86 The American Geologist. February, loos. 
They are usually horizontal, but west of Jemez Pueblo, dip 
slightly to the north. Their bluff formations weather down 
into cones and castled buttcs. They give a picturesqueness to 
the valley. Pleistocene deposits cover these in the valley. 
The Albuquerque Marls. — The Pliocene rocks in the Rio 
Grande embayment which are identical with the Jemez marls, 
just described, will here be called the Albuquerque marls. 
These marls are a continuation of the Santa Fe marls of Cope, 
a part of which was identified by him when at Algodones in 
the seventies. It also corresponds to the Loup Fork epoch 
(Tertiary) according to that geologist. ^" They are 350 feet 
thick at Albuquerque but thin out toward the San Dias. The 
upper stratum except the last, is a conglomerate series, the last 
is 5 to 10 feet of a curious yellowish white marl. The compo- 
sition of this marl is: Si02, 26.53; FcoOg, 1.20; CaCog, 64.47.^^ 
The Albuquerque marls are covered for the most part with 
later deposits, usually not more than ten feet in thickness. 
They will be mentioned later under "Pliocene Deposits." 
The Pleistocene Deposits. 
Pleistocene deposits are found in patches throughout the 
entire area visited. One small patch is situated at the foot 
and south of the Nacimiento 4nountains. Another patch oc- 
cupies the upper valley of Vallecieto creek at Vallecieto Viejo. 
Several patches are found between the hills on the road to 
Tejon and Placita near the Indian village of San Felipe. A 
large area occupies the inner valley of the Jemez river from 
Canon de los Jemez to the Bernalillo volcanoes, and extends 
more than eight miles up Salt river from' its confluence with 
the Jemez. A still larger area is found in the inner valley of 
the Rio Grande for many miles both above and below Albu- 
querque. These latter mentioned deposits may be designated 
as the "Rio Grande Marl." 
Jack Rabbit Valley. — The Pleistocene area at the foot of 
the Nacimiento mountains is about the size of two sections of 
land. It is the site of a Pliestocene lake. Its deposits are adobe 
clay and gravel overlying a granite floor. This area is called 
Jack Rabbit valley. 
Vallecieto Viejo. — In the Vallecieto Viejo area the Pleisto- 
cene covers a half a township or more. The underlying strata 
of this deposit are cross bedded sands and gravels, some four 
