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.
This is a preview of subscription content, access via your institution.
Buy single article
Instant access to the full article PDF.
Tax calculation will be finalised during checkout.
Subscribe to journal
Immediate online access to all issues from 2019. Subscription will auto renew annually.
Tax calculation will be finalised during checkout.
Barckhausen U, Ranero CR, von Huene R, Cande SC, Roeser HA (2001) Revised tectonic boundaries in the Cocos Plate off Costa Rica: implications for the segmentation of the convergent margin and for plate tectonic models. J Geophys Res 106:19207–19220
Benn K, Nicolas A, Reuber I (1988) Mantle-crust transition zone and the origin of wehrlitic magmas: evidence from the Oman ophiolite. Tectonophysics 151:75–85
Detrick RS, Buhl P, Vera E, Mutter J, Orcutt JA, Madsen JJ, Brocher T (1987) Multi-channel seismic imaging of a crustal magma chamber along the East Pacific Rise. Nature 326:35–41
Hallenborg E et al (2003) Seismic structure of 15 Ma oceanic crust formed at ultrafast spreading East Pacific Rise: evidence for kilometer-scale fracturing from dipping reflectors. J Geophys Res 108(B11):2532. doi:10.1029/2003JB002400
Hardage BA (2000) Vertical seismic profiling: principles, 3rd edn. Elsevier Science Ltd., the Boulevard, Langford LanKidlington, Oxford OX5 1GB, UK
Harding AJ, Kent GM, Orcutt JA (1993) A multichannel seismic investigation of upper crustal structure at 9 N on the East Pacific Rise: implications for crustal accretion. J Geophys Res 98:13925–13944
Kennett BLN, Kerry NJ (1979) Seismic Waves in a stratified half-space. Geophys J R Astr Soc 57:557–583
Kent GM, Harding AJ, Orcutt JA (1990) Evidence for a smaller magma chamber beneath the East Pacific Rise at 9_300 N. Nature 344:650–653
Mallick S, Frazer LN (1987) Practical aspects of reflectivity modeling. Geophysics 52(10):1355–1364
Ranero CR, Reston TJ, Belykh I, Gnibidenko H (1997) Reflective oceanic crust formed at a fast-spreading center in the Pacific. Geology 25:499–502
Stephen RA et al (1985) Finite difference synthetic acoustic logs. Geophysics 50(10):1588–1609
Suprajitno M, Greenhaigh SA (1985) Separation of upgoing and downgoing waves in vertical seismic profiling by contour-slice filtering. Geophysics 50(6):950–962
Swift S, Reichow M, Tikku A, Tominaga M, Gilbert L (2008) Velocity structure of upper ocean crust at ocean drilling program site 1256. Geochem Geophys Geosyst 9:Q10O13. doi:10.1029/2008GC00218
Teagle DAH, Alt JC, Umino S, Miyashita S, Banerjee NR, Wilson DS (2006). The expedition 309/312 scientists. In: proceedings of IODP, 309/312: Washington, DC (Integrated ocean drilling program management international, Inc.). doi:10.2204/iodp.proc.309312.2006
Wilcock WSD, Solomon SC, Toomey DR (1995) Seismic attenuation structure of the East Pacific Rise near 9300 N. J Geophys Res 100:24147–24165
Wilson DS (1996) Fastest known spreading on the miocene cocos-pacific plate boundary. Geophys Res Lett 23:3003–3006
Wilson DS, Teagle DAH, Acton GD et al and Shipboard scientific party (2003) Site 1256. In: proceedings of ODP, Init. Repts., 206. Availiable from: ocean drilling program, Texas A&M University, College Station TX 77845-9547, USA
Wilson DS et al (2006) Drilling to gabbro in intact ocean crust. Science 312(5776):1016–1020. doi:10.1126/science.1126090
Yilmaz O (2001) Seismic data analysis—processing, inversion, and interpretation of seismic data. Soc Explor Geophys 1
We are extremely grateful to Dr. Ralph A. Stephen for spending hours of time discussing the various theories and research advancements in fields of my interest, eventually helping me choose this topic, Dr. J.A. Collins, Department of Geology and Geophysics, Woods Hole Oceanographic Institution for allowing us to use his synthetic seismogram reflectivity code and to the unknown reviewers who helped us significantly improve the quality of this manuscript.
About this article
Cite this article
Nag, S., Swift, S.A. Lateral continuity of basement seismic reflections in 15 Ma ultrafast-spreading crust at ODP Site 1256. Mar Geophys Res 32, 429–439 (2011). https://doi.org/10.1007/s11001-011-9122-4
- East pacific rise
- Vertical seismic profiling