THE SIERRAN VALLEYS OF THE KLAMATH 

 REGION, CALIFORNIA. 



In a series of papers recently published^ the writer has traced 

 the development of the present topography of that portion of 

 the Klamath mountain region which lies south of the Klamath 

 river, terminating the story with a great uplift at about the open- 

 ing of the Quaternary era. This history comprised a sharp fold- 

 ing of the sedimentary formations and the injection into them of 

 batholiths of peridotite, gabbro, and granite, at about the close 

 of the Jurassic period ; a profound denudation and leveling off 

 by sub-aerial processes in early Cretaceous time ; a submergence 

 of the border of the province in late Cretaceous time ; a post- 

 Chico deformation, throwing the entire region into a series of 

 deep elliptical basins ; a probable partial peneplanation, the prod- 

 uct, perhaps, corresponding to the Eocene peneplain of south- 

 eastern California ; an uplift resulting in the erosion of broad 

 basins whose floors were probably irregular ; the production 

 beneath the floors of these basins of broad, deep, canyon-like 

 depressions, apparently the result of stream erosion ; the filling of 

 the depressions by thick accumulations of river-channel deposits 

 and the more complete leveling of the basin floors ; and finally 

 the uplift, tilting, and erosion of these old alluvial deposits. 



Along the western border of the Klamath province and in the 

 adjoining portion of the Northern Coast Ranges, Mr. J. S. Diller 

 has encountered a rich territory (for the physiographer) and has 

 recently published his conclusions in an admirable paper entitled 

 "Topographic Development of the Klamath Mountains,"^ the 

 result of several reconnaissance trips into that region. He iden- 

 tified, on the older rocks of the Klamath region, numerous rem- 

 nants of an uplifted and dissected plain of erosion, the Klamath 



^ American Journal of Science, Fourth Series, Vol. XIV, No. 79, July, 1902 ; Science, 

 Vol. XV, June 13, 1902, p. 951 ; JoUR. Geol., Vol. X, No. 4; May-June, 1902, 

 PP- 377-92. 



''Bull. U. S. Geol. Surv., No. 196, Series F, Geography, 31, 1903. 



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