CRETACEOUS FOSSILS—-ALLUVIAL DEPOSITES. 19 
colored, and the beds are from one to twenty feet thick. A thin argillaceous dolomite is found 
below them. Thus it is seen that the strata along this part of the route are mainly composed 
of marls and sandstones of various colors—the red predominating—and of intercalated gypsum 
with beds of argillaceous dolomite. The latter are, however, quite thin, the bed mentioned in 
the section being only six feet thick. These strata are in the main horizontal, but at some 
localities have inclinations of from 10° to 15°, the line of trend being nearly east and west. 
This angle of dip corresponds with those observed in the sandstones east of Delaware mount- 
ain, and it is probable that they may be referred to the same line or axis of elevation. Up- 
raised sandstone strata dipping at an angle of 30° to 40° were seen by Dr. Shumard several 
miles further west of these localities. It should also be observed that the Witchita mountains, 
which are composed of granite and greenstone, rise about forty miles southwest of Camp 31. 
Under date of September 1st, we find in Mr. Marcou's notes the following record: ‘ About 
two miles southwest of Camp No. 31 we find at the summit, and sometimes half way up the 
hills of red sandstone and clays, three or four broken beds and crinoids [?] disseminated here and 
there as if the ruins were formed of a lumachelle limestone of Neocomian age. This lumachelle 
is formed by the fragments of Ostrea aquila or Couloni, or a variety, for it is smaller.’’ ‘‘ It is 
possible to gather a quantity of this ostrea in a good state of preservation. I found also many 
small shells of Pecten quinque costatus and a debris of Terebratula."  ** Before coming to the 
lumachelle, which is in contact with the red argillaceous sandstone of the Trias, there is a 
greyish white calcareous sandstone, which passes to a white limestone slightly oolitic [?] 
then the lumachelle of ostrea." ‘‘ This bed of transition is only one foot thick ; the four beds 
of lumachelle are two feet." In the Resumé Mr. Marcou describes the formation as follows: 
“I have mentioned two points between Topofki creek and Anton Chico, where the Triassic 
rocks are covered by more modern formations; the first of these points is upon one of the 
tributaries of the Washita river, near our Camp No. 31, where, upon the heights, are found 
the remains of beds of a limestone filled with shells, which I connect with the Neocomian of 
Europe, or, in other words, with the lower division of the Cretaceous rocks. This limestone is 
only five feet thick ; it is of a whitish grey color, containing an immense quantity of ostracea, 
which I consider (provisionally) as the Exogyra pai Losa, Roemer ; having the closest analogy 
with the Exogyra of the Neocomian of the environs of Neuchatel.”” 
The only representative of this formation which I find in the collection, is the well known 
Cretaceous fossil Gryphea Pitcheri, No. 134 of the catalogue. This, indeed, is the only fossil I 
find in the collection brought from this section of the route. The gbsor vations i in regard to the 
extent of this deposite laterally are not very definite. In the Resumé, Mr. Marcou states, that 
it “has been almost wholly destroyed and carried away by denudations, for it is only found on 
the summits of the hills, resembling the remains of ancient buildings ; it occupies actually only 
the width of three or four miles." Captain Marcy, who passed over this region in 1849, men- 
tions a “formation of gypsum and blue limestone ledges, in which he discovered petrifactions 
of oysters and muscles." This is probably the same deposite, or a continuation of that seen by 
Mr. Marcou. It was between the Washita and Canadian rivers, near the sources of the former. 
Lieutenant Simpson observes, respecting this region, that up to a point “within twenty 
miles of the Antelope hills, the country is richly characterized by the gypsum formation; the 
evidences of which appear in outcrops all around. This mineral can here be found in almost 
every form—earthy, fibrous, selenitic, and massive; and it is doubtless owing to it that the 
water of the region co-extensive with it is in many places so unpalatable and nauseous.””* 
Alluvial deposites.—Mr. Marcou frequently refers to accumulations of round pebbles, which he 
calls alluvium, found along the route, and, as I understand by his notes, above the beds of the 
creeks. Between Camps 20 and 21, this ‘‘alluvium’’ was formed of quartz pebbles the size of 
& pigeon's egg. Between Camps 25 and 26, pebbles of quartz, trap, agate, and jasper were 
! Report on the route from Fort Smith to Santa Fé, p. 179. 
2 Report on the route to Santa Fé, p. 8. 
