Lithostratigraphic interpretation of volcaniclastic sequences from Shatsky Rise using downhole measurements

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Author(s): Iturrino, G. J.; Evans, Helen F.; Matsubara, N.
Author Affiliation(s): Primary:
Lamont-Doherty Earth Observatory, Borehole Research Group, Palisades, NY, United States
Ibaraki University, Japan
Volume Title: AGU 2011 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2011; American Geophysical Union 2011 fall meeting, San Francisco, CA, Dec. 5-9, 2011. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: IODP Expedition 324 drilled five sites across the Shatsky Rise to test plume and plate models of ocean plateau formation at Shatsky Rise in the northwest Pacific Ocean. Site U1348 is located on the north flank of Tamu Massif. The target for drilling was the upper part of a basement high where sediments are thin. Hole U1348A was drilled to 324.1 m below the seafloor at the site, with predominantly hyaloclastic material was being encountered after passing through ∼200 m of Lower Cretaceous chert, chalk, and bioclastic sandstones containing some clasts of volcaniclastic origin. Downhole logging data obtained from Hole U1348A included natural and spectral gamma ray, density, photoelectric factor, compressional-wave velocity, and electrical resistivity measurements from three depths of investigation. Interpretations of gamma ray and electrical resistivity downhole logs were used to identify a total of 14 logging units in the open borehole section of Hole U1348A, five in the sedimentary sequences, and nine in the volcaniclastic section. Electrical resistivity measurements show distinctive higher resistivity zones that likely represent less altered intervals, interspersed with low resistivity zones that mark sediment interbeds and more altered sequences. Natural gamma-ray measurements show several intervals of higher readings that indicate interbedded sediments and higher alteration. These intervals also display higher potassium, uranium, and thorium values. Formation MicroScanner (FMS) images show zones with distinct layering, dipping beds, and vesicular or brecciated intervals. Structural analyses of dipping beds show high angle features and contacts at the bottom of the drilled sequence, which are striking northeast-southwest and dipping mostly 20-30° to the southeast.
Year of Publication: 2011
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; 18 Geophysics, Solid-Earth; Breccia; Carbonate rocks; Chalk; Chemically precipitated rocks; Chert; Clastic rocks; Cretaceous; Expedition 324; IODP Site U1348; Integrated Ocean Drilling Program; Lithostratigraphy; Lower Cretaceous; Mantle; Mantle plumes; Measurement; Mesozoic; North Pacific; Northwest Pacific; Ocean floors; Pacific Ocean; Plate tectonics; Resistivity; Sandstone; Sedimentary rocks; Sedimentation; Sediments; Shatsky Rise; Tamu Massif; Volcaniclastics; West Pacific
Record ID: 2017006588
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data supplied by, and/or abstract, Copyright, American Geophysical Union, Washington, DC, United States

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