RECONNAISSANCE IN COLORADO AND UTAH 643 
the following quotations among many that might be made will 
suffice. Speaking of the “Triassic” at the head of the Little Dolores, 
the north end of the Uncompahgre Plateau, he says: ‘‘The upper 
beds of the formation, as usual, are lighter colored than those below. 
Near the heads of the creeks they are orange-yellow, becoming pink 
as we go north. Immediately beneath them we have blood-red sand- 
stones which rest on gneissic rocks (29, p. 48). In the Unaweep 
Canyon he says that: ‘‘The white or orange-colored, cross-bedded, 
massive sandstone forms the top of the series” (29, p. 81). And 
again the expression, “the cross-bedded, white sandstone of the 
Upper Trias,” is used (29, p. 82). 
In characterizing the sandstones on the west side of the Plateau 
north of San Miguel River he remarks: ‘‘The upper portion of 
the Triassic beds in this region are light colored; in fact in many 
places they are almost white, and it is only by noticing their structure, 
which remains the same whatever the color, and watching the change 
in color, with their position in relation to the remaining strata, that 
we can identify them. Another point to be noted here is that they 
are directly superimposed on the Archean rocks” (29, p. 55). This last 
sentence refers to the unconformity between the La Plata and the red 
Triassic sandstone, which will be discussed farther on in this paper. 
From the Dolores Valley the La Plata sandstones are continuously 
exposed, through Paradox and Sindbad valleys, around the northern 
and western slopes of the La Sal Mountains to the broad plateaus 
bordering Grand River Canyon below Moab. Peale examined this 
area from the summits of the La Sal Mountains (29, p. 60), and 
Holmes viewed them from the similar commanding peaks of the 
Abajo group. The simple stratigraphy of the area, as far as the 
section from the Dakota to the Trias is concerned, was an open book 
to these experienced field observers, and they agreed in extending 
the units of the areas they had examined in detail through the low 
country which was hurriedly traversed by Peale. 
As the La Plata formation can be traced to the walls of Grand 
River Canyon below Moab, there is little room to doubt its further 
extension to the junction with Green River, some 30 miles, and thence 
down the Colorado to the mouth of the San Juan Valley, 70 miles 
further, to the point where it was traced by Gane, as mentioned. 
