78 The American Geologist. February. 1903. 
for various purposes. They burn it and then whitewash their 
houses with it. 
Several gypsum-capped patches, each of small area, flank 
the Nacimiento mountains on the west. They were islands 
or isthmuses in Cretaceous time, as they are all entirely or 
nearly entirely surrounded with Cretaceous deposits. 
The gypsum-capped area southeast of Jemez Pueblo is a 
still smaller one, not more thian five acres being exposed. It 
is surrounded on all sides by Tertiary beds, which indicate that 
it remained an island even to the close of the Tertiary period. 
The strata of this area dip northeast. 
To the northeast of Tejon there are several gypsum patches. 
They all occupy valley positions, all are small, and the strata 
of each dip east at an angle of 40'^. They may cap the Red 
Beds series there, but the strata are too much broken to give 
anything definite on the subject. The easternmost of these 
patches dips under the Cretaceous, which will receive atten- 
tion later. 
Age of the Gypsum. — The gypsum series here described 
occupies a position between the Red Beds and the Cretaceous. 
By some geologists it has been correlated with the Red Beds, 
and the whole called Juratrias. By others it has been desig- 
nated as the gypsum series and left at that. But Cope, who 
visited the section north, of the Jemez plateau, has called it Jur- 
assic ; and in speaking of the gypsum series at Canyon Caugi- 
lon, he says : "The gypsum is that usually referred to the 
Jurassic — ...and doubtless inseparable from the brilliantly 
colored beds below which are stated by Hayden to be Jur- 
assic."* 
The Cretaceous Strata. 
In this paper the writer will consider the Fort 
Union beds and the Puerco marls as Cretaceous for 
reasons which will be given later. He will then have west 
of the Nacimiento mountains 1000 feet of Puerco marls at the 
hiead waters of Salt river. Just south of these marls the Fox 
Hills comes in, and continues from the Jemez group of moun- 
tains near Jemez peak in a curve to a point below Cabizon on 
the east side of the Rio Puerco. They also extend west of that 
river farther than was visited. They are covered with later 
deposits west of Cabizon. South of the Fox Hills east of Cab- 
