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Confusing Seismic Data From The Deep Continental Crust

Seismic exploration of the deep continental crust seems to indicate that huge sheets of crystalline rock have been pushed over sedimentary strata. The crystalline sheets, perhaps kilometers in thickness, were forcibly shoved hundreds of kilometers over sedimentary deposits during continental collisions -- so the theory goes. One such crystalline sheet is under the Southern Appalachians. Seismic data say it is about 10 kilometers thick and was pushed westward some 225 kilometers. If it seems intuitively impossible for such a thin sheet to remain intact during 225kilometers of shoving over other rocks, consider a similar sheet in the Basin and Range province of Utah. This sheet was pulled down an inclined fault without coming apart!

These sliding sheets with remarkable structural integrities are required to explain what geophysicists see in the seismic reflections; namely, transparent zones of crystalline rock sitting on top of rocks that return strong reflections typical of layered sedimentary strata. However, one such situation in Arizona was explored with a drill bit. When the upper crystalline layer was penetrated, the drill found only more crystalline rocks, nothing sedimentary. In fact, the crystalline rock was not layered and was homogeneous. Thus, the source of the misleading seismic reflections is unknown.

(Kerr, Richard A.; "Continental Drilling Heading Deeper," Science, 224:1418, 1984. Also: Anonymous; "Probing the Deep Con-tinental Crust," Science, 225:492, 1984)

Comment. So-called "low-angle thrust faulting is often invoked to explain situations where large areas of older sedi-mentary rocks overlie younger rocks. More on these thrust faults may be found under ESR3 in Inner Earth. For ordering information, visit: here.

From Science Frontiers #35, SEP-OCT 1984. 1984-2000 William R. Corliss

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  • "A sourcebook of unexplained phenomena is therefore a valuable addition to a collection of scientific literature. William R. Corliss has provided this in the past with his source books of scientific anomalies in several subjects, and now he has provided it for astronomy. He has done an excellent job of collecting and editing a large amount of material, taken in part from scientific journals and in part from scientific reporting in the popular or semi-scientific press." -- "The Mysterious Universe: A Handbook of Astronomical Anomalies", reviwed by Thomas Gold, Cornell University, in Icarus, vol.41, 1980

  • "An interesting, systematic presentation of unusual weather [..] This book is recommended for a general audience" --"Corliss, William R., Tornados, Dark Days, Anomalous Precipitation, and Related Weather Phenomena, Sourcebook Project, 1983.", revieweed in Choice, September 1983
  • "..the science is necessarily somewhat speculative, but Corliss's symthesis is based on reputable sources." -- "Corliss, William R. (Compiler). Lightning, Auroras, Nocturnal Lights, and Related Luminous Phenomena" reviwed by Joseph M. Moran, Univ. of Wisconsin in Science Books and Films, Sep/Oct 1983

  • "Before opening the book, I set certain standards that a volume which treads into dangerous grounds grounds like this must meet. The author scrupulously met, or even exceeded those standards. Each phenomenon is exhaustively documented, with references to scientific journals [..] and extensive quotations" -- "Book Review: The moon and planets: a catalog of astronomical anomalies", The Sourcebook Project, 1985., Corliss, W. R., Journal of the Royal Astronomical Society of Canada, Vol. 81, no. 1 (1987), p. 24., 02/1987