550 



KIRK BRYAN 



the basin rises above the alluvial plain and produces Lovejoy 

 Springs/ Examples of rock dams formed by intrusion of igneous 

 rock into alluvium have not yet been found. 



Fault dam springs arise where the free flow of ground water 

 through porous material is interfered with by faulting (Fig. 13 6?). 

 Fault zones become efficient barriers by the formation of gouge or 

 simply through disturbance and dislocation of the beds. Examples 



Fig. 17.— Map of the Niles cone, California, showing fault-dam springs due to 

 the Niles-Irvington fault. (After Clark.) 



of this class of spring have been found in the Big Smoky Valley, 

 Nevada, by Meinzer.^ The Niles-Irvington fault, in the Santa 

 Clara Valley, Cahfornia, beheads an alluvial fan (the Niles cone^), 

 as shown in Figure 17. On the side near the mountains the water 



^H. R. Johnson, "Water Resources of Antelope Valley, California," U.S. Geol. 

 Survey, Water-Supply Paper 278 (191 1), p. 52, Fig. 9. 



==0. E. Meinzer, "Geology and Water Resources of Big Smoky, Clayton, and 

 Alkalai Spring Valleys, Nevada," U.S. Geol. Survey, Water-Supply Paper 423 

 (1917), P- 90- 



3 W. O. Clarke, "Ground Water Resources of the Niles Cone and Adjacent Areas, 

 California," U.S. Geol. Survey, Water-Supply Paper 345 (1915), pp. 130-32, 150. 



