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University of California Publications. [Geology 



one of which has risen relatively to the other. If this section be 

 taken through Franktown, the position of the plateau remnants 

 brings out this structure prominently. The block to the west, 

 which here forms the main range crest, is bounded on both sides 

 by steep, unbroken scarps, hardly notched by stream erosion. 

 To the east of Little Valley, a slope rises to the crest of the fault- 

 block on that side, first gently and then steeply.- This east crest 

 descends to Washoe Valley over a gentler slope than the scarp 

 to the west. The lower fault-scarp, however, is not uniform. 

 Near Franktown a portion is very steep ; south of Franktown 

 Creek Canon the slope is comparatively low ; further south the 

 steepness again increases. As a physiographic unit, Little Val- 

 ley has clear and definite boundaries north and south, ending well 

 to the south of Slide Mountain. As a structural feature the val- 

 ley extends northward east of Slide Mountain at least as far as 

 the limits of the map. The low eastern crest is plainly to be 

 seen on the east flank of Slide Mountain. This is much more 

 impressive in the field than on the map. 



Longitudinally, Little Valley is divisible into three sharply 

 distinct parts : northern, middle and southern. The north por- 

 tion lies north of the forks of Franktown Creek ; the middle lies 

 between the forks and the sharp jog in the creek half a mile 

 south ; the south part embraces all the valley south of the jog just 

 noted. The reasons for this division are physiographic and struc- 

 tural, as will appear later; that there is also a reason of a dif- 

 ferent order is evident from the hypsometric discordance of the 

 several plateau remnants associated with the valley boundaries. 



The middle portion of Little Valley is the simplest, and will 

 first be described. The valley proper is flat-bottomed, deeply 

 alluviated, and nearly half a mile wide. To the west the valley 

 floor connects with the west fault-scarp by the gentle upward 

 slope of an alluvial apron. Above this the scarp rises as perfect 

 as if cut by a giant mason. To the west the valley floor first 

 rises A^ery gently to the foot of the slightly higher slopes leading 

 up to the summit of the east ridge. On the crest of this ridge is 

 a distinct remnant of the old plateau, which seems to have suf- 

 fered little or no tilting. The creek is cutting into the valley al- 

 luvium, though sometimes meandering at periods of overload or 



