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Abstract: Determining the Origin of Soil Magnetic Susceptibility Anomalies in Hydrocarbon Environments

COGOINI, MONIKA, University of Oklahoma, School of Geology & Geophysics, Norman, OK

Soil magnetic susceptibility anomalies caused by magnetic mineral authigenesis have been reported from hydrocarbon environments. The mechanisms that could be responsible for the formation of the new magnetic phases (e.g., magnetite) in such environments have only been described in theory. For example, several types of microorganisms, including magnetotactic, iron-reducing, and sulfate-reducing bacteria are capable of producing magnetic minerals. It has not been investigated, however, whether those bacteria could be responsible for the anomalous magnetic susceptibilities. The purpose of this study is to test for a biogenic origin of authigenic magnetic minerals above two oil fields, in the cap soil of a landfill, and in laboratory experiments. Magnetic susceptibility will be measured above and away from the oil fields. Samples will be analyzed for their magnetic mineralogy, magnetic characteristics, and for the presence of microorganisms that could cause the magnetic mineral formation. Furthermore, the soil of a capped landfill which has locally elevated magnetic susceptibilities will be microbiologically analyzed. In addition soil samples from control areas will be exposed to: hydrocarbons in the laboratory and magnetic susceptibilities and microbial content will be monitored over time Understanding the processes that cause anomalous magnetic susceptibilities as detected by a rapid, nearly noninvasive, and inexpensive method in hydrocarbon environments is important for hydrocarbon exploration and seepage detection in the environmental field.

AAPG Search and Discovery Article #90931©1998 AAPG Foundation Grants-in-Aid