28 
GEOLOGICAL REPORT-THIRTY-FIFTH PARALLEL. 
The gorge called Canon Blanco commences nearly west of Cuesta, and is formed "by the erosion 
of the strata of the Llano. Mr. Marcou considered the strata in the bottom of the gorge to be 
of the age of the upper trias ; while the bluffs are of white and yellow sandstone, with some 
interposed beds of grey marl and a greyish-white nodular limestone. No fossils were seen. 
He also records that these strata are inclined towards the E.E.S., the heads of the strata being 
turned towards the mountains. (See notes, September 30.) This is the first observation of a 
disturbance of the strata of the Llano, but the extent of it, the angle of dip, is not mentioned. 
The peculiar form of the canon and the topography show, however, that this dip must be very 
slight. 
Lieutenant Simpson describes this canon as a “sufficiently wide and smooth defile, the 
escarpments of which run up on either side in places to at least 1,000 feet.” The end of this 
canon is at Lagunas, Camp No. 56 of the survey, and No. 55 of Mr. Marcou’s notes. This 
camp is on the summit or swell of the ground which divides the waters of the Pecos from those 
of the Galisteo, a tributary of the Rio Grande del Norte. At this point the line of survey turns 
southwestwardly to the entrance of the San Antonio Pass, at the southern end of the Gold 
mountains, and at the base of the Sandia range. Mr. Marcou’s trail diverged from this towards 
the northwest, along the road to Santa Fe, through the valley of the Galisteo. In this valley, 
before reaching the village of Galisteo, Mr. Marcou notes the occurrence of upraised white and 
yellow sandstone, trending north and south, and the strata dipping east and west at angles of 
from 15° to 60°. Farther onward, at the village of Galisteo, he found a trap dyke, cutting the 
white sandstone in a direction “30° E.E.N. to 30° W.W.S.” The colored strata (the “ Tri- 
assic”) were also uplieaved, dipping south-southeast, under angles of 10° to 15°. Volcanic 
cones and lava streams were afterwards found. These volcanic rocks, the dyke and the volca¬ 
noes, are on a basis of granite, forming the lofty mountains east of Santa Fe. 
We have thus traced the stratified formations of the plains and prairies to their western 
boundaries at the foot of the mountains. Their relations to these lines of upheaval and the 
geology of the mountains will be subsequently considered. 
Alluvial Deposites and Drift or 11 Diluvium .”—In describing the strata of the section of the 
route which has been under consideration the superficial deposites or accumulations of pebbles 
and sand have not been regarded. These accumulations are often mentioned by Mr. Marcou in 
his notes, and by Dr. Shumard in his observations on the geology of the adjoining tract, on the 
divide between the Canadian and Red rivers. The deposites will be described under the head 
of Alluvial and Post Tertiary deposites, in the after part of the report. 
