PROTEROZOIC GEOSYXCLIXES 169 



posited here a maximum depth of more than 37,000 feet of strata, though 

 the individual sections range in thickness from 10,000 to 27,000 feet. 

 There are almost no volcanic materials. The formations are distinctly 

 bedded elastics, with practically no conglomerates, composed chiefly of 

 fine-grained sandstones and shales with a moderate amount of impure 

 limestone and dolomites that contain considerable iron carbonate and 

 silica.-^ They are all shallow-water deposits, the argillites are often 

 banded, rippling and mud-cracking are common, and sometimes also salt 

 crystals. Purple and red colors are not common, the prevailing shades 

 being greenish, bluish, grayish, or whitish tints. Basal conglomerates 

 occur only to the west, and Schofield^* says that the sandstones become 

 coarser in the same direction; therefore a land lay to the west. This is 

 the borderland Cascadia, which came into existence probably earlier than 

 the Cordilleran geosyncline. Toward the top of the Beltian series in 

 southern British Columbia occur 300 to 5,000 feet of lavas and sills. 



Toward the top of the Beltian series, in association with the limestones 

 and dolomites, algal deposits (Ciyptozoon-like forms) are common and 

 at times make up thick beds. Walcott^° has also described annelid tubes, 

 and to the writer these fossils suggest marine waters rather than fresh 

 or even brackish ones. 



In northeastern Utah the Uinta reddish (ferruginous) quartzites with 

 some greenish shales are, according to Powell,^^ 12,500 feet thick. They 

 rest unconformably upon Archeozoic formations. 



In the Grand Canyon of Arizona occur, according to Walcott,-^ 12,000 

 feet of more or less red strata, beginning at the top with the Chuar. sandy 

 shales (5,120 feet). Below are the Unkar sandstones and sandy shales 

 (6,830), with some calcareous shale and limestone below (435), along 

 with lava floAvs in the upper part, xlll of the Grand Canyon series is 

 near-shore deposits and much of it is even of fresh-water origin. The 

 sediments came from the north and west. 



In the southern Appalachian geosyncline Keith informs the writer that 

 the late Proterozoic formations consist of lava flows, tuffs, and slates, the 

 flows predominating at the northwest, where land is therefore indicated. 



23 F. C. Calkins : A geological reconnaissance in northern Idaho and northwestern 

 Montana. U. S. Geol. Survey, Bull. 384, 1909. 



-* S. J. Schofield : Geology of the Cranbrook map-area. Geol. Survey Canada, Mem. 76. 

 1915. 



25 C. D. Walcott : Pre-Cambrian Algonkian algal flora. Smithson. Misc. Coll., vol. 64, 

 1914, pp. 77-156 ; Pre-Cambrian fossiliferous formations. This Bulletin, vol. 10, 1899, 

 pp. 199-244. 



26 J. W. Powell : Report on the geology of the eastern portion of the Uinta Mountains. 

 U. S. Geol. and Geog. Survey Terr., vol. 7, 1876. 



2' C. D. Walcott : Pre-Carboniferous strata in the Grand Canyon of the Colorado, Ari- 

 zona. Amer. Jour. Sci. (3), vol. 26, 1883, pp. 437-442. 



