TRIASSIC FORMATIONS. oil 
tion, a process which is characterized by the formation of small translucent 
plates of red hematite somewhat uniformly througbout the mineral. There 
is a cement, more or less abundant, of fine, calcareous material, apparently 
detrital in nature. 
The limestones and lime shales differ again from these sandstones only 
in containing a still smaller proportion of granitic materials and a corre- 
spondingly increased amount of calcareous material. In nearly every 
section almost all the commoner minerals which are ordinarily found in 
eranite are present, tourmaline, zircon, and magnetite being especially 
persistent. These materials are embedded in a very fine-grained calcareous 
cement, which has the appearance of having been deposited as a lime mud. 
The green color of the limestones and shales is due to the presence of 
glauconite, which is often abundant, in green and brownish-green grains. 
TRIASSIC FORMATIONS. 
RED SANDSTONES. 
Lenado Canyon affords a continuous section of the rocks from Lenado 
westward to where the sequence is interrupted by the Castle Creek fault. 
The junction of Weber and Maroon occurs at Lenado; the brown sand- 
stones begin at the mouth of the Bimetallic tunnel and continue for a long 
distance down the stream, which here flows nearly at right angles to the 
strike, thereby affording a complete cross section. At a point about half- 
way from Lenado to the Castle Creek fault there is a marked though not 
abrupt change in the appearance of the beds. The sandstones become more 
massive, though they are still often thin bedded; and the prevailing color 
changes from dull reddish brown to ight red. There are still occasionally 
thin limestone bands; but the red sandstones predominate, and the aspect 
of the outcrops is distinctly changed. There is a similar change in the beds 
in the more southern part of the district examined, although here it is not 
so distinct, and the upper red series appears to be thmner bedded. This 
upper series of more massive and lighter-red sandstones has been provi- 
sionally assigned to the Triassic period. It extends from the rather indefinite 
plane described above up to a series of thin-bedded sandstones and shales 
which correspond to the Gunnison formation of Mr. Eldridge’ and which 
have been by him assigned to late Juratrias time. No fossils have been found 
in this red sandstone formation, for the conditions of deposition were not 
'Geologic Atlas U. S., folio 9, Anthracite-Crested Butte, Colorado, 1894. 
