MARVLXE.] GEOLOGY GLACIAL OF MIDDLE PAEK. 157 



zons of coarse sandstones, which are often inclined to grits and fine 

 conglomerates. The texture of the latter is usually open and not firmly 

 compacted, while the material of which they are composed is character- 

 istically the debris of the arch?ean rocks of the mountains, granitic de- 

 bris prevailing. While some of the finer-grained massive beds are som- 

 ber brown in color, the usual colors are light gray or whitish. Escarp- 

 ments of the harder gravels, reaching 30 feet in height, separated by 

 shaly slopes of 5 to 10 feet, often make up the hill-sides, while every few 

 hundred feet in altitude a predominance of the more massive gravels 

 has caused the erosion to carve the whole formation into a series of high 

 terrace-like steps, in places well defined, but in others indicated only by 

 changes of steepness in the long, wavy, graceful slopes of the hills. It 

 generally forms a high broken-terraced region. Imx^ressions of decid- 

 uous leaves are quite numerous at favorable localities and small isolated 

 patches, and one or two thin seams of carbonaceous material were also 

 observed, No other fossils were observed in these beds. It has been 

 strongly afifected by the last great folding accompanying the formation 

 of the Eocky Mountains, portions of it being abruptly upturned, to- 

 gether with the underlying sedimentary rocks. In position and char- 

 acter, therefore, this group of beds appears to be the equivalent of the 

 lignitic group east of the mountains. Here, as there, in view of the 

 as yet disputed age of these beds, whether Cretaceous or Eocene-Ter- 

 tiary, and to avoid possible error, the non-commital name of lignitic 

 formation will be at present retained. These beds are intersected to 

 their highest points by dikes of handsome light-gray, porphyritic 

 trachite. 



LAKE BEDS OF THE MIDDLE PAKK. 



After the lignitic there is a geological break, the beds next following 

 being of far more recent age. These occur nowhere at the higher eleva- 

 tions, but occupy all the lower basins. In these, and following the 

 streams, they usually form broad, low terraces, often much cut by the lat- 

 eral streams into isolated pieces or long even-topped tongues running out 

 from the valley sides. IvTear the borders of these areas these beds often 

 plainly show that their material was derived from the adjacent rock, 

 often being of coarse, granitic or schistose debris, or of the lignitic sand- 

 stones worked over ; more frequently they are of finer sands and of 

 characteristic marls of exceedingly white color. They are usually found 

 resting on the archaean rocks, as along the Lower Grand, or on the softer 

 shales of the Cretaceous, which, in former times, as now, afforded the 

 weakest lines for erosion to work most successfully at, and which, there- 

 fore, occupy nearly all of the lower areas. Along such lines, then, the 

 streams cutting through these terraced beds, constantly expose beneath 

 them the more or less upturned edges of the Middle Cretaceous beds. 

 They show a thickness of probably not over 300 feet at any one point, 

 though their vertical range seems to reach to or above a thousand feet. 

 A few dips of ten, i)ossibly of fifteen, degrees, were observed in them in 

 the eastern portion of the park. Unfortunately no fossils were found 

 in these beds, leaving a satisfactory determination of their age impos- 

 sible, though they are undoubtedly very late, or, perhaps. Post-tertiary. 

 They may-, following Dr. Hay den, be very appropriately called lake-beds. 



GLACIAL. 



In the Upper Grand, and at the base of the Blue Eiver Mountains, 

 are extensive glacial moraines. Though no good exposure was observed 



