New insights into deformation and fluid flow processes in the Nankai Trough accretionary prism; results of Ocean Drilling Program Leg 190

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doi: 10.1029/2001GC000166
Author(s): Moore, Gregory F.; Taira, Asahiko; Klaus, Adam; Becker, Luann; Boeckel, Babette; Cragg, Barry A.; Dean, Allison; Fergusson, Christopher L.; Henry, Pierre; Hirano, Satoshi; Hisamitsu, Toshio; Hunze, Sabine; Kastner, Miriam; Maltman, Alex J.; Morgan, Julia K.; Murakami, Yuki; Saffer, Demian M.; Sánchez-Gómez, Mario; Screaton, Elizabeth J.; Smith, David C.; Spivack, Arthur J.; Steurer, Joan; Tobin, Harold J.; Ujiie, Kohtaro; Underwood, Michael B.; Wilson, Moyra
Author Affiliation(s): Primary:
University of Hawaii at Manoa, Department of Geology and Geophysics, Honolulu, HI, United States
Other:
University of Tokyo, Japan
Ocean Drilling Program, United States
Universität Bremen, Federal Republic of Germany
University of Bristol, United Kingdom
Western Washington University, United States
University of Wollongong, Australia
École Normale Supérieure, France
Japan Marine Science and Technology, Japan
Geowissenschaftliche Gemeinschaftsaufgaben, Federal Republic of Germany
Scripps Institution of Oceanography, United States
University of Wales, United Kingdom
Rice University, United States
Hiroshima University, Japan
University of Wyoming, United States
Universidad de Jaén, Spain
University of Florida, United States
University of Rhode Island, United States
Unviersity of Missouri, United States
New Mexico Institute of Mining and Technology, United States
National Science Museum, Japan
University of Durham, United Kingdom
Volume Title: Geochemistry, Geophysics, Geosystems - G<sup>3</sup>
Source: Geochemistry, Geophysics, Geosystems - G>3`, 2(10). Publisher: American Geophysical Union and The Geochemical Society, United States. ISSN: 1525-2027
Note: In English. Accessed on Feb. 7, 2002; 22 p.. 41 refs.; illus., incl. strat. cols., sects., sketch maps
Summary: The Nankai Trough accretionary prism is considered an "end-member" prism accreting a coarse terrigenous sediment section in a setting with structural simplicity, unparalleled resolution by seismic and other geophysical techniques, and large historic earthquakes. It therefore has been the focus of Ocean Drilling Program (ODP) drilling to address several unresolved questions concerning accretionary processes and prism evolution. At six sites cored along two transects across the Nankai Trough accretionary prism during ODP Leg 190, lithostratigraphy and sediment diagenesis vary markedly. For the first time, reference sites at the seaward ends of the two transects defined the stratigraphic framework of the accreting/subducting Shikoku Basin sedimentary section. A thick section of Miocene turbidites and smectite-rich mudstone is present within the subducting section at the Ashizuri site. The turbidites and mudstones are absent in the correlative section at the Muroto site; variations in lithology, mineralogy, and hydrologic properties of the incoming sediments probably contribute to the difference in prism wedge taper between the two transects, while possibly controlling the seismic character of the active plate boundary. The decollement in both transects is localized within a common stratigraphic unit (∼5.9-7 Ma) within the lower Shikoku Basin facies. The decollement is also a major boundary for both physical and mechanical properties. A broad low-chloride pore water anomaly in the lower Shikoku Basin unit, first identified at Site 808, progressively decreases in magnitude from prism to basin along the Muroto Transect. Physical properties relationships, evidence for mineralogic changes in the sediments, and pore fluid chemistry suggest that the chloride anomaly results primarily from in situ diagenetic reactions in the sediments, possibly augmented by flow of freshened fluid from depth. New constraints on stratigraphy and age of units along more landward parts of the Muroto Transect have dramatically changed our ideas about the tectonic evolution of the prism in this area. Growth of the seaward-most part of the prism took place very rapidly, with 40 km of accretion within the past 2 Myr. This rate is at least 3 times greater than growth rates in a comparable prism.
Year of Publication: 2001
Research Program: ODP Ocean Drilling Program
Key Words: 07 Marine Geology and Oceanography; 16 Structural Geology; Accreting plate boundary; Accretionary wedges; Basins; Cenozoic; Clastic rocks; Continental margin; Cores; Decollement; Deformation; Geochemistry; Leg 190; Marine sediments; Mineral composition; Miocene; Mudstone; Nankai Trough; Neogene; North Pacific; Northwest Pacific; Ocean Drilling Program; Ocean floors; Pacific Ocean; Sedimentary basins; Sedimentary rocks; Sediments; Shikoku Basin; Subduction zones; Tectonics; Tertiary; Turbidite; West Pacific
Coordinates: N310000 N340000 E1370000 E1320000
Record ID: 2002018096
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