GEOLOGICAL REPORT. 279 



noticed heavy masses of brick-red, soft sandstones in connection witli the Carbonifer- 

 ous rocks of the Rocky Mountains, which I consider as much older than the beds Xos. 

 13 and 14, and the lithological similarity alone is a very deceptive evidence of the 

 contemporariness of the formation. I have not observed gvpsuni with these, but the 

 gypsum is in many instances a secondary formation, which did not originally exist in 

 the rocks where it now occurs, and may, therefore, be found in formations of every ago. 



Thus far we have no positive evidence of the age of Xos. 13 and 14 of the above 

 section. Such formations contain usually few organic remains, either because the chem- 

 ical properties of the acid waters in which they may have been deposited did not favor 

 the existence of animal life, or because their traces were obliterated subsequently by 

 chemical agencies connected with the formation of the gypsum. I only found in them 

 the impression of what appears to be the sheath (ochrea) of a leaf, such as is, to mv 

 knowledge, not known in the Paleozoic era, and is first observed with plants of the 

 Triassic epoch. At the points where I noticed these strata, thev are closely connected 

 with Jurassic rocks. 



At La Bonte Creek, where the formations underlying them are largely developed, 

 there appears to be a very considerable thickness of strata between them and the lime- 

 stones of the Carboniferous period, of which I have spoken above, and which is com- 

 posed chiefly, as far as we could ascertain, of sandstones of white, gray, and In-own 

 brick-red, and purple colors, the latter mostly soft shalv, with intorstratifications of 

 variegated shales and slates. Not having had sufficient time for more extended exam- 

 inations in that interesting locality, where the stratification is much disturbed by local 

 upheavals, I dare not express a. decided opinion in regard to the age of this apparently 

 intervening series. I am inclined to think that we have there Permian or Triassic 

 rocks, not observed before developed in a similar degree and with the same features. 



An additional evidence of the probably Triassic age of Xos. 13 and 14 is found in 

 the large development of similar gypsum-bearing areno-argillaceous formations further 

 south, in Northern Texas Juid New Mexico, where the}' also underlie Cretaceous beds, as 

 stated by Mr. Marcou, Dr. G. Shumard, Mr. Blake, in the reports of Captain Marey, 

 Captain Pope, Captain Whipple, and others, and in the interesting discoveries made 

 along the Great Colorado and its tributaries by Dr. Newberry, on the expeditions under 

 Lieutenant Ives, Topographical Engineers, in 1858, and Captain Macomb, Topograph- 

 ical Engineers, in 1859. Dr. Newberry there discovered in such formations some 

 plants of the genera Zauiitrs, I'< trnpliilhim, &<:., and Saurian bones, which led him also 

 to refer this series to the Triassic epoch. (See American Journal, vol. 28, second 

 series, page 299.) Similar formations are largely developed in the southern part of 

 the Wahsatch Mountains. (See section IV.) 



The gypsum evidently existed as such before the eruption of the green-tones. 

 On La Bonte' Creek, where the irregularity of the stratification is caused by intrusions 

 of the greenstone, 1 observed that a thick bed of gypsum, which is considerably bent, 

 has thereby been broken and brcceiated, and exhibits numerous tissures radial to the 

 curvature. 



In connection with the Triassic formation, I have observed some very instructive 

 instances of complicated stratification, produced by the combined eilects of multifari- 

 ous upheavals. 



