GYPSUM FORMATION, ITS PROBABLE AGE. 75 
although very slight, may be referred to erupted rocks in the granitic region of the Witchita 
mountains, 
We may for the most part regard the strata as horizontal, and undisturbed by the uplift of 
either of the great granitic ranges, which are more recent than the Carboniferous. We may con” 
clude from the notes, and the observations of others, and from the topographical indications, that 
the formation extends continuously in nearly hurisontal beds from one side of the central chain 
of mountains to the other, occupying the wide depressions, or passes, between the ranges. It 
occurs, according to Mr. Marcou, along the valley of the Galisteo river, and a short distance 
north of Camp 56, (Galisteo.) This place is directly in the line of the Santa Fé mountains, 
and between their south end and the north end of the Gold mountains. The white sandstone 
and calcareous strata of the Llano are also found to extend through this break in the mountains, 
and are cut by a trap dyke four hundred yards north of Camp 56. (See notes, October 2.) Mr. 
Marcou also records passing from Camp D (probably at Galisteo) to Camp E, or the Pecos 
village, through **caiions in the Trias, as far as old Pecos, the top of the cations being of 
Jurassic sandstone.”? From this I conclude that the ‘‘Trias’’ and the ‘Jurassic’ were horizon- 
tal at the east base of the Santa Fé mountain, and this conclusion is in accordance with the 
topography, as given by Abert and Peck, in their map of 1846-7. I have been thus particular 
to present the evidences of continuity of these deposites from one side of the mountains to the 
other, as Mr. Marcou represents them in his Resumé, as upraised or dislocated by the ** Rocky 
mountains,”” the dislocation of which, he states, took place at the end of the Jurassic period.! 
Having thus shown that the gypsum formation extends from one side of the mountains to the 
other, undisturbed or dislocated only by local intrusions of trap, we may conclude that the prin- 
cipal uplifts of the central chain took place before its deposition, and that a grand continental 
elevation of over seven thousand feet has taken place since that time. 
REMARKS ON THE PROBABLE AGE OF THE FORMATION, AND A CONSIDERATION OF ITS REPORTED SYN- 
CHRONISM WITH THE TRIAS OF EUROPE 
In a formation of this character, where the upper and lower limits have not been clearly 
traced throughout, and where the peculiar conditions which give it a name may occur in strata 
of an entirely different age, either above or below, and which is also without internal fossil 
evidences, we cannot properly speak of it as distinct, or assign it a place in the geological se- 
ries, as one group with an age isolated by time from those above and below. The peculiar 
mineral conditions which distinguish the strata, and which have served to group them for the 
purposes of description, are the result of causes acting since they were deposited, producing ap- 
pearances entirely different from those which characterized them at the time of their deposition, : 
and acting alike on all the formations, either Carboniferous, Triassic, or Cretaceous, without 
regard to their age or separation by time. We cannot, therefore, discuss the age of the strata 
described under the name G'ypsum formation, as if they constituted one separate geological group. 
We cannot, however, lose sight of the possibility that in these deposites so characterized, and 
differing so much from the known carboniferous and cretaceous strata, we may have the equiva- 
lents of formations which occupy the same relative position in other regions. But the observa- 
tions which have been made do not get justify the establishment of bounding lines, and conse- 
quently, as we have seen, no determinations of the thickness can be made. It is true that for a 
considerable distance in the valleys cutting the Llano Estacado, there is a distinct line formed 
by the junction of the white sandstones and limestones above with the red strata below, but at 
many points the strata are all light-colored, and the only distinguishing difference—that of 
color—is wanting. 
These opinions are, however, very different from those presented by Mr. Marcou in his notes 
and Resumé. He recognises a distinct and well-characterized formation, which he considers as 
the p in age of the Trias of European geologists. He gives its whole thickness as fonr 
1 Resumé. Report of Lieutenant A. W. Whipple, H. Doc. 129, p. 46. 
