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University of California Publications. [Geology 



tion of the surface rock, and the evident impossibility of any 

 great volume of snow occurring here, all render this conception 

 highly improbable. Where the canon is flaring in cross-section, 

 with wide bottom, the small stream is cutting in talus from the 

 bounding scarps, quite similarly to the creek in Kings Canon. 

 This material finds its way to the bottom faster than the creek is 

 able to carry it below. But there are other peculiarities to this 

 longitudinal canon that, most unfortunately, the map fails to 

 show. The canon is clearly divisible into two very dissimilar 

 parts. The nature of the upper portion has been briefly dis- 

 cussed. The map shows the upper creek as draining southward 

 to Spooner Valley; the fact is that it does no such thing, but at 

 a line of east-west faulting at the schist-granite contact, turns 

 westward and flows through a narrow rock gorge into Lake Tahoe. 

 The idea of stream capture at once suggests itself. The other 

 accessory facts, as far as they have been determined, are as fol- 

 lows. The creek flowing westward, whose headwaters were at 

 some time extended sufficiently to capture the drainage in the 

 north-south canon, is normally a small wet-weather stream with 

 no drainage basin beyond a few acres in area. The north-south 

 creek at the point of sharp turn to the west, carries considerable 

 water at all seasons, being fed by perpetual springs at the head of 

 the canon. The small gorge through which this creek leaves the 

 main canon is sharp-cut and rocky, and apparently not due to 

 stream cutting. Further than this, were the small gorge to the 

 west stream-cut it must have been made by the larger creek, for 

 the small wet-weather stream is unable to do such work. This 

 would presuppose that originally there was no gorge but at most 

 a shallow notch in the ridge at this point. If such a condition 

 obtained, the larger creek would be forced to flow on down the 

 longitudinal canon. Hence the peculiar turn of the large creek 

 to the west cannot be due to stream capture and must be of struc- 

 tural origin. This hypothesis is born out by other facts. The 

 deep steep-walled canon through which the creek flows westward 

 possesses what is in this region the most common characteristic, 

 a fault canon. The stream at fairly high grade is trenching in 

 the granite sand carried clown from the steep walls, similarly 

 to Kings Canon Creek; the rock disintegration is proceeding 



