Comparison of multi-sensor spectral gamma ray tool (MGT) and conventional spectral gamma ray logs, ODP Site 1179

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doi: 10.2973/odp.proc.sr.191.004.2004
Author(s): Goldberg, D.; Meltser, A.; Myers, G.; Masterson, W.
Ocean Drilling Program, Leg 191, Shipboard Scientific Party, College Station, TX
Author Affiliation(s): Primary:
Lamont-Doherty Earth Observatory, Palisades, NY, United States
Other:
University of Tokyo, Japan
Japan Marine Science and Technology Center, Japan
Florida State University, United States
Dalhousie University, Canada
ODP/Naturalia et Biologia, France
University of Leicester, United Kingdom
Hiroshima University, Japan
Rice University, United States
Colorado School of Mines, United States
Brock University, Canada
University of Hawaii at Manoa, United States
Arhus Universitet, Denmark
Universität Bergakademie Freiberg, Federal Republic of Germany
Volume Title: Proceedings of the Ocean Drilling Program; scientific results; Northwest Pacific Seismic Observatory and hammer drill tests; covering Leg 191 of the cruises of the drilling vessel JOIDES Resolution; Yokohama, Japan, to Apra Harbor, Guam; Sites 1179-1182; 16 July-8 September 2000
Volume Author(s): Sager, William W.; Kanazawa, Toshihiko; Escutia, Carlota; Araki, Eiichiro; Arney, James E.; Carlson, Richard L.; Downey, Warna S.; Einaudi, Florence; Haggas, Sarah L.; Hayasaka, Yasutaka; Hirata, Kenji; Horner-Johnson, Benjamin C.; Mandernack, Kevin W.; McCarthy, Francine M. G.; Moberly, Ralph; Mochizuki, Masashi; Pedersen, Rikke Ohlenschlaeger; Salimullah, Ali R. M.; Shinohara, Masanao; Werner, Carl-Dietrich
Source: Proceedings of the Ocean Drilling Program; scientific results; Northwest Pacific Seismic Observatory and hammer drill tests; covering Leg 191 of the cruises of the drilling vessel JOIDES Resolution; Yokohama, Japan, to Apra Harbor, Guam; Sites 1179-1182; 16 July-8 September 2000, William W. Sager, Toshihiko Kanazawa, Carlota Escutia, Eiichiro Araki, James E. Arney, Richard L. Carlson, Warna S. Downey, Florence Einaudi, Sarah L. Haggas, Yasutaka Hayasaka, Kenji Hirata, Benjamin C. Horner-Johnson, Kevin W. Mandernack, Francine M. G. McCarthy, Ralph Moberly, Masashi Mochizuki, Rikke Ohlenschlaeger Pedersen, Ali R. M. Salimullah, Masanao Shinohara and Carl-Dietrich Werner; Ocean Drilling Program, Leg 191, Shipboard Scientific Party, College Station, TX. Proceedings of the Ocean Drilling Program, Scientific Results (CD ROM), Vol.191, 21p. Publisher: Texas A&M University, Ocean Drilling Program, College Station, TX, United States. ISSN: 1096-2514
Note: In English. Includes appendices; available only on CD-ROM in PDF format and on the Web in PDF or HTML. 7 refs.CD-ROM format, ISSN 1096-2514; WWW format, ISSN 1096-7451; illus., incl. 2 tables
Summary: The Multi-Sensor Spectral Gamma Ray Tool (MGT) developed for the Ocean Drilling Program (ODP) utilizes common-depth stacked data from an array of small detectors to improve the vertical resolution of natural gamma ray logs. The first field results using the MGT were obtained at ODP Site 1179 in the northwest Pacific, which penetrated clay and ash-bearing marine ooze. Data were processed postcruise to correct for borehole size effects and logging speed variations, and the tool was recalibrated at a commercial testing facility. The standard Schlumberger gamma ray tool (HNGS) was also run over the same depth interval at this site. Comparisons of the MGT and HNGS logs agree closely in total measured gamma ray counts (gAPI), although the vertical resolution of the MGT was observed to be significantly greater than the HNGS. Estimates of elemental concentrations from both tools agree well for K but differ for U and Th. Based on this comparison, the HNGS underestimates U concentration by ∼1-2 ppm and the MGT underestimates Th concentration by 70%-80%. Enlarged borehole size (>42 cm) and the low gamma ray levels in these sediments, as well as the intrinsic differences in detector geometry and gamma ray processing methods, may explain the observed differences in U and Th estimates. The MGT log provides the enhanced vertical resolution critical to resolve the geochemical signature of thin beds and high-frequency periodicity in complex stratigraphic sequences.
Year of Publication: 2003
Research Program: ODP Ocean Drilling Program
Key Words: 20 Geophysics, Applied; Accuracy; Common-depth-point method; Downhole methods; Gamma-ray methods; Geochemistry; Geophysical methods; Instruments; Leg 191; North Pacific; Northwest Pacific; ODP Site 1179; Ocean Drilling Program; Ocean floors; Pacific Ocean; Reflection methods; Seismic methods; Shatsky Rise; Well logs; Well-logging; West Pacific
Coordinates: N410400 N410500 E1595800 E1595700
Record ID: 2005072229
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