HR: 1340h
AN: OS23C-1331    [Abstracts]
TI: Quantifying the Bioporosity of Recent Po Delta Sediments
AU: * Locat, J
EM: locat@ggl.ulaval.ca
AF: Department of Geology and Geological Engineering Laval University, De la Medecine Street, Qu‚bec, Qc G1K 7P4 Canada
AU: Levesque, M
EM: marie-claude.levesque.3@ulaval.ca
AF: Department of Geology and Geological Engineering Laval University, De la Medecine Street, Qu‚bec, Qc G1K 7P4 Canada
AU: Lee, H
EM: hjlee@usgs.gov
AF: United States Geological survey, 345 Middlefield Road, Menlo Park, CA 94025 United States
AU: Leroueil, S
EM: serge.leroueil@gci.ulaval.ca
AF: Department of Civil Engineering, Laval University, De la Medecine Street, Qu‚bec, Qc G1K7P4 Canada
AB: As part of project EuroSTRATAFORM, a series of shallow box-core samples were collected near the Po Delta in Italy. They reveal the presence of intense biogenic structures that are believed to have a strong influence on the physical properties of the sediments as they introduce another class of porosity: bioporosity (volume of biopores/total volume of the sample). Therefore, it required that they be evaluated and quantified. Two of these cores were selected for a detailed analysis. This was done primarily using 3D CATSCAN imagery (tomographic intensity) and direct physico-chemical measurements. The tomographic intensity is a complex value controlled by many factors such as the grain size, mineralogy, consolidation, water content and porosity. Two methods were used to quantify the bioporosity: an absolute and a relative bioporosity measurements both based on the use of the tomographic intensity. The relative method takes into account the variability of the sediment densities along the core, whereas the absolute method fixes the tomographic intensity based on the mean density of sediment for the whole core. Because of the evolution of the geometry of the biogenic structures, it became clear that the relative method was much better. Results have shown that the bioporosity could reach values as high a 40% and could account for more than half of the total porosity. These results suggest that significant bias on water content measurement of the matrix thus influencing estimation of physical properties like plastic and liquid limits and the liquidity index via the bias on the matrix water content measurement.
DE: 4804 Benthic processes/benthos
DE: 3022 Marine sediments--processes and transport
DE: 3094 Instruments and techniques
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting