Whole-Lithosphere Normal Simple Shear: An Interpretation of Deep-Reflection Profiles in Great Britain

  1. Muawia Barazangi and
  2. Larry Brown
  1. Brian Wernicke

Published Online: 15 MAR 2013

DOI: 10.1029/GD014p0331

Reflection Seismology: The Continental Crust

Reflection Seismology: The Continental Crust

How to Cite

Wernicke, B. (1986) Whole-Lithosphere Normal Simple Shear: An Interpretation of Deep-Reflection Profiles in Great Britain, in Reflection Seismology: The Continental Crust (eds M. Barazangi and L. Brown), American Geophysical Union, Washington, D. C.. doi: 10.1029/GD014p0331

Author Information

  1. Department of Geological Sciences, Harvard University

Publication History

  1. Published Online: 15 MAR 2013
  2. Published Print: 1 JAN 1986

Book Series:

  1. Geodynamics Series

ISBN Information

Print ISBN: 9780875905143

Online ISBN: 9781118670118

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Keywords:

  • Earth—Crust—Congresses;
  • Continents—Congresses;
  • Seismic reflection method—Congresses

Summary

Marine deep-seismic reflection profiles from the British Isles acquired by the British Institutions' Seismic Reflection Profiling Syndicate (BIRPS) provide some of the best images to date of the deep structure of a zone of intracontinental extension. Simple quantitative considerations of finite strain indicate that the reflection geometry on the eastern half of the MOIST profile is consistent with the concept that large, low-angle normal faults persist as single zones of displacement through the entire lithosphere. It is proposed that the lower crust absorbs displacement by the formation of a foliation parallel to the maximum elongation direction within finite-width normal shear zones. In contrast, both up-dip and down-dip in stronger or more brittle layers, the shear zones not only narrow, causing foliation to become aligned with their boundaries, but they also absorb strain via a foliation comprised of discrete, boundary-parallel slip surfaces. Such a geometry of through-going zones of displacement predicts non-alignment of lower crustal reflections with those in the mantle and upper crust within the same displacement zone. This model runs counter to current interpretations of deep reflection data that ascribe a more fundamental role to rheological stratification for the localization and development of zones of displacement in the lithosphere.