64 
GEOLOGICAL REPORT—THIRTY FIFTH PARALLEL. 
This little sketch of the point of rocks jutting out into the river near Fort Coffee shows in a 
very distinct manner the contact of a body of sandstone with shales below, and the irregular 
decomposition of the sandstone by weathering. The sketch on page 14, taken near the same 
point, also shows the character of the stratification very clearly. Sugar-loaf mountain probably 
presents one of the best vertical sections of the strata to be found in that vicinity. It is at 
least one of the thickest remnants of strata which have been much worn down and removed 
by denudation. Mr. Marcou considered it to be entirely formed of the coal-measures, and 
states that several beds of coal have been found at its base and in the middle. Beds of sand¬ 
stone occur from five to twelve feet thick, and alternate with schistose marls of a blackisli-grey 
color, presenting traces of coal, and sometimes containing thin beds of limestone. An idea of 
the character of some of the beds of sandstone may be obtained from the annexed sketch, taken 
near the summit, by Mr. Mollhausen: 
OVERHANGING LEDGE OF CARBONIFEROUS SANDSTONE—SUGAR-LOAF MOUNTAIN. 
It shows that the sandstone is compact and homogeneous, and capable of resisting the weather 
very well. 
Between Camps Nos. 4 and 5, about thirty miles west of Fort Smith, the sandstone is asso¬ 
ciated with blackish grey schists, and a portion of the sandstone was very ferruginous, and 
pyrites was disseminated in it. A spring was found there, charged with iron and sulphur. 
Between Camps Nos. 5 and 6, the sandstone was found of a red color in the interior, it being 
stained by the oxide of iron. Schists were also found containing concretions. From this point 
westward to Delaware mountain the sandstone beds were often highly ferruginous, and were 
intercalated with blackish shales. 
I do not find any definite information concerning the lithological characters of the coal-meas¬ 
ures or sandstones of the outcrop on the eastern slope of the Sandia mountains. Mr. Marcou 
gives the thickness of the mountain limestone as 300 feet, and the whole thickness of the car¬ 
boniferous as 2,000. There is thus a thickness of 1,700 feet of either shales or sandstones, or 
probably of both. In his Resume he mentions shales or schists only, and it would appear that 
they prevail to the exclusion of the beds of sandstone. 
At the time the Sierra Madre was crossed, it was very cold, and no observations on the min¬ 
eral characters of the sandstone were made. Mr. Marcou was doubtful whether he saw it on 
the eastern side, and on the west no mention is made of any beds except those intercalated with 
the limestone. 
The sandstones beyond Camp 96 were much broken up, and they have a red color. They are 
