Bulletin of the Geological Society of America . rn Canada 690 Eastern United States 691 Northern New York 691 New England 691 Appalachian-Piedmont region 692 Minnesota, Wisconsin, and Michigan 692 Missouri and South Dakota 693 Texas 693 Arizona and New Mexico 694 Nevada and Utah 694 Colorado 695 Wyoming 696 Montana and Idaho 697 Conclusions regarding the Cordilleran region 697 General conclusions 698 Discussion 699 Introduction Any serious attempt to decipher the pre-Cambrian paleogeography ofthe continents, even if only in broad outline, should be commended. Ai\ 1 Manuscript received by the S
Bulletin of the Geological Society of America . rn Canada 690 Eastern United States 691 Northern New York 691 New England 691 Appalachian-Piedmont region 692 Minnesota, Wisconsin, and Michigan 692 Missouri and South Dakota 693 Texas 693 Arizona and New Mexico 694 Nevada and Utah 694 Colorado 695 Wyoming 696 Montana and Idaho 697 Conclusions regarding the Cordilleran region 697 General conclusions 698 Discussion 699 Introduction Any serious attempt to decipher the pre-Cambrian paleogeography ofthe continents, even if only in broad outline, should be commended. Ai\ 1 Manuscript received by the Secretary of the Society February 26, 1923. (679) 680 W. J. MILLER PRE-CAMBRIAN FOLDING IN NORTH AMERICA elaborate effort of this kind has very recently been made^ by E. Ruede-mann, whose paper is valuable mainly because of its highly suggestivefeatures. In it he ^Ventures to suggest some possible fundamentals ofpre-Cambrian paleogeography/^ It is not too much to say that Ruede-mann has opened up a new and important field of geological Figure 1.—Map of North America Showing, by the short, heavy lines, observed strikes of pre-Cambrian folding andfoliation and, by the long, curved, dotted lines, the pre-Cambrian structural trend-linesadvocated by Ruedemann. The short, broken lines indicate strikes of pre-Cambrianrocks developed mainly or wholly in post-Cambrian time. The present purpose is to confine attention to one very importantaspect of the subject, in which the writer has been interested for someyears, and this in its application to North America only. This aspect ofthe subject is the folding and foliation of pre-Cambrian age, with special 2 R. Ruedemann : N. Y. State Museum Bulletin 240, 1922, pp. 67-152. GENERAL CONSIDERATIONS 681 reference to their trend-lines. This is a fundamental consideration inEuedemanns paper, and in his summary regarding the principal linesof pre-Cambrian folding in North. America he says: The northeast of North America, including Greenl
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectgeology, bookyear1890
