vAruHAN.] NOTES ON SAN CARLOS SECTIONS. 83 
GEOGRAPHIC DISTRIBUTION OF QUARTZ-PANTELLERITE. 
From the peak (> miles west of south from Chispa one can, upon 
looking east, see a very thick sheet of rock above the rocks which form 
the peak. Going south along Van Horn arroyo, this sheet can be 
traced with the eye, and is seen to form the top of the mountain the 
entire distance to San Carlos. Messrs. Bassett and Chapman, who 
during the field season of 1895 made the San Carlos topographic 
sheet, noticed this peculiar rock, and have furnished additional obser- 
vations in regard to its distribution. It extends south and east of San 
Carlos for many miles. (PL VIII.) As the area covered by the pan- 
tellerite has not been mapped geologically, it is not possible to state 
what extent of territory was originally covered by that enormous sheet, 
but from present knowledge it was certainly many hundred, possibly 
several thousand, square miles. 
CORRELATION OF THE CHISPA AND SAN CARLOS SECTIONS. 
So great a variety of volcanic products as was observed south of 
Chispa was not seen at San Carlos, but taking the pantellerite and the 
rocks immediately underlying it as starting points for a comparison, 
there can be no doubt that all of the section studied in the peak south 
of Chispa is above the coal horizon. The beds at Gettysburg Peak, 
near San Carlos, from and including the conglomerate bed to the base 
of the pantellerite, certainly represent, in part at least, the Vieja series. 
The stratigraphic relations existing between the Vieja series and the 
underlying San Carlos beds were not discovered. Whether two series 
of beds are comformable or are separated by an unconformity was not 
ascertained. 
TIME OF THE VOLCANIC OUTBURSTS. 
Dumble, 1 in his paper on the Cretaceous of Western Texas and Coa- 
huila, Mexico, states: "Since no erosion was observed in the bed 
immediately underlying the first lava now, this lava of the Vieja Moun- 
tain is * * * seemingly of Ponderosa age." It may be true that 
the outbursts occurred during the time in which the Taylor {Exogyra 
vonderosa) marls were deposited, but neither Dumble's nor our own 
observations were sufficiently extensive to solve the problem. It should 
be stated that the interbedded fragmental rhyolitesand sediments have 
been subjected to orogenic movements, showing that the faulting and 
folding have taken place since volcanic activity ceased. 
DIKES. 
Two systems of dikes were noted, as pointed out by Dumble. As 
10 collection of the dike rocks was made, this subject is passed without 
farther remarks. 
iBull. Geol. Soc. America, Vol. VI, p. 387. 
