Petroleum Corporation, Maurer Technology, and the U.S. Department of Energy drilled the Hot Ice \#1 borehole on the North Slope of Alaska during March/April of 2003. Its purpose was to explore for the possible occurrence of methane hydrates in the base of the thick permafrost zone present on the North Slope. The borehole reached a depth of 425 m, passing through the bottom of the permafrost at about 380 m. The entire hole was cored, with core recovery exceeding 90%. The bedrock geology consists of interbedded sequences of siltstone, conglomerate, sandstone, coal and shale with some bitumens and/or ice lenses. The borehole represents an ideal opportunity to study geochemical signals present in the North Slope permafrost. Thirty samples, obtained over the entire length of the core, were collected for isotopic analyses and are currently being analyzed at the Center for Isotope Geochemistry at the Lawrence Berkeley National Laboratory. The samples were chosen to best determine whether any broad isotopic trends exist within the permafrost. Measurements are being made of the hydrogen and oxygen isotope ratios of the ice and the carbon isotope ratios of carbon dioxide trapped in the permafrost. In addition, the carbon isotope ratios of any methane contained in the samples will also be determined. Preliminary results for the oxygen isotope compositions of the permafrost yield $\delta$$^{18}$O values ranging from -18$\permil$ to -22$\permil$ with a general trend towards lower values in the deeper part of the core. The concentrations of the CO$_{2}$ in the samples (possibly representing dissolved inorganic carbon in the pore water?) range from 0.6 to 2.5 millimoles/liter with concentrations increasing with depth. The $\delta$$^{13}$C values of the CO$_{2}$ range from -7$\permil$ to -27$\permil$ with the lowest values in the higher concentration, deeper samples. This trend is consistent with increasing inputs of CO$_{2}$ derived from hydrocarbons/hydrates with depth and may yield insight into the affecting methane hydrate formation within the permafrost.
DE: 0330 Geochemical cycles
DE: 1040 Isotopic composition/chemistry
DE: 1655 Water cycles (1836)
DE: 1823 Frozen ground
DE: 1863 Snow and ice (1827)
SC: Cryosphere [C]
MN: 2003 Fall Meeting