* 
LITHOLOGICAL CHARACTERS OF THE GYPSUM FORMATION. 71 
beds of sandy marl, instead of being red and green, are greenish-yellow, and somewhat dolo- 
mitic. Beyond this point, red sandy marls with some green and yellow bands, were constantly 
found. (Notes, September 15 and 16.) The sandstone of Rocky Delaware creek, according to 
the notes, is whitish-grey, with some shales of a rosy hue. The specimen in the collection No. 
65 is a grey, friable, calcareous sandstone, which crumbles away under the fingers. It re- 
sembles recent or Tertiary sandstones. A thickness of 150 feet of red and greyish marls above 
this sandstone is also noted. They have green tints. Beds of shaly sandstones, of a rose and 
red color, are also found. It is possible that these strata belong to the overlying cretaceous de- 
posites of the Llano. Mr. Marcou is of the opinion that the greyish-white sandstone is Triassic, 
and by no means Cretaceous. (Notes, September 18.) In a section of 500 feet in depth, from 
the level of the surface of the Llano downward, the following succession of deposites were found, 
the upper ones belonging to the Cretaceous and not to the Gypsum formation : 
SECTION AT PYRAMID MOUNTAIN. 
( White limestone. ) 
Yellow limestone with bluish-grey bed at the bottom. 
Bed containing Ostrea [——?] 
White sandstone. | "dee" 
Yellow sandstone. 
White sandstone. 
500 feet. 4 Grey and green bed in contact with the superior Trias. 
Red and green sandstone. 
White marls with [concretions ?] 
Red and green marls. 
White. 
[o J 
Mr. Marcou places the dividing line between the Trias and the formations above at the base 
of the lower bed of white sandstone, in contact with a thin bed of grey and green earth or sand- 
stone. He also states that the red clay predominates, and has green and white bands, while 
the red is sometimes wine-colored, and much resembles the Keuper of Brissot. The only indi- 
cation of the line of separation between these formations appears in this case to be the color, for 
no fossils were found. At Anton Chico red marls occur, and appear to predominate from this 
place west to the mountains, forming the bottoms of the caiions. 
West of the Sierra Madre the reddish sandstone and clay was found in the beds of the brooks. 
Near Camp 75 crystals of gypsum were found in the clays and red sandstone; and a short dis- 
tance beyond, a sandy red clay, sometimes brownish-red at the base, was abundant, and many 
fossil trees were seen. Between Camps 76 and 77 the great number of fossil trees already de- 
Scribed was found. Here the sandstone was grey in color, or pinkish, very hard, and thickly 
bedded—the layers being from three to six feet thick. The red clays are, however, said to pre- 
dominate, and a little whitish-grey clay was seen. This was regarded as the middle part of the 
Trias by Mr. Marcou. (Notes, December 3.) Red, blue, and grey clays, supposed to belong 
to the inferior Trias, were subsequently found, and along the Colorado Chiquito red sandstone 
and marl, with white marls below them, were the prevailing rocks. 
There are several specimens in the collection, labelled Triassic by Mr. Marcou, and they are 
described in Chapter X. The localities from which they were obtained have been described in 
the preceding descriptions. They are all from the Atlantic slope, none being found from the 
red strata in the valley of the Rio Grande or west of the Sierra Madre. They are all soft and 
friable— the clays and marls having, to all appearance, been so soft when collected, that they 
were moulded like wet clay. In hardness they do not compare with the specimens from the 
Gypsum formation brought in by Captain Pope, United States Topographical Engineers, from the 
Toute near the thirty-second parallel. It is, however, very probable that the strata are not 
2 For a description of these specimens, see the writer’s report on the Geology of the route near the 32d parallel: Pacific 
+ ''Triassic."' 
