Rock magnetism of the diapir sites (sites 991, 992, 993, and 996), Carolina Rise and Blake Ridge

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doi: 10.2973/odp.proc.sr.164.234.2000
Author(s): Musgrave, Robert J.; Hiroki, Yoshihisa
Ocean Drilling Program, Leg 164, Shipboard Scientific Party, College Station, TX
Author Affiliation(s): Primary:
La Trobe University, Department of Earth Sciences, Bundoora, Victoria, Australia
Other:
University of Tokyo, Japan
Ocean Drilling Program, United States
U. S. Geological Survey, United States
University of Texas at Arlington, United States
University of Michigan, United States
Agder College, Norway
University of Bristol, United Kingdom
McGill University, Canada
Osaka Kyoiku University, Japan
Woods Hole Oceanographic Institution, United States
Lamont-Doherty Earth Observatory, United States
Osservatorio Geofisico-Sperimentale, Italy
La Trobe University, Australia
GEOMAR, Federal Republic of Germany
Hokkaido University, Japan
Université Pierre et Marie Curie, France
Georgia Institute of Technology, United States
Geological Survey of Japan, Japan
CREGU BP 23, France
Federal Institute for Geosciences, Federal Republic of Germany
Naval Research Laboratory, United States
Volume Title: Proceedings of the Ocean Drilling Program; volume 164; scientific results; gas hydrate sampling on the Blake Ridge and Carolina Rise; covering Leg 164 of the cruises of the drilling vessel JOIDES Resolution, Halifax, Nova Scotia, to Miami, Florida, sites 991-997, 31 October-19 December 1995
Volume Author(s): Paull, Charles K.; Matsumoto, Ryo; Wallace, Paul J.; Black, Nancy R.; Borowski, Walter S.; Collett, Timothy S.; Damuth, John E.; Dickens, Gerald R.; Egeberg, Per Kristian; Goodman, Kim; Hesse, Reinhard F.; Hiroki, Yoshihisa; Holbrook, W. Steven; Hoskins, Hartley; Ladd, John; Lodolo, Emanuele; Lorenson, Thomas D.; Musgrave, Robert J.; Naehr, Thomas H.; Okada, Hisatake; Pierre, Catherine; Ruppel, Carolyn D.; Satoh, Mikio; Thiéry, Régis; Watanabe, Yoshio; Wehner, Hermann; Winters, William J.; Wood, Warren T.; Miller, Christine M.; Reigel, Ruth
Source: Proceedings of the Ocean Drilling Program; volume 164; scientific results; gas hydrate sampling on the Blake Ridge and Carolina Rise; covering Leg 164 of the cruises of the drilling vessel JOIDES Resolution, Halifax, Nova Scotia, to Miami, Florida, sites 991-997, 31 October-19 December 1995, Charles K. Paull, Ryo Matsumoto, Paul J. Wallace, Nancy R. Black, Walter S. Borowski, Timothy S. Collett, John E. Damuth, Gerald R. Dickens, Per Kristian Egeberg, Kim Goodman, Reinhard F. Hesse, Yoshihisa Hiroki, W. Steven Holbrook, Hartley Hoskins, John Ladd, Emanuele Lodolo, Thomas D. Lorenson, Robert J. Musgrave, Thomas H. Naehr, Hisatake Okada, Catherine Pierre, Carolyn D. Ruppel, Mikio Satoh, Régis Thiéry, Yoshio Watanabe, Hermann Wehner, William J. Winters, Warren T. Wood, Christine M. Miller and Ruth Reigel; Ocean Drilling Program, Leg 164, Shipboard Scientific Party, College Station, TX. Proceedings of the Ocean Drilling Program, Scientific Results, Vol.164, p.401-409. Publisher: Texas A & M University, Ocean Drilling Program, College Station, TX, United States. ISSN: 0884-5891
Note: In English. 28 refs.; illus.
Summary: Magnetic diagenesis, involving a sequence of iron reduction steps resulting in initial authigenesis of magnetite and progressing through reduction to greigite and on to pyrite, can be traced in Leg 164 sites by downhole changes in susceptibility, the hysteresis parameter DJH, and coercivity spectra. An undisturbed reference site on the Blake Ridge (Site 995) shows an initial increase in susceptibility between 0 and 4 mbsf, consistent with authigenesis of fine-grained magnetite and greigite, followed by almost complete reduction to pyrite below 4 mbsf. Site 991 shows a similar pattern restricted to Unit I; Unit II, although it commences at only 2 mbsf, is thoroughly reduced, reflecting the removal of material in a slide prior to the deposition of Unit I. At Site 992 the authigenesis of magnetite in Unit I has a different character; it is dominated by single-domain magnetite, suggesting that the multiple remobilization and redeposition of Unit I sediments at this site may have encouraged the growth of slightly larger magnetite grains, perhaps by incorporation of additional sulfate in the redeposited sediments. Unit I sediments at Site 992 have never been exhaustively reduced, suggesting that they were not buried by more than about 4 m prior to remobilization. In contrast, the entire sequence at both Sites 993 and 996 are thoroughly reduced. At Site 993 this reflects the exhumation of the site, which was previously estimated by physical properties (shear strength) measurements to be 50-80 m. Site 996 has not been exhumed significantly; instead reduction here has proceeded extensively even near the seafloor because of the supply of methane along a fault.
Year of Publication: 2000
Research Program: ODP Ocean Drilling Program
Key Words: 03 Geochronology; Atlantic Ocean; Authigenic minerals; Blake-Bahama Outer Ridge; Carolina Rise; Cenozoic; Dates; Diapirs; Exhumation; Leg 164; Magnetic properties; Magnetic susceptibility; Magnetite; Marine sediments; Neogene; North Atlantic; ODP Site 991; ODP Site 992; ODP Site 993; ODP Site 996; Ocean Drilling Program; Oxides; Paleomagnetism; Quaternary; Relative age; Sediments; Tertiary
Coordinates: N325832 N325832 W0755458 W0755458
N322938 N322938 W0761127 W0761127
N325746 N325746 W0755341 W0755341
N325901 N325901 W0755548 W0755548
Record ID: 2001025833
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