Vol. 6] Beid: The Geomorphogeny of the Sierra Nevada. 123 



faster than the stream erosion. This crumbling of granodiorite ap- 

 pears to be due, as in the other cases cited, to the great fracturing 

 along the fault-planes. However, the presence of the fault is 

 actually demonstrated stratigraphically by the position of the 

 schist area on the granodiorite. The crust block which carries 

 the metamorphic rock has been dropped relatively to the northern 

 area. 



Below the point where the creek turns westward and leaves 

 the main north-south canon, the bottom of the canon changes 

 abruptly from the wide, flaring portion above. The smooth open 

 curves of the upper cross-section give place to sharp angles and 

 constricted cross-section, and the fine rock debris to large blocks 

 of granite. The creek which flows in the lower cahonus cutting the 

 solid rock at a high gradient. The fault-line in this lower portion 

 is further emphasized by the stratigraphic evidence of the sunken 

 schist block. A question arises concerning the relative ages of 

 the longitudinal and cross-faults at this point, and whether or 

 not it is possible to determine them. We are confronted at once 

 with a seeming discrepancy in the facts — a fault which at once 

 has caused a downthrow of the schist block and dammed the 

 creek, so as to produce an abrupt change in the drainage line. 

 In the explanation of this paradox some idea of relative ages of 

 the faults can be gained. Obviously the large north-south canon 

 is the oldest physiographic feature that is due to longitudinal 

 faulting movements. Also, the small schist area north of Spooners 

 forms the west wall of the lower portion of this north-south fault 

 canon and was therefore concerned with the first movements. 

 But it is clearly a drown-dropped block, proved by the compara- 

 tively low elevations both of the granite-schist contact plane and 

 of the plateau remnants. It is therefore safe to conclude that 

 the schist block must have been bounded on north and south 

 by east-west cross-faults at the time of the formation of the north- 

 south canon. This makes some east-west faulting of same age as 

 the main longitudinal motion. But, the lower canon shows evi- 

 dence of slight elevation of the schist block subsequent to the 

 formation of the first fault features. From this, a later period 

 of east-west faulting, with secondary north-south faulting, is in- 

 ferred. This conclusion in regard to relative ages of faults is 



