REPORT OF TEE CHIEF ASTRONOMER 555 



SESSIONAL PAPER No. 25a 



Correlation within the Western Geosynclinal Belt. 



Even a superficial comparison of the older reports on the geology of 

 California, Nevada, Oregon, and southern British Columbia with the newer 

 results won in Alaska, Washington, Idaho, and British Columbia, as well as on 

 the Forty-ninth Parallel, suffices to show that the geological development has 

 been remarkably similar all along a broad coastal zone from northeastern 

 Alaska to southern California. This relative -uniformity in the history of the 

 large and extremely complicated zone has long been recognized in a qualitative 

 way. More or less explicitly the idea has often been expressed in the 

 literature that this western zone stands in vital contrast to the somewhat wider 

 band of rocks extending from northern Alaska to Arizona and generalized in 

 the present report under the name ' Eastern Geosynclinal Belt.' The facts 

 obtained during the six seasons of field work on the Forty-ninth Parallel tend 

 to confirm these broader views of the earlier students of the Cordillera, and 

 it seems useful to note some of the principal correlations within the western 

 zone, here called the ' Western Geosynclinal Belt.' 



The work of constructing the general correlation table (XXXV) has been 

 greatly facilitated by the recent publication of Brooks's ' Geography and Geology 

 of Alaska,'* Dawson's ' Geological Record of the Rocky Mountain Region in 

 Canada,'f the various folios published to date by the United States Geological 

 Survey on areas in Washington, Oregon, and California,^; and among the special 

 papers, a valuable one by Diller and Stanton on the Shasta-Chico Series. § 



The correlation may prove to be erroneous at certain points but the general 

 truth that formations older than the Upper Carboniferous seem to be extremely 

 rare in the Western Geosynclinal Belt, may be definitely stated. The apparent 

 rarity may, of course, be partly due to the heavy metamorphism which 

 characterizes the belt from one end to the other. On the other hand, it has 

 been proved that the Devonian and Silurian sediments where actually found, are 

 comparatively thin, and we have already seen that during the very long Cam- 

 brian-Beltian period of continuous sedimentation in the Eastern Geosyncli- 

 nal Belt the Western Belt must have been largely out of water and suffering 

 erosion. The oldest Paleozoic beds which play so important a role in the 

 Eastern Belt should not be expected in the Western except, perhaps, in the form 

 of local transgression deposits. The same reasoning may in a measure be applied 

 to much of the Devonian period during which clastic materials, derived from 



* Professional Paper No. 45, U.S. Geol. Survey, 1906, by A. H. Brooks. 



t G. M. Day-son, Bull. Geol. Soc. America, Vol 12, 1901, p. 57. 



J Snoqualmie folio (G. 0. Smith and F. C. Calkins, 1906); Ellensburg and Mount 

 Stuart folios (G. O. Smith, 1903 and 1904) ; Tacoma folio (B. Willis, 1899) ; Roseburg, 

 Coos Bay and Port O'rford folios (J. S. Diller, 1898, 1901 and 1903); Jackson folio (H. W. 

 Turner, 1894) ; Smartsville folio (W. Lindgren and H. W. Turner, 1895) ; Lassen Peak 

 folio (J. S. Diller, 1895); Pyramid Peak and Truckee folios (W. Lindgren, 1896 and 

 1897) ; Sonora folio (H. W. Turner and F. L. Ransome, 1897) ; Downieville and Bidwell 

 Bar folios (H. W. Turner, 1897, 1898) ; Big Trees folio (H. W. Turner and F. L. Ran- 

 some, 1898) ; Colfax folio (W. Lindgren, 1900) ; Mother Lode District folio (F. L. Ran- 

 some, 1900); and Redding folio (J. S. Diller, 1906). 



§ J. S. Diller and T. W. Stanton, Bull. Geol. Soc. America, Vol. 5, 1894, p. 436. 



