30 
GEOLOGY 
By the side of these Cretaceous rocks , at the foot even of the Llano , are beds of red sand- 
stone , with variegated marls , forming the summit of the Trias ; which are surmounted by whitish- 
gray limestone with flint. Some beds are oolitic, very white, chalky; and the first strata are 
formed of a very hard conglomerate, often very fine-grained, and then passing to a pinkish sand- 
stone. These rocks, covering the Variegated Marls of the Trias, form the whole plain of the Llano 
Estacado as far as the river Pecos; they belong to the Jurassic epoch. Fragments of the Gryphwa 
dilatata var. Tucumcarii are found in the limestone — a species of fossil very characteristic of this 
formation at Plaza Larga and at Tucumcari Mount, near the Canadian river. These rocks of the 
Llano Estacado dip gently east-south-east; and as the heads of the strata outcrop at the foot of 
the Rocky Mountains — called Sierra de Manzana, Sierra Bianca, Sierra del Sacramento — in having ar- 
tesian wells on any point of the Llano, abundant columns of water would be found to gush out 
over this immense plain; so that the want of water is not an objection to the establishment of a 
railroad on the Llano Estacado, for it may be obtained everywhere. 
Descending the cliffs of the Llano Estacado which border the river Pecos, at the foot of the 
bluffs are found again the Variegated Marls, the red sandstone, and finally the crystallized and sac- 
charoid or amorphous gypsum. 
At the junction of the Delaware creek with the Pecos , there are found in the bed of the Rio 
Pecos thick strata of dolomitic limestone; further down it is red, friable sandstone, very easily de- 
composed. On both sides of the Pecos there is drift and a sort of Quarternary conglomerate, formed 
of the rolled fragments of all the rocks through which the Pecos runs , from its source to the east 
of Santa Fe. This drift is chiefly composed of sand, and qiiartzose rocks in small, rolled frag- 
ments. 
Ascending Delaware creek to the base of Guadalupe mountains, there is an immense field, for 
fifty-eight miles, of white gypsum, amorphous or crystallized, with some beds of red and gray 
sandstone of the Trias. These gypsum rocks are prolonged along the river Pecos to Horse Head 
crossing, and they surround the southern foot of the Sierra of Guadalupe, forming the saliferous 
basins of the Salt lake, fifteen miles to the south of the road to El Paso. 
At the headwaters of Delaware creek. Independence spring and the Ojo of San Martine come 
out from grayish Jurassic limestone, the same as that forming the Llano Estacado. As the beds 
here are raised by the dislocation of the Sierras of Guadalupe , of Cornulas , of Los Alamos , of 
Sacramento, etc., in ascending to the Guadalupe Pass, all the strata of the Trias and Jurassic are 
passed through; the Jurassic limestone being covered hereby grayish-white sandstone, often yel- 
low, as at Tucumcari Mount and Caiion Blanco, near Anton Chico. In descending the west side 
of the Sierra of Guadalupe, and traversing the various other chains which intervene before reach- 
ing El Paso, the Carboniferous limestones are found strongly upheaved and in contact with the 
eruptive rocks , which are granite , red sienite , and black sienite , with hornhlend , with the trap 
forming a part of the Organ mountains , and finally with white horizontal sandstone , extending into 
the valley between the sierras. This sandstone is very friable, and decomposes into white sand. 
As far as I can judge without having the fossils of this Sandstone, I think it represents the Vpper 
Chalk, and is only a continuation of the sandstone which extends into the valley of the Rio Grande 
del Norte between Pena Blanca, Albuquerque and Las Limes. 
