DISTURBANCES OF THE CARBONIFEROUS STRATA. 67 
river east to the Hot Springs and thence to Little Rock, is an older dislocation. The horizontal 
position of the carboniferous strata on the edges of vertical and contorted metamorphic schist at 
Little Rock, favors this belief; and yet the long lines of ridges of carboniferous sandstone, ex- 
tending on the south bank of the river, parallel with this line of igneous and metamorphic strata, 
show extensive disturbances, and render it more probable that the elevation of Delaware mount- 
ain pertains to the same system. At Mammelle mountain, according to Mr. Featherstonhaugh, 
the strata are well exposed and stand at an angle of 75°, and in some places they were vertical. 
Dardanelle rock, of which a sketch is here given, is formed of highly inclined strata, the in- 
clination being at least 45°. 
Mr. Marcou, however, does not record any inclination so great as these. Between Camps 8 
and 9, the dip was found to be from 20 to 30 degrees, and on Gaines’ creek it was only 15 de- ` 
grees, and at several other points it ranged from 10 to 15 degrees. A cause for these slight 
uplifts may be found in the trap-dykes which Mr. Marcou states are found to traverse the forma- 
tion in that region. 
Near the outcrop of granite at the Caddo village, or not far from Fort Arbuckle, Dr. G. C. 
Shumard found the limestone to be elevated at an angle of 30 degrees, and at another locality, 
further west, he found outcrops of sandstone dipping at an angle of 40 degrees.! The outcrop of 
limestone is nearly south of Delaware mountain, and it is probably a part of the same uplift. 
The extent of the inclination of the strata at the summit of the Sierra Madre is not expressed 
in degrees; it is merely noted that the inclination is very strong towards the west. West of 
San Francisco mountain, at Camp 96, the sandstone strata were found to stand at angles of 60 
or 80 degrees, the general direction of the heads of the beds being W.W.N. (Notes, January 
10.) Itis probable that this is a local rupture of the strata, for they appear to have been found 
horizontal before reaching the next camp. The strata forming the bluff at the Aztec mount- 
ains are not perfectly horizontal, but have a slight dip towards the north. (Notes, January 19.) 
"The strata being completely hid from our view by more modern deposites of great thickness, 
between the several points of outcrop just enumerated, it is not possible for us to affirm posi- 
tively regarding the position or amount of disturbance of these portions; but we are warranted 
in believing that the beds are much undulated, and perhaps in many places come nearly to view 
above the more recent deposites. The carboniferous limestone, and the sandstones above it, 
dip under the beds of the gypsum formation at Delaware mountain, to appear again six hun- 
dred and fifty miles further west on the side of the Albuquerque mountains. The depth to 
which the limestone extends below the surface at any intermediate point cannot be given; but 
the strata probably do not form one great curve, but rest in a succession of wave-like flexures, 
at about the same distance from the surface. Inrepresenting these portions of the strata on the 
Section, the lines are drawn more evenly and regular than it is probable a close conformity to 
nature would permit. The uncertainty which attends their position is, however, acknowledged 
by the broken or dotted line between those portions of the strata which are below the line of 
vision. No outcrop of the limestone and sandstone being found on the western side of the Al- 
buquerque mountains, we are led to conclude that the edges of the strata are covered from view 
by the more recent deposites. Itis also doubtful whether they rise to the surface on the eastern 
slope of the Sierra Madre, Mr. Marcou not being positive that they were passed by him. Mr. 
Campbell, however, having found outcrops of limestone further north dipping to the east, 1t 
becomes most probable that Mr. Marcou's supposition was correct. I, however, have not brought 
the strata to the surface on the section, but have represented them as underlying the whole 
valley, their edges being concealed on each side by the deposites of the gypsum formation or the 
retaceous. a 
Denudation.—It is very evident that the carboniferous strata have been subjected to powerful 
- denudation, it being sufficiently attested by such remnants of the strata as Sugar-loaf mountain, 
1 Marcy’s Report, pp. 193 and 195. 
