In situ acoustic properties of pelagic carbonate sediments on the Ontong Java Plateau

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doi: 10.1029/JB094iB04p04025
Author(s): Fulthorpe, Craig Stephen; Schlanger, Seymour O.; Jarrard, Richard D.
Author Affiliation(s): Primary:
Northwest. Univ., Dep. Geol. Sci., Evanston, IL, United States
Other:
Lamont-Doherty Geol. Obs., United States
Volume Title: Journal of Geophysical Research
Source: Journal of Geophysical Research, 94(B4), p.4025-4032. Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 0148-0227
Note: In English. 29 refs.; illus. incl. sketch map
Summary: The Ontong Java Plateau, with its thick, capping sequence of Cretaceous and Cenozoic pure pelagic carbonate sediments, forms an ideal setting for the study of the acoustic properties of this lithology on an oceanic rise. Borehole logs, recorded on Deep Sea Drilling Project leg 89 at site 586, provided detailed data on in situ acoustic properties of Pleistocene to early Miocene sediments to a depth of 623 m below seafloor. Comparison of these logging results and the sonobuoy-based results of Johnson et al. (1978) with previous laboratory measurements from the Ontong Java Plateau shows that velocity/depth functions determined from the logging and sonobuoy methods are concordant but diverge significantly from functions derived from laboratory measurements. Log densities and compressional velocities exceed those measured by laboratory techniques; the density discrepancy is strongly influenced by laboratory method. The differences between log and laboratory compressional velocities are greater than and extend to greater depths than those between densities. These differences can be attributed to reductions in the frame bulk modulus and dynamic rigidity, caused by the removal of overburden pressure in the absence of significant porosity rebound. Agreement of site 586 log velocities with velocities derived from the earlier sonobuoy measurements across the plateau argues for the interpretation that both methods measure in situ values. The disagreement between the site 586 log results and the sonobuoy results with both the empirical velocity/depth function of Carlson et al. (1986) and the empirical velocity/porosity function of Raymer et al. (1980) supports the conclusion that pelagic carbonate sediments on oceanic plateaus and rises have unique acoustic properties, primarily arising from the presence of intraparticle porosity, and should not be grouped with other oceanic lithologies in acoustic modeling studies.
Year of Publication: 1989
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
Key Words: 07 Marine Geology and Oceanography; 20 Geophysics, Applied; Acoustical logging; Acoustical properties; Carbonate sediments; Cenozoic; DSDP Site 289; DSDP Site 586; Deep Sea Drilling Project; IPOD; In situ; Interpretation; Leg 30; Leg 89; Marine environment; Marine sediments; Neogene; Oceanography; Ontong Java Plateau; Pacific Ocean; Pelagic environment; Pleistocene; Quaternary; Sediments; Tertiary; Well-logging; West Pacific
Coordinates: S020000 N020000 E1600000 E1500000
Record ID: 1989048497
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