6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 57 



There are also thick masses of hmestone interbedded in the Algon- 

 kian series. The Blackfoot terrane has over 4,800 feet of calcareous 

 beds. The Siyeh limestone is 4,000 feet thick, and the Newland lime- 

 stone 2,000 feet. Similar blue, red, and green deposits, if deposited in 

 the ocean, would probably have been accumulated in deep, quiet 

 water [Chamberlin and SaUsbury, Vol. i, 1904, pp. 361-363], but 

 (a) the large amount of calcareous matter ; (b) the presence of 

 shrinkage cracks and ripple markings on shales, sandstones, and 

 limestone shales; (c) the presence in calcareous shales of fossils 

 that lived in shallow water [Walcott, 1899, pp. 235-238], indicate 

 that the Algonkian sediments were deposited in relatively shallow 

 water. 



In speaking of the climatic significance of red-colored deposits, 

 Barrell [Barrell, 1908, pp. 292 and 293] says: 



Turning to the climatic significance of red, it would therefore appear both 

 from theoretical considerations and geological observations that the chief 

 condition for the formation of red shales and sandstones is merely the alter- 

 nation of seasons of warmth and dryness with seasons of flood, by means of 

 which hydration, but especially oxidation of the ferruginous material in the 

 flood-plain deposits is accomplished. This supplements the decomposition of 

 the source and that which takes place in the long transportation and great 

 wear to which the larger rivers subject the detritus rolled along their beds. 

 The annual wetting, drying, and oxidation not only decompose the original 

 iron minerals but completely remove all traces of carbon. If this conclusion 

 be correct, red shales or sandstones, as distinct from red mud and sand, 

 may originate under intermittently rainy, subarid, or arid climates without any 

 close relation to temperature and typically as fluvial and pluvial deposits upon 

 the land, though to a limited extent as fluviatile sediments coming to rest 

 upon the bottom of the shallow sea. The origin of such sediment is most 

 favored by climates which are hot and alternately wet and dry as opposed to 

 climates which are either constantly cool or constantly wet or constantly dry. 



Origin of Later Algonkian Rocks. — The question under this head- 

 ing is as to whether the rocks of the Belt series of Montana, the Grand 

 Canyon series of Arizona, the Llano series of Texas, the Avalon series 

 of Newfoundland, and more doubtfully the Keweenawan series of 

 the Lake Superior region, are of marine or of terrestrial origin. 



By referring to the accompanying map of the later Algonkian 

 rocks we find that all of the known areas are within the limits of 

 the outline of the continental platform, even those of Newfoundland 

 and Nova Scotia being 150 miles within that platform. With this in 

 view I will first call attention to the origin of the great series of 

 Tertiary terrestrial non-marine sediments in the western section of 

 the continent, for the solution of that problem has a most important 

 bearing on the probable origin of the Algonkian sediments. 



