CONTROLLED FRACTURE FIELDS OF NORTH AMERICA 



153 



brought out in 1904/* A subequal spacing of these lineaments was also 

 indicated, the large interval of the northeast-southwest series being 125 

 miles, that of the northwest-southeast series 

 about 75 miles, and that of the north-south 

 series about 40 miles. Patterned drainage 

 from western Connecticut, in accordance 

 with these directions, is brought out in fig- 

 ure 37. 



Similar examples of patterned and 

 oriented fracture fields have been found 

 also in western sections of the country. 

 Of the basin ranges of Nevada and Cali- 

 fornia, Spurr says:*^ 



"The chief faults belong to the north and 

 south and east and west systems. There are 

 also diagonal ones running northeast and south- 

 west, and in each of the systems they may have 

 a very great displacement." 



The clays of lakes Bonneville*^ and La- 

 hontan*" are intersected by an elaborate 

 joint system of essentially the same orienta- 

 tion. 



In the Yellowstone National Park, Id- 

 dings has described a network of faults 

 which have produced a "fracture valley sys- 

 tem" in which the dominant directions are 

 northeast - southwest, northwest - southeast, 

 north-south, and east-west.*^ From the 

 Sierra Nevadas, Lawson has published 

 a map which discloses a striking orientation of faults and drainage lines 

 in harmony with the quadruple set of lineaments found in the other dis- 

 tricts (see figure 38).*® 



3 miles 



Figure 27. — Patterned Drainage 

 of the Shepang Valley, Connec- 

 ticut. 



(Hobbs, U. S. Geological Survey) 



" W. H. Hobbs : Lineaments of the Atlantic Border region. Bulletin of the Geologi- 

 cal Society of America, vol. 15, pp. 483-506, pis. 45-47. 



*^ J. E. Spurr : Origin and structure of the Basin ranges. Bulletin of the Geological 

 Society of America, vol. 12, 1901, p. 241. 



"G. K. Gilbert: Post-glacial joints. American Journal of Science (3), vol. 23, 1882, 

 pp. 25-27. Also Monograph T, U. S. Geological Survey, 1890, pp. 211-213. 



*'' I. C. Russell : Geological history of Lake Lahontan. Monograph XI, U. S. Geo- 

 logical Survey, 1885, pp. 162-163. 



*8 J. P. Iddings : A fracture valley system. Journal of Geology, vol. 12, 1904, pp. 94- 

 105, plate. 



*" A. C. liawson : The geomorphogeny of the Tehachapi Valley system. Bulletin of 

 the Department of Geology of the University of California, vol. 4, No. 19, pp. 431-462, 

 pi. 42. 



