34 
GEOLOGICAL REPORT—THIRTY FIFTH PARALLEL. 
After passing beyond tlie Puerco, the stream about fifteen miles west of the Eio Grande, be 
notes white sandstones and grey clays, and, finally, the red clays of the Trias underlying them. 
As the Puerco has worn a very regular valley in this table-land, and is bounded by it on both 
sides, we may conclude that the characteristics of the strata are tlie same both east and west of 
it. It would appear from tlie note, November 11, that the surface of the mesa between Albu¬ 
querque and Camp 2 is covered with sand, derived from a sandstone beneath, and at tlie Puerco 
a porous, white, and friable limestone is found. Lieutenant J. W. Abert observes in liis report 
on New Mexico, that the mesa or table-land [nearly opposite San Domingo, if I am able rightly 
to locate the description] is 300 feet in height. This cannot be far from San Felipe, and it is 
probably this bluff, crowned with basalt, to which he refers. 1 As he descended the river he 
found that “ the lower strata of the rocks resembled the saliferous formations on the Eio Cana¬ 
dian.” In crossing over the mesa to the Eio Puerco from the place called Atrisco, opposite 
Albuquerque, Lieutenant Abert found the surface sandy and barren. At Poblazon, on the 
banks of the Puerco, where there are ruins, he found a high bluff in one place, presenting an 
abrupt face of 180 feet, and composed of sandstone. These strata contained fossils, “sharks’ 
teeth, shells, and bones of fish.” Professor Bailey, to whom these fossils were referred, made 
the following observations on them : “ The fossils from Poblazon consist of gigantic hippurites ; 
casts from the cells of several species of ammonites; valves of inoceramus identical with a species 
figured in Fremont’s Eeport, Plate IY, figure 2 ; casts of small univalves and bivalves too 
imperfect for determination, and teeth of sharks. These fossils prove that the strata from 
which they were taken belong to the Cretaceous formation.” 2 Figures of some of these forms 
are given in the report. In extending his march westward, Lieutenant Abert followed the 
valley of a stream, and the sandstone formations on each side rose to the height of 600 feet. 
Fragments of carbonate of lime, of ammonites, and of pieces of Inoceramus , strewed the ground, 
and “the little knolls glittered with plates of selenite.” This mineral appeared very abundant, 
and could be seen glittering on the sides of distant mountains. 3 At Moquino, a place due 
west from Albuquerque and the Sandia mountain, and at the western base of the volcano San 
Mateo, the surrounding country consists of masses of sandstone, overspread by basaltic lavas. 
By these fossils, so fortunately collected by Lieutenant Abert, we are authorized to conclude 
that the white sandstone of the mesas of that region is of Cretaceous age. Of the thickness 
of the formation at this point it is of course impossible to decide with our present limited 
information, but it is probable that all the strata exposed along the Eio Grande and Puerco 
are Cretaceous. 
Alluvial deposites. —The eastern bank of the Eio Grande does not appear to be bordered by 
bluffs, except at a few distant points. For several miles above the mouth of the Santa Fe river 
both sides of tlie stream are bordered by bluffs, and the valley is narrow, affording no space for 
agriculture or settlements. South of the Santa Fe the valley widens, and in places the alluvial 
formation attains a width of several miles; but it is generally narrow, and the soil poor. It is 
described as a sandy plain, and only cultivable where well irrigated by canals from the river. 
According to Major Emory, the valley below Angosturas “ opens into a plain, varying from two 
to six miles in width, generally sufficiently low and level to admit the water of the river to be 
carried over it for the purposes of irrigation ; but the soil is very sandy, and better adapted to 
Indian corn than to wheat.” 4 
Opposite Sandia the river is said to be about 100 yards wide, “and, as usual, sandy, shallow, 
everywhere fordable, and nowhere navigable, not even for canoes. Vegetation, except on the 
water-course, is poor, the soil generally sandy and dry.” 5 At Albuquerque, where the river 
1 See Abert’s Report, 1846-’47, p. 463. 
2 Professor J. W. Bailey, in Abert’s Report, New Mxeico, 1846-’47. 
3 Abert’s Report. 
4 Emory’s Report, p. 39. 
* Wislizeuus’s Report, p. 34. 
