24 GEOLOGICAL REPORT—THIRTY-FIFTH PARALLEL. 
the western limit. Mr. Marcou observes, under date of September 8th, that at Camp 38, 
* on the right and left banks of the Canadian we find the commencement of the Llano, a sort of 
plateau with some flat, isolated mountains as an advanced guard, similar to the Alb of Wirtem- 
berg near Hedinger and Balenguen.’’ After travelling further westward, Mr. Marcou formed 
the opinion that the strata of the Antelope hills, the grey sandstones, were not the extension of 
the strata of the Llano, but that they underlaid them and formed a part of the ‘‘ Trias.”” 
Captain Marcy, in his explorations at the sources of the Red river, travelled under the eastern 
border of the Llano, and enjoyed an excellent opportunity for locating it on his map and ex- 
amining its characters. He travelled for several miles in a narrow ravine, bordered on both 
sides by vertical bluffs of the horizontal strata over 600 feet high. This was at the head of 
Red river, about fifty miles south of the Canadian. The water there gushes out in a spring and 
flows for a short distance over the white or greyish strata of the plateau. Dr. G. G. Shumard, 
who accompanied Captain Marcy, describes these bluffs as consisting of horizontal layers of 
drift, sandstone, and yellow clay ; and on June 28th the bluffs, ‘‘ six hundred feet high," were 
composed of horizontal layers of drift and sandstone interstratified with white limestone.! In 
the section which accompanies this description the ‘‘drift’’ is represented with a thickness of 
nearly 100 feet, and is succeeded below by grey and yellow sandstones interstratified with thin 
seams of non-fossiliferous limestone ; and this again by gypsum and red clay. It is impossible 
to determine from the section how great a thickness is occupied by the grey and yellow sand- 
stones, but it is certainly not less than 250 feet. It is, however, mentioned on page 192 that 
the inferior strata, or those between the base of the bluffs and the river, consist of gypsum and 
red clay. This leaves the legitimate inference that the yellow sandstones and limestones attain 
a thickness of 500 feet. 
he composition of the bluffs along Encampment creek, a point about half way between 
Camps 45 and 46, the portion of the route which traversed the summit of the Llano, was thus 
observed and recorded by Mr. Marcou, (see notes, September 17) : 
White limestone. 
Calcareous conglomerate. 
Limestones. 
Sandstone with numerous calcareous concretions. 
Red sandy marls of the New Red. 
At Camp No. 46, which was at the foot of the Llano, the following section was noted : 
10 feet—Limestone resembling Forest marble. 
sa marl 
150 feet— - Violet sandstone. 
ed marl. 
100 feet—Grey sandstone, sometimes violet. 
Mr. Marcou further observes, that the sandstone of Rocky Delaware creek (forming the base 
of the section) is whitish-grey, with some shales of a rosy hue. A specimen of this sandstone 
is in the collection, (No. 65,) and is described in Chapter X. It is this sandstone which is 
regarded as Triassic, and which Mr. Marcou, in his notes, thought was the same as that form- 
ing the Antelope hills. (See September 18.) 
Tucumcari Hill.—On descending from the Llano to the valley of Rocky Delaware creek, the 
red-colored strata were again encountered, and the trail passed upon them, with occasional 
exceptions, as far as Hurrah creek, a tributary of the Pecos. The bluffs of the Llano were con- 
stantly in view on the south. Beyond Camp 48, the mound called Tucumcari is found, rising to 
the height of the Llano, but standing apart from it, and completely isolated. This is called 
Cerro Tucumcari by Captain Marcy,? who remarks that it is round and symmetrical, and when 
seen at a distance, resembles the dome of the capitol at Washington. Simpson also remarks 
1Shumard in Marcy's Report, pp. 191, 192. 
* This name appears to have been given to the mound by Gregg. See his work entitled ‘ Commerce of the Prairies.” 
