peale.] RESUME — CENOZOIC KOCKS TERTIARY QUATERNARY. 641 



The Bridget Group is seen only in isolated places, where the underlying 

 Green Eiver Group is horizontal, so that it is impossible to say posi- 

 tively whether it was involved or not. There is no evidence in our dis- 

 trict of disturbance at the end of the Wahsatch, at the end of the Green 

 Eiver, nor at the end of the Bridger. The elevation was, however, 

 probably before the Pliocene, as the valley of Bear Eiver below Bear 

 Lake appears to have been eroded after the elevation of the Wahsatch 

 covered Bear Lake Plateau. On the latter the Wahsatch beds show a 

 gentle synclinal, and west of it dip steeply from the east side of the 

 Bear Eiver Bauge. At no point in the Green Eiver Basin did I dis- 

 cover any Pliocene beds, so that the continuous uninterrupted section 

 from the beginning to the end of the Tertiary cannot be made from the 

 data obtained by us. 



At the end of the Pliocene-Tertiary there was a great disturbance, 

 which outlined the areas to be occupied by the Quaternary lakes. It is 

 hard to say whether the lakes continued from Pliocene into Quaternary 

 time, with simply a restriction to smaller areas and changing of their 

 outline, or not. If the beds in Bear Eiver Valley below Georgetown 

 are Pliocene, and those beneath the basalt near Soda Springs are Qua- 

 ternary, it would seem to indicate a period of erosion separating them. 



La Cache Valley it is somewhat difficult to separate the Pliocene from 

 the Quaternary, but wherever the former are seen they are always dis- 

 turbed, giving evidence of the Post-Pliocene disturbance. 



QUATEBKAEY. 



In the general section given on p. 612, the Quatenary Groups of the 

 district are given, not in the order of age, but according to their geo- 

 graphical position, with the exception of the drift, which is, of course, 

 the latest. It is found impossible to treat the Quaternary formations of 

 our district in a more systematic way than to take them up in the order 

 there given. 



Drift. — In nearly all the valleys and over large areas of comparative 

 uniformity in level in the district there is spread a thin covering of drift, 

 which is generally very local, being derived from the adjacent mountains. 

 In Salt Eiver Valley, however, the drift is conspicuous in the lower por- 

 tion and is probably of glacial origin. The Salt Eiver Eange and the 

 Wyoming Eanges appear to have had glaciers in their deep canons, and 

 at present have immense snow-banks, that during ordinary seasons do 

 not entirely melt. 



Salt Lake Conglomerate. — At various points in the lower valley of Salt 

 Eiver, especially on the eastern side, there are fragments of a limestone 

 conglomerate, which is horizontal in position. I have included it with 

 the Quaternary, although no facts were observed bearing on its age. 



Malade Valley Group. — The soft sands and marls of Malade Valley 

 containing forms of fresh-water shells are probably somewhat more mod- 

 ern in date than the similar beds in Cache Valley. 



Cache Valley Croup. — This name I have applied to the soft marls and 

 sands which are best exposed in the northern side of the valley and on 

 Bear Eiver below the middle canon. They are somewhat variegated and 

 horizontal in position. The beds in the central portion of Gentile Valley 

 containing Limncea Planorois and other fresh- water fossils are probably 

 of the same age as are also possibly those of Malade Valley just men- 

 tioned. 



The soft sandstones seen in the terraces back of Logan are, I think, 

 older, and probajbly should be classed with the sandstones of Marsh 

 41 g s 



