CONCERNING THE PROCESS OF THRUST FAULTING 



TERENCE T. QUIRKE 



University of Illinois 



The following paper is offered as a contribution to the studies 

 of low-angle faulting which have been led by the researches and 

 teaching of Professor R. T. ChamberHn. , 



A comparison of this paper with previous publications, espe- 

 cially "Low-Angle Faulting," by R. T. Chamberlin and W. Z. 

 Miller,^ will show that the writer has followed ChamberHn in large 

 measure. Most of the material here presented has really been 

 anticipated in the article referred to, but a different manner of 

 approach on some phases of the study is attempted, and the 

 possibility is suggested that there may be a closer relationship 

 between low- and high-angle thrust faults than is commonly 

 accepted. 



In 1910 ChamberHn^ published his paper on the structure of 

 the Appalachian Mountains in which he showed reason to believe 

 that the part of the crust affected by deformation is a shallow, 

 wedge-shaped mass about thirty miles deep and about nine hundred 

 miles long. WilHs,^ upon independent but similar arguments, sug- 

 gested that the depth of the mass deformed in the uplift of the 

 Cascades lies between thirty-seven and one-half and fifteen hun- 

 dred miles. 



So far as the writer knows, these conclusions have been accepted 

 as sound, in spite of the fact that they appear to be fundamentally 

 different from the prevalent notion that mountain folding is rela- 

 tively shallow and that the deformable crust of the earth is of the 



' Jo2<r. Geol., XXVI (1918), 1-44. 



^ R. T. Chamberlin, "Appalachian Folds of Central Pennsylvania," Jour. Geol., 

 XVIII (1910), 228-51. 



^ Bailey Willis, U.S. Geol. Siirv., Prof. Paper No. ig (1903), p. 97. 



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