TABLE-HILLS AND PLATEAUX—LLANO ESTACADO. 
21 
stone. The strata were decomposing rapidly, and holes or cavities of all shapes were formed in 
them by the weather. I find a specimen of this sandstone in the collection. It is No. 68 of 
the catalogue, and its label by Mr. Marcou states that it is from the upper Trias. The descrip¬ 
tion of this specimen in full will be found in the appropriate place, (Chapter X,) but I extract a 
few lines from it. The specimen presents a remarkable resemblance to several of the sandstone 
specimens collected by Captain Pope near the 32d parallel. The grains are siliceous, white and 
yellow, and are cemented by a large quantity of amorphous carbonate of lime ; in fact the 
grains seem rather to be imbedded in a paste of carbonate of lime. It most resembles No. 29 
of Captain Pope’s collection, found on the surface of the Llano Estacado, forty miles east of 
the Rio Pecos. 1 
We thus have at this locality sandstone formations very different in aspect from the dark red 
and blue clays which contain the gypsum in such large quantities. A marked change in the 
geology commences at this part of the route, and we shall presently see that these isolated 
buttes are probably outlying portions of a widely-extended plateau—the Llano Estacado—which 
was partly traversed by the survey, and the base of which was followed for a long distance. 
From the Antelope hills to Camp 40 the road was continually upon or near white or grey 
sandstone, and the gypsum does not appear to have been seen. 
Mr. Marcou mentions mounds on the left, between Camps 36 and 37, the day’s journey after 
leaving the Antelope hills, and buttes similar to the Antelope hills were mentioned by Captain 
Marcy in 1849, and are laid down by Lieutenant Simpson on his map as north of the road near 
his Camp No. 43. All that country, according to this last authority, is similar, as far as the 
margin of the celebrated plateau—the Llano Estacado or Staked Plain. 
The following is a sketch of one of the table-hills three miles west of Shady creek, near 
camp. 
TABLE-HILL THREE MILES WEST OF SHADY CREEK. 
It shows the mode of formation of these mounds very distinctly, the base of the mound being 
covered with the ruins of the hard stratum on the top. This layer is probably magnesian lime¬ 
stone, as it was found in similar positions in this vicinity by Mr. Marcou, and an outline figure 
of one of the hills, with the blocks on the slope, is given in his notes. 
Between Camps No. 37 and No. 38, the trail crosses the valley of Dry river, so named by 
Gregg, which is bordered by steep and rugged escarpments of rock. This stream affords an ex¬ 
cellent example of the denuding action of running water, and it is noticed by Lieutenant Simp¬ 
son. He states that the soil and sub-strata are composed of a friable white sandstone. From 
a consideration of the appearances presented along the hanks of this atream, Lieutenant Simp- 
1 See the writer’s Report on the Geology of the Route near 32d parallel of latitude, U. S. Pacific R. R. Exploration 
and Survey, vol. ii. 
