HR: 1340h
AN: OS43A-0540    [Abstracts]
TI: Using Gamma ray and Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) to Evaluate Elemental Sequences in Cap-carbonates and Cap-like Carbonates of the Death Valley Region
AU: * Holter, S A
EM: saholter@stthomas.edu
AF: University of St. Thomas, 2115 Summit Ave., St. Paul, MN 55105 United States
AU: Theissen, K M
EM: kmtheissen@stthomas.edu
AF: University of St. Thomas, 2115 Summit Ave., St. Paul, MN 55105 United States
AU: Hickson, T A
EM: tahickson@stthomas.edu
AF: University of St. Thomas, 2115 Summit Ave., St. Paul, MN 55105 United States
AU: Bostick, B
EM: bbostick@dartmouth.edu
AF: Dartmouth College, 6105 Fairchild Hall, Hanover, NH 03755 United States
AB: The Snowball Earth theory of Hoffman et al. (1998) proposes dramatic post-glacial chemical weathering as large concentrations of carbon were removed from the atmosphere. This would result in a large input of terrigenous material into the oceans; hence, we might expect that carbonates formed under these conditions would demonstrate elevated K, U, Th levels in comparison to carbonates formed under more typical conditions. In January of 2004 we collected spectral gamma data (K, U, Th) and hand samples from cap carbonates (Noonday Dolomite) and cap-like carbonates (Beck Spring Dolomite) of the Death Valley region in order to explore elemental changes in post-snowball Earth oceans. Based on our spectral gamma results, Th/U ratio trends suggested variations in the oxidation state of the Precambrian ocean. We pursued further investigations of trace elements to ascertain the reliability of these results by using ICP-OES. A suite of 25 trace elements was measured, most notably including U and Th. The ICP-OES data not only allow us to compare elemental changes between cap-carbonates and cap-like carbonates, but they also allow for a comparison of optical emission spectrometry and hand held gamma spectrometry methods. Both methods show similar trends in U and Th values for both the cap-carbonates and cap-like carbonates.
DE: 9619 Precambrian
DE: 4200 OCEANOGRAPHY: GENERAL
DE: 4267 Paleoceanography
DE: 4800 OCEANOGRAPHY: BIOLOGICAL AND CHEMICAL
DE: 1223 Ocean/Earth/atmosphere interactions (3339)
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting