8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 57 



I find in my field notes of 1879, on the Tertiary section at the head 

 of the Upper Kanab Valley in southern Utah, the following on the 

 fresh-water beds : 



FEET 



a. Light gray limestone with Physa and Planorbis 125 



b. Pink arenaceous marls 180 



c. Light gray limestone 20 



d. Marl 40 



e. Pink limestone 50 



f. Light gray limestone 125 



g. Pink limestone 100 



h. Sandstones with fine conglomerate at the base 625 



The limestones extend over a considerable area west, north, and 

 east, and were deposited in massive layers in a deep, quiet lake. 



The Tertiary sedimentation described above, omitting the eruptive 

 materials, is very similar in many respects to that of later Algonkian 

 time. The sediments of the Algonkian are as a whole more siliceous, 

 but the variation in thickness and character of the various beds 

 [Walcott, 1906, pp. 17-21] is of the same general type. 



The sediments of the two widely separated periods of Algonkian 

 and Tertiary time were accumulated within the liinits of the great 

 Cordilleran geosyncline, and, with our present knowledge, I think, 

 under essentially similar physical conditions. At the time of the 

 Tertiary deposition there was abundant life, both on the land and in 

 the water, but in Algonkian time only a fragment of the pre-Cam- 

 brian life had had the opportunity of adapting itself to the conditions 

 of the inland seas of late Algonkian time. 



Dr. Joseph Barrell has given a full review of the evidence favor- 

 ing the continental origin of most of the Algonkian rocks of the 

 Cordilleran area. He argues that from the presence of mud-cracks 

 in the Belt and Grand Canyon series that many of the formations 

 were deposited on flood plains. He says [1906, p. 566] : 



The discussion of these pre-Cambrian deposits but especially of the Montana 

 occurrences, shows how completely in accord is the hypothesis of the dominant 

 flood-plain origin of mud-cracks with the other marks of subaerial deposition 

 in an arid climate. The mud-cracks are confined to just such formations as 

 from other characteristics suggest a flood-plain origin and these formations 

 are usually separated from the deposits of limestone by transitional forma- 

 tions which differ in color, in character, and in the absence of mud-cracks, 

 suggesting the true submarine deposits originating between the shore and the 

 open sea. 



