Jcmc^ — Albuquerque, N. Mex. — Reagan. 89 
at Placita, which Cope has identified as Pleistocene, are found 
to be Pleistocene in age. 
Under what conditions these deposits were laid down need 
not be conjectured; the proof is at hand. After the river had 
cut its channel deep into the Tertiary from Cafion de los Jemez 
to the then wide valley of the Rio Grande, the Bernalillo vol- 
canoes became active, and the lava flow filled up the channel in 
its lower course. This channel occupied the ^ame site as the 
present one ; but was much larger as is seen by the lava walls 
in the old trough on each side of the present river. Contem- 
poraneous with this eruption, there was a shifting of the strata 
beneath the river bed as is very noticeable in the vicinity of the 
above volcanoes. A lake of considerable size was formed in 
which the beach sands were laid down, which today make that 
region a desert waste. This lake continued to exist till the 
lava dam at the east was cut out, and an outlet into the Rio 
Grande again established. Since then the re-adjusting of the 
strata has greatly elevated the deposits on the north. 
The Rio Grande Marls. — The Rio Grande marls extend up 
and down the river for many miles both above and below Al- 
buquerque. At the village of San Felipe the inner valley is 
wedged in ; and for a short distance these deposits cease, only 
to appear again at Thornton and on the north. They are cross- 
bedded, permiscuously deposited, loose sands and gravels in- 
terstratified with bands of clay, the whole of which is over- 
lain with an adobe deposit. The thickness reaches some 20 
feet or more at a point just west of Albuquerque where ex- 
cavations have been made to recover the supposed buried treas- 
ures of the Spanish people. Beneath the Rio Grande Marls 
were found the conglomerate beds which underlie the Jemez 
and Placita deposits. This seems to indicate that these marls 
belong to the same age. 
The Age of the Rio Grande Deposits. — In the marls about 
Albuquerque undecayed wood bias been found many feet be- 
neath the surface ; and in the same deposits at Paiia Blanco 
were found the teeth and bones of the Elephas primigenius 
and other Pleistocene animals which strongly suggest that these 
deposits are of Pleistocene age. But even if no animal remains 
had been found, their age could still be determined. They are not 
only identical with the Placita dci:)Osits in most respects but are 
