Rocky Mountain Trip 
twelve miles away by 11 o'clock - a fine, large river but a good 
ford. We cross it in a broad valley with slight terraces on the 
sides. In the bluffs about are the outcroppings of the tertiary 
sandstones. Leaving the Rio we cross a Sage flat end march up 
a wash and turning over a low ridge to the north pass through 
the Great Hogback into the valley of the cretaceous shales and 
by way of a fine canon cut by a large creek. The sandstones of 
the Hogback are cretaceous, some 3000 feet thick and correspond 
in horizon to the liesa Verde series. The tertiaries outside are 
the same or closely resemble the tertiaries of the San Juan about 
the mouths of LaPlata and Animas. The latter beds are here nearly 
horizontal, while the sandstones of the Hogback, being firm and 
heavy, are turned up at a high angle 70 to SO 0 and trend in a 
grand curve from the west slope of the Elk Mountains, around to 
the White River agency. The sandstones of this group seem much 
metamorphosed and the coal seams too have been burned out, leav¬ 
ing red bands containing cinder, etc. A valley eroded from the 
cretaceous shales extends along the east base and forms n natural 
pass from the Grand and White river. A dome plateau outlined by 
Ho.l and filled in with red beds, etc., lies still to the east 
of this low valley. An immense deal of the drainage of this 
plateau gathers in this narrow valley and passes out through 
the canon gateway mentioned above. 
Sept. 50th; white River Agency. 
'lA- K -v 'V -4 
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