Laterally Persistent Seismic Characteristics of the Lower Crust: Examples from the Northern Appalachians

  1. Robert F. Mereu,
  2. Stephan Mueller and
  3. David M. Fountain
  1. Francois Marillier,
  2. Charlotte E. Keen and
  3. Glen S. Stockmal

Published Online: 9 APR 2013

DOI: 10.1029/GM051p0045

Properties and Processes of Earth's Lower Crust

Properties and Processes of Earth's Lower Crust

How to Cite

Marillier, F., Keen, C. E. and Stockmal, G. S. (1989) Laterally Persistent Seismic Characteristics of the Lower Crust: Examples from the Northern Appalachians, in Properties and Processes of Earth's Lower Crust (eds R. F. Mereu, S. Mueller and D. M. Fountain), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM051p0045

Author Information

  1. Geological Survey of Canada, Atlantic Geoscience Centre, Bedford Institute of Oceanography, P.O. Box 1006, Dartmouth, Nova Scotia, B2y 4A2, Canada

Publication History

  1. Published Online: 9 APR 2013
  2. Published Print: 1 JAN 1989

ISBN Information

Print ISBN: 9780875904566

Online ISBN: 9781118666388

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Keywords:

  • Earth—Crust—Congresses;
  • Geophysics—Congresses

Summary

Over 1600 km of deep seismic data were recently acquired to probe the crust and the upper mantle of the Appalachians in Canada. Although it is usually difficult to relate the surface expression of tectonic provinces to characteristic seismic signatures in the crust, our data show consistent seismic patterns in the lower crust, over distances of several hundreds of kilometres. These patterns enable us to identify three lower crustal blocks which underlie the orogen. In some places, boundaries between crustal blocks are identified by consistent differences in the seismic character of the Moho reflections. We suggest that one of these block boundaries (between the Central and Avalon crustal blocks) corresponds to a fault at the surface which has been identified as the Gander-Avalon terrane boundary.

High reflectivity of the lower crust and/or bright elongated Moho reflections are observed along some profiles where velocities higher than 7.0 km/s have been measured by earlier refraction studies. Although similar observations have been associated with extensional terranes by many authors, our data indicate that they can also be found in convergent environments.