Faults and Dykes; A Geological Study of the Witwatersrand (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1911 Excerpt: ...it becomes reasonably certain that a fault has been overturned by the tilting of the formation, it will be most convenient to refer its functions to the true horizontal and vertical planes, merely noting the reversal of the law of normalism. A further reason for distrusting the law of normal faulting as applied to a bedded formation is provided by the action of" slide-thrusts. It has previously been explained that these faults, in regard to their action upon the reef, are only distinguishable from other faults because their movement happens to be confined to a plane parallel to the plane of the reef. They have functions comparable to those of any other fault, and those functions, according to the author's definition, may be either normal or reversed. Yet it is clear that the dip of the slide-thrust cannot affect the direction of its movement in any way. If the country on the hanging-wall side of a slide thrust has been moved against the"dip of the formation, the fault will have reversed functions, and vice versa. Now, if the author's conception of the origin of a slide-thrust be correct, its movement has not been induced by the forces which are supposed to have caused the preponderance of normal faults, and the terms " normal " and "reversed" have no meaning when applied to slide-thrusts. In its incidence upon a fissure-vein in a bedded formation a slide-thrust will not generally be distinguishable from an ordinary fault; but in some cases the necessary evidence should be obtainable, and then, as in the case of a bedded reef, the fault might at once be labelled as a slide-thrust, and its normalism or otherwise need not then be considered. The question is not, however, as simple as that. There is every reason to ...