Lateral continuity of basement seismic reflections in 15 Ma ultrafast-spreading crust at ODP Site 1256

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doi: 10.1007/s11001-011-9122-4
Author(s): Nag, Sreeja; Swift, Stephen A.
Author Affiliation(s): Primary:
Massachusetts Institute of Technology, Engineering Systems Division, Cambridge, MA, United States
Woods Hole Oceanographic Institution, United States
Volume Title: Marine Geophysical Research
Source: Marine Geophysical Research, 32(3), p.429-439. Publisher: Springer, Dordrecht, Netherlands. ISSN: 0025-3235 CODEN: MGYRA7
Note: In English. 19 refs.
Summary: The Ocean Drilling Program (ODP) initiated drilling at Site 1256D in the Guatemala Basin, about 1,000 km off the East Pacific Rise to penetrate plutonic rocks, anticipated to be relatively shallow in this region, formed at an ultra-fast spreading rate. IODP Expedition E312 successfully drilled into gabbros at ≈1,150 m in basement. Multi-channel seismic traces show weak laterally coherent sub-basement reflections at borehole depths. Synthetic reflectivity seismograms were computed using a Ricker wavelet and impedance profiles from borehole sonic logs. These seismograms show significant sub-basement amplitude peaks. A zero-offset vertical seismic profile, shot on E312, was processed to investigate the authenticity of these reflections and their relationship to borehole geology. A dual scheme of the median filtering and F-K dip filtering was used. Tests with synthetic seismograms indicate the approach is effective at reasonable SNR levels. Downgoing energy is clearly identified but negligible upgoing energy is visible over random noise. These results indicate that lava flows and igneous contacts in upper ocean crust have significant topography on lateral scales less than the Fresnel Zone (300 m) due to igneous and tectonic processes. Copyright 2011 Springer Science+Business Media B.V.
Year of Publication: 2011
Research Program: IODP Integrated Ocean Drilling Program
ODP Ocean Drilling Program
Key Words: 07 Marine Geology and Oceanography; 20 Geophysics, Applied; Basement; Cenozoic; Data processing; East Pacific; East Pacific Rise; Equatorial Pacific; Expedition 312; Expeditions 309/312; Filters; Gabbros; Geophysical methods; Geophysical profiles; Geophysical surveys; Guatemala Basin; Igneous rocks; Integrated Ocean Drilling Program; Marine methods; Miocene; Neogene; North Pacific; Northeast Pacific; ODP Site 1256; Ocean Drilling Program; Pacific Ocean; Plutonic rocks; Sea-floor spreading; Seismic methods; Seismic profiles; Seismograms; Surveys; Synthetic seismograms; Tertiary; Vertical seismic profiles; Volcanic rocks
Coordinates: N064400 N064400 W0915600 W0915600
Record ID: 2017078684
Copyright Information: GeoRef, Copyright 2017 American Geosciences Institute. Reference includes data from Geoline, Bundesanstalt fur Geowissenschaften und Rohstoffe, Hanover, Germany