ABSENCE OF NORTHERN DRIFT; STATEMENT MADE IN 1866. 73 



Drift " anywhere in the region covered by the observations in the preceding 

 pages. 



It was after some years of exploration in Cahfornia and along the Pacific 

 Coast, by the State Geologist and other members of the California Geological 

 Survey, that the writer published, in ] 866. the following statement in regard 

 to the absence of the Northern Drift formation from the western coast of 

 North America and from the interior of the continent, throuo'hout the region 

 to the southwest : * — 



" The explorations of the Geological Survey of California have demon- 

 strated, however, that there is no true Northern Drift within the limits of 

 this State. Our detrital materials, which often form deposits of great extent 

 and thickness, are invariably found to have been dependent for their origin 

 and present position on causes similar to those now in action, and to have 

 been deposited on the flanks and at the bases of the nearest mountain 

 ranges by currents of water rushing down their slopes. While we have 

 abundant evidence of the former existence of extensive glaciers in the Sierra 

 Nevada, there is no reason to suppose that this ice was to any extent an 

 effective agent in the transportation of the superficial detritus now I'esting 

 on the flanks of the mountains. The glaciers were confined to the most 

 elevated portions of the ranges, and although the moraines which they have 

 left as evidences of their former extension are often large and conspicuous, 

 they are insignificant in comparison with the detrital masses formed by 

 aqueous erosion. There is nothing anywhere in California which indicates 

 a general glacial epoch, during which ice covered the whole country and 

 moved bodies of detritus over the surface independently of its present con- 

 figuration, as is seen throughout the Northeastern States. 



" The same condition of things prevails in Nevada and through Oregon, as 

 far as explored by the members of the Survey. The detritus seems always 

 to be accumulated at the base of the mountains, — gravel, boulders, and 

 sand lying below and not far distant from the beds of rock of which these 

 materials once formed a part, and from which thej^ appear to have been 

 detaclied by weathering and aqueous erosion. 



" From the observations of Messrs. Ashburner and Dall, it would appear 

 that no evidences of Northern Drift have yet been detected on this coast, 

 even as fir north as British Columbia or Russian America. Neither of these 

 gentlemen has observed any indication of a transportation of drift materials 



* Proceedings of the California Academy of Sciences, Vol. 111. [J. 271. 



