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WINTHROP P. HAYNES 



formation, whose erosion has formed some rather prominent valleys, 

 as shown on the map and in Figs. 7,8, and 9. These valleys extend 

 in a general north-south direction and are nearly parallel with one 

 another. This repetition of the formation is due partly to folding 

 and partly to faulting. 



The easternmost valley eroded in the Three Forks formation is 

 very narrow and shallow and extends northward along the eastern 



Fig. 8. — Great valley in Three Forks formation. Ridge north of Three Forks 



slope of the range of hills for five or six miles. The exposures are 

 poor because the strata are vertical or overturned and much crushed 

 by close folding. 



This valley, at its southern end, swings around to the west and 

 opens into a much larger valley, which extends to the north for about 

 two miles. The structure which is the cause of this curious arrange- 

 ment of the valley is that of a southward-pitching anticlinal fold 

 which is overturned to the east. The strata in this very large 

 valley are in the western limb of the anticline (Figs. 8 and 9). 



