CONTINENTAL DEPOSITS OF ROCKY MOUNTAIN REGION 601 



as " turbulent." It is quite possible that certain authors intended to include sub- 

 aerial marginal deposits under the general heading of lacustrine deposits, and that 

 they tacitly allowed a considerable volume to deposits thus accumulated, although 

 there is repeated implication that even the coarser sediments were laid down on 

 the lake side, not on the land side of the " shorelines," below water-level and not 

 above. River action may have been taken for granted, as so naturally associated 

 with lake deposits that no mention of it was thought to be necessary. However 

 all this may be in the minds of the writers, there is no question that the readers of 

 the reports of the western surveys will be led by the repeated mention of lakes 

 and by the almost universal silence about rivers to regard the whole body of the 

 western Tertiaries, coarse and fine, as lacustrine, and a reference to the text-books 

 above mentioned will substantiate this statement. Whatever qualifications of the 

 lacustrine theory may have been in the minds of the older geologists, who are 

 familiar with the facts by direct observation, it is not likely that any qualifications 

 of the theory will enter the minds of the rising generation of geologists when they 

 first meet the current descriptions of the wonderful lake deposits of the West in 

 text-books or in governmental reports, and it is particularly in this connection that 

 it seems advisable to promote discussion on the subject here presented. 



More important than the tacit qualifications of the lacustrine theory that may 

 have a place in the minds of some geologists, the expressed opinions of other geol- 

 ogists on this subject deserve mention. In the first place, it should be pointed 

 out that the investigations of the Quaternary lakes of the West seem to have been 

 conducted on somewhat different principles from those which obtained in the 

 study of the Tertiary lakes. In the Bonneville and Lahontan basins intercalated 

 deposits of gravels and sands are taken as indicating a non-lacustrine interval be- 

 tween the lacustrine epochs in which underlying and overlying marls and clays 

 were laid down. Furthermore, the Pliocene sediments of the plains in Colorado . 

 and Kansas have been explicitly described as fluviatile by two observers, Gilbert 

 and Haworth, and the eolian origin of the White River clays of Nebraska has 

 recently been discussed by Matthew. In Europe Penck has called attention to 

 the essentially fluviatile origin of such basin deposits as occupy the plains of Hun- 

 gary and of the middle Khine, and it is from this geologist that I have learned the 

 term continental as a general name for lacustrine, fluviatile, and eolian deposits, 

 in contrast to marine deposits ; and both Penck and Goodchild have attributed 

 the heavy and coarse Torridon sandstones and conglomerates of northwest Scot- 

 land to accumulations on an arid land surface. In view of all these considerations, 

 it does not seem too much to say that the habitual explanation of our western 

 fresh-water Tertiary formations as lake deposits stands in need of thorough and 

 critical revision. 



Discussion 



F. S. Emmons said 



That Professor Davis' remarks seemed to apply specially to the Fortieth Parallel 

 work, in which he took part, since theirs was the first to attempt to differentiate 

 and roughly outline the Tertiary basins of the Rocky Mountain region. He seemed 

 to imply that these geologists had assumed that any non-marine Tertiary beds 

 observed were necessarily deposited in a Tertiary lake without stopping to consider 

 the possibility of any other origin. Their geological work was confessedly not a 



