BOTANY OF LARIMER COUNTY I2I 
sedimentaries the altitude is about 6,900 ft. The highest sedimentary 
ridges and buttes are 7,200 ft. 
The Rock Ridges.—These are the upturned edges of harder layers 
of a sedimentary series lying above the granites of the Rocky Moun- 
tains. The strata dip to the east at some points as much as 20 or 25 
degrees (Owl Canyon) and at others (Red Mountain) they are almost 
horizontal. For some distance south of the Wyoming line the strata 
form a long series of many ridges extending north and south and 
parallel with the foothills. These ridges show the following formations 
named in order from above downward: 
Niobrara Chugwater 
Benton Lyons 
Dakota Fountain 
Morrison 
The lowest member of the series, the Fountain, is a coarse, red conglom- 
erate, in many cases rather difficult to distinguish from the underlying 
granites. Red sandstone is, however, the prevailing material of the 
ridges and this in weathering produces a fine-grained, compact soil. 
Alternating layers of harder and softer material become eroded at dif- 
ferent rates and this leads to the formation of the series of ridges all 
sloping to the east, while on the west there may be rather abrupt escarp- 
ments. (See Figs. 1, 3, 4.) 
The width of the entire sedimentary formation from Fountain to 
Niobrara varies from three to ten miles. Deep canyons are cut through 
the ridges at various points. Generally these take a zigzag course 
first south between two ridges, then east through a ridge, then south 
again. Isolated portions of the ridges are cut off by stream erosion and 
in places where the strata are nearly horizontal steep-walled buttes and 
hills are formed. Some of these have escaped much of the general 
erosion and now tower far above the general level of the surrounding 
ridges. Red Mountain is a good example of this condition. Very 
little soil is to be found on the rock ridges, but here and there a part 
of the ridge has been so eroded as to deposit washings as a small alluvial 
fan. In such places there is grassland, while most of the ridge is covered 
with scrub. 
