104 Bulletin of Lcibomtories of Denison University 
is probably Jura-triassic. Passing south, there are low hills with 
gypsiferous shales and gray and white sandstones nearly to La 
Madera which seems to be upon a plateau of limestone, broken 
in places by granite or other igneous rocks. From San Anto- 
nio to San Antonio is a Cretaceous region and along the road- 
side we find about 50 feet of shales with lenticular masses of 
limestone topped by an eqal amount of freestone. Between 
San Antonio and Tijeras the boundary between the Cretaceous 
and the Jura-triassic is crossed through here the disturbed strat- 
igraphy is difficult to unravel. The valley of the creek from 
“ Uno de Gato ” to Alamillo and southward is occupied by the 
red Jura-triassic. Ascending the creek we encounter horizon- 
tally stratified beds of clay possibly of Pleistocene age reposing 
on older tilted rocks. 
4 . 
CARBONIFEROUS AREA SOUTH OE TiJERAS. 
On the east side of the range, south of the town of Tijeras 
is a region consisting chiefly of rough and rolling country quite 
densely timbered. Passing south of Tijeras, which is situated 
on the Jura-trias area, about half a mile, the contact between 
the Jurassic red sandstone and the Carboniferous limestone is 
clearly seen. The contact is along a sharp fault extending ap- 
proximately east and west — a line which may be followed at 
intervals for many miles. The upturned edge and adjacent parts 
of the lime are metamorphosed and filled with segregated silica. 
The dip is to the southwest in the immediate vicinity of the 
fault while the Jura-triassic on the opposite side dips northeast. 
To the south of this fault the country is wholly made up of 
Carboniferous strata. The series is nearly horizontal with slight 
variation in different directions from the horizontal plane. 
Although there seems to be no place where the entire Car- 
boniferous series is exposed from bottom to top the following 
section is no doubt nearly complete and embraces over 600 feet 
commencing with dark fossiliferous limestones such as are else- 
where found near the base of the series. The fossils are such 
