Sediment depths determined by comparison of grape and logging denisty data during Leg 138 Public Deposited

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  • Establishing true depths of recovered sediments is critical to determining sedimentation rates for high-resolution paleoclimatic studies. We have corrected the composite depth scale, which accounts for the entire continuous sedimentary sequence, so that sediment depths are consistent with logging depths, or "true" depths. We accomplished this by taking advantage of dual measurements of sediment density: in-situ wireline density logs and shipboard Gamma-Ray Attenuation Porosity Evaluator (GRAPE) density measurements. Inverse correlation techniques (Martinson et al., 1982) were used to map the composite GRAPE density record to the logging density record at five sites (Sites 846, 847, 849, 850, and 851). Using these mapping functions, depths on the meters composite depth scale (mcd) were transformed to logging depths, which were then used to calculate sedimentation rates and discrete sample depths. Tables are provided for converting mcd to logging depth (see CD-ROM, this volume). Our analysis shows that the GRAPE and density logging data are coherent at wavelengths longer than 80 cm. This analysis indicates that logging records are good references for establishing true depth scales in sedimentary sections and may be successful proxies for shipboard measurements over sections having incomplete or poor core recovery, within some limitations. To estimate density variability over such sections, we define an average gain function for the logging tool that can be used to scale logging data to account for the tool's attenuation. Using the mcd to logging depth transformations, age models developed from cores can be applied accurately to logging data
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  • Harris, S., T. Hagelberg, A. Mix, N. Pisias and N. Shackleton (1995). Sediment depths determined by comparisons of GRAPE and log density data on ODP Leg 138. In: Pisias, N.G., L. Mayer, T. Janecek, A. Palmer-Julson, T.H. van Andel (eds.), Proceedings of the Ocean Drilling Program, /Scientific Results/ 138, College Station, TX (Ocean Drilling Program), 47-58.
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  • description.provenance : Submitted by Mary Phan (mpscanner@gmail.com) on 2009-12-15T20:25:57Z No. of bitstreams: 1 Harris_etal_1995_ODP138.pdf: 2756404 bytes, checksum: 713aae7bbeab245ba0ed8cbbfdb0f501 (MD5)
  • description.provenance : Approved for entry into archive by Linda Kathman(linda.kathman@oregonstate.edu) on 2009-12-16T14:54:03Z (GMT) No. of bitstreams: 1 Harris_etal_1995_ODP138.pdf: 2756404 bytes, checksum: 713aae7bbeab245ba0ed8cbbfdb0f501 (MD5)
  • description.provenance : Made available in DSpace on 2009-12-16T14:54:03Z (GMT). No. of bitstreams: 1 Harris_etal_1995_ODP138.pdf: 2756404 bytes, checksum: 713aae7bbeab245ba0ed8cbbfdb0f501 (MD5) Previous issue date: 1995

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