Abstract
THE igneous oceanic crust is typically thought of as comprising two layers: an upper crust ('seismic layer 2') characterized by a rapid increase in seismic velocity with depth, and a thicker lower crust ('seismic layer 3') which is distinguished from layer 2 by both a higher P-wave velocity (6.69 ± 0.26 km s -l) and a much smaller vertical velocity gradient (<1 km s-1 km-1)1–3. A direct correlation has never been established between this seismic layering and the in situ lithological and physical properties of oceanic crust. The transition between seismic layers 2 and 3 has been variously interpreted as a change in igneous rock texture from doleritic sheeted dykes to gabbro4,5, an increase in metamorphic grade from greenschist- to amphibolite-facies rocks2,6–9, or a change in bulk crustal porosity with depth2,10. We have re-examined available seismic refraction data from around Hole504B, the deepest (>1.8 km) continuous hole drilled into the oceanic crust11–13, and find that at this location the seismic layer 2/3 boundary lies within the sheeted-dyke complex, where it is associated with gradual downhole changes in crustal porosity and alteration, not a litho-logical transition from sheeted dykes to gabbro.
This is a preview of subscription content, access via your institution
Access options
Subscribe to this journal
Receive 51 print issues and online access
$199.00 per year
only $3.90 per issue
Buy this article
- Purchase on Springer Link
- Instant access to full article PDF
Prices may be subject to local taxes which are calculated during checkout
Similar content being viewed by others
References
Raitt, R. W. in The Sea Vol. 3 (ed. Hill, M. N.) 85–102 (Wiley-lnterscience, New York, 1963).
Spudich, P. & Orcutt, J. A. Rev. Geophys. Space Phys. 18, 627–645 (1980).
White, R. S., McKenzie, D. & O'Nions, R. K. J. geophys. Res. 97, 19683–19716 (1992).
Fox, P. J., Schreiber, E. & Peterson, J. J. J. geophys. Res. 78, 5155–5172 (1973).
Fox, P. J. & Stroup, J. B. in Then Sea (ed. Emiliani, C.) 119–218 (Wiley & Sons, New York, 1981).
Christensen, N. I. Geol. Soc. Am. Bull. 81, 905–908 (1970).
Peterson, J. J., Fox, P. J. & Schreiber, E. Nature 247, 194–196 (1974).
Christensen, N. I. & Salisbury, M. H. Rev. Geophys. Space Phys. 13, 57–86 (1975).
Salisbury, M. H. & Christensen, N. I. J. geophys. Res. 83, 805–817 (1978).
Lort, J. M. & Matthews, D. H. J. R. astr. Soc. 27, 383–392 (1972).
Becker, K. et al. Init. Rep. ODP Leg 111 (Part A) 35–251 (1988).
Dick, H. J. B. et al. Init. Rep. ODP Leg 140 37–200 (1992).
Alt, J. C. et al. Init. Rep. ODP Leg 148 27–121 (1993).
Becker, K. et al. Rev. Geophys. 27, 79–102 (1989).
Hobart, M. A., Langseth, M. G. & Anderson, R. N. Init. Rep. DSDP Leg 83 379–399 (1985).
Collins, J. A., Purdy, M. G. & Brocher, T. M. J. geophys. Res. 94, 9283–9302 (1989).
Zehnder-Mutter, C. JOI/USSAC Newsletter 4 (1992).
Stephen, R. A. & Harding, A. J. J. geophys. Res. 88, 8289–8298 (1983).
Little, S. A. & Stephen, R. A. Init. Rep. DSDP Leg 83 517–528 (1985).
Collins, J. A., Brocher, T. M. & Purdy, G. M. Proc. ODP Sci. Res. Leg 111 177–191 (1989).
Shor, G. G. Jr, Menard, H. W. & Raitt, R. W. in The Sea Vol. 4 (ed. Maxwell, A. E.) 3–27 (Wiley-lnterscience, New York, 1970).
Laverne, C. et al. Proc. ODP, Sci. Res. Leg 140 (in the press).
Casey, J. F., Dewey, J. F., Fox, P. J., Karson, J. A. & Rosencrantz, E. in The Sea Vol. 7 (ed. Emiliani, C.) 305–338 (Wiley-lnterscience, New York, 1981).
Becker, K. et al. Nature 300, 594–598 (1982).
Carlson, R. L. & Herrick, C. N. J. geophys. Res. 95, 9153–9170 (1990).
Christensen, N. I. Tectonophysics 47, 131–157 (1978).
Christensen, N. I. & Smewing, J. D. J. geophys. Res. 86, 2545–2556 (1981).
Swift, S. & Stephen, R. Geophys. Res. Lett. 19, 1871–1874 (1992).
Detrick, R. S. et al. Nature 326, 35–41 (1987).
Detrick, R. S. et al. Science 259, 499–503 (1993).
Morton, J. L., Sleep, N. H., Normark, W. R. & Tompkins, D. H. J. geophys. Res. 92, 11315–11326 (1987).
Collier, J. & Sinha, M. Nature 346, 646–648 (1990).
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Detrick, R., Collins, J., Stephen, R. et al. In situ evidence for the nature of the seismic layer 2/3 boundary in oceanic crust. Nature 370, 288–290 (1994). https://doi.org/10.1038/370288a0
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1038/370288a0
This article is cited by
-
Middle-lower continental crust exhumed at the distal edges of volcanic passive margins
Communications Earth & Environment (2022)
-
Uppermost crustal structure across the eastern Lau spreading center from P-to-S converted waves
Marine Geophysical Research (2020)
Comments
By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.