CRETACEOUS FORMATION—FOSSILS—LLANO. 
79 
CRETACEOUS. 
The route followed by the expedition having been, for a long distance west of Little Rock, 
in the valley of the Arkansas and Canadian rivers, and along the broad belt of carboniferous 
strata extending southwesterly into Texas, no deposites, which could be recognised as cretaceous, 
were seen until Camp 31, on the False Washita, was reached. It is, however, well known that 
the cretaceous formation is well developed around Fort Washita, a point nearly south of Dela¬ 
ware mountain, and it probably extends nearly parallel with the route, but south of the car¬ 
boniferous hills, nearly to Little Rock, where it disappears beneath more modern strata, and is 
again exposed on the east side of the Mississippi, in the States of Mississippi and Tennessee. 
The now well-known cretaceous fossil, Gryphcea Pitcherii, was originally obtained from the 
Kimichi Plains, south of the route between Little Rock and Fort Smith. The same species, 
according to Mr. Marcou, was obtained on the route at Camp 31, on the False Washita, together 
with fragments of Ostrea and Pecten quinque costatus. Specimens of the gryphrea are in the 
collection, (see catalogue and description, and Plate I, fig. —;) but there are no specimens of 
the other fossils. The next point which is identified as cretaceous by the fossils is in the valley 
of the Canadian, at Pyramid mountain, one of the remnants of the plateau of the Llano. Here 
Mr. Marcou obtained a gryplima, which he at first considered a new species, and called it 
G. Tucumcarii. He, however, does not regard it as a cretaceous fossil, but as Jurassic. 
North of this place, in the valley of the Arkansas, numerous specimens of Inoceramus were 
obtained from similar positions in the bluff borders of the plateau, by Dr. Scheil, who accom¬ 
panied Captain Gunnison, and they were also found there several years ago, by Dr. A. Randall. 
Lieutenant Simpson also mentions the occurrence of similar fossils in the vicinity of the Tucum- 
cari hills, or Plaza Larga. 1 Dr. Wislizenus found casts of Inoceramus in the schistose lime¬ 
stone of the bluffs of Gallinas creek, and describes the strata as Cretaceous. 2 Mr. Marcou also 
saw imperfect fossils from the bluffs near Camp 46, which led him to conclude the Llano to be 
Cretaceous. (Notes, September 18th.) Passing further west, cretaceous fossils were obtained 
by Mr. Marcou about three miles north of Galisteo, in sandy clay and sandstone. (See notes, 
October 10th.) Mr. Marcou mentions a tooth and vertebra of a Saurian and an Ostrea , also 
Inoceramus or Plicatulus. Specimens of sandstone from this place, containing fragments of 
fossils, are in the collection. (See No. 126 of the catalogue.) This locality is between the 
south point of Santa Fe mountain and Gold mountain, nearly at the summit of the pass in the 
mountains, and on the borders of Rio Galisteo, one of the tributaries of the Rio Grande. The 
same deposite is mentioned in the Resume, and is there referred to the age of the white chalk. 
I also find in the collection a specimen, No. 131, labelled as taken from a point near Las Lunas, 
between the Rio Grande and the Puerco; also, a specimen labelled Terrain Cretace , from a point 
between Galisteo and Gold mountain. Mr. Marcou also mentions, in his notes of November 
28th, the occurrence of rolled or worn specimens of Grypliwa , which appeared to be Jurassic. 
This was beyond Zuhi, west of the Sierra Madre. The collection does not contain any of these 
last-mentioned specimens. 
Most, if not all, of these cretaceous fossils were procured from the edges of the horizontal 
strata which compose the extensive table-lands along the route, and they indicate to us the cre¬ 
taceous age of the Llano Estacado. Further evidence of this is found in the collection made by 
Captain John Pope, on the Llano, further south, near the parallel of 32°. He procured speci¬ 
mens of Gryphcea in the bluffs of the Llano at the Big Springs of the Colorado, and also on the 
surface, near the sand-hills, and these fossils, together with the specimens of the strata and 
other evidences, led me to describe the Llano as Cretaceous, in the report on the geology of that 
See Simpson’s Report, and Chapter II of this Report. 
2 See Wislizenus’ Report, page 17, and Chapter - II of this Report. 
