128 JOSEPH E. POGUE 



earth movement followed deposition is clearly evidenced by the 

 present folded character of the sediments. 



The freshness and variety of the components of the conglom- 

 erate and finer sediments point to derivation from a region of rugged 

 and youthful topography under conditions of intense mechanical 

 disintegration characteristic of a climate in which frost action 

 played an important part. The presence of carbon and plant 

 remains in the finer members of the formation indicates deposition 

 under conditions unfavorable to oxidation, while the character of 

 the plants themselves implies a temperate climate in the area of 

 deposition, markedly milder than that of the region today, and in 

 contrast also to the more rigorous conditions that prevailed in the 

 high mountains from which the sediments were derived. The thick- 

 ness and extent of the conglomerate members, moreover, seem to 

 indicate a more vigorous precipitation than at present, capable of 

 handHng the abundant waste of the mountains. That this upland 

 was the seat of active glaciation and consequently contributed 

 glacial materials to the streams sweeping the Cantwell sediments 

 downward is regarded as probable, though no observations can be 

 adduced in support of this belief. 



The presence of red sandstones toward the top, as noted by 

 Brooks in the western portion of the formation, is not believed to 

 have climatic significance f for organic colors are conspicuous 

 throughout that portion of the formation also. These members 

 are rather suspected of expressing a variant in the lithology, or a 

 change in the topography, of the source of supply. 



The situation of the Tertiary land mass in reference to its basin 

 of deposition cannot be given without reservation, but the present 

 dehneation of the Cantwell formation and the fact that its coarser 

 members contain fragments of slate similar to that of older forma- 

 tions to the south and dissimilar to sediments exposed to the north 

 suggest a position south of the present area of Tertiary rocks. 



' See Willis, Jour. GeoL, I (1893), 478. 



^ Barrell (Jour. GeoL, XVI [1908], 293) observes that ". . . . red shales or sand- 

 stones, as distinct from red mud and sand, may originate under intermittently rainy, 

 subarid, or arid climate without any close relation to temperature and typically as 

 pluvial or fluvial deposits upon the land " 



