242 C. L. HERRI CK 



feet of silicious shale capped with quartzite, and 15 feet of similar 

 shales also capped with about 5 feet of quartzite. This is all that 

 remains of the great Sandia beds at this place, but to the east, on the 

 other side of the third granite mass, the series is complete. This 

 occurrence may be termed the " Incarnacion " fire clay, and the same 

 name will apply to the granite exposure, it being the name of the 

 mining district in which these exposures occur. 



There would seem to be no reason for separating the fire clay from 

 the Sandia formation, it being but a local variation, and, even where 

 the clay is not found, obscure plant remains attest the similarity of 

 conditions to some extent.' 



The Cane Spring fault area. — In this connection it may be desira- 

 ble to call attention to this profound dislocation, the exact nature of 

 which varies from point to point, but which is apparently found at a 

 distance of a mile or more to the west of the main escarpment of the 

 Cibola ridge. It lies nearly midway between the Incarnacion gran- 

 ite ribs, with their faults, and the main range just mentioned. The 

 typical exposure is, however, at "Ojo de las cafias," or Cane Spring, 

 a permanent water in the large arroyo joining the Rio Grande imme- 

 diately south of Socorro and owing its existence to the faulted area. 

 A section extending from the fault to the Cibola ridge is given, the 

 data being approximate, but sufficient to give some idea of the condi- 

 tions. 



The disturbance is profound and has the appearance of being a 

 double anticline with an interval separating the two members of some 

 eighth of a mile. At Cane Spring, where the disturbance is most 

 easily seen, about 700 feet of red, green, and yellow sandstone, shale, 

 and marl are tilted up at a high angle, with the appearance of an 

 appressed fold, the dip being to the west on the west side and to the 

 east on the opposite side of the axis. The western limb is concealed by 

 a covering of Tertiary, but on the east is a sharp fault, against which 

 the nearly horizontal strata abut with little inclination. Thence 

 eastward there are exposed by the arroyo about 100 feet of red and 

 yellow sand and marl to the second break, which is very similar to the 



I Since writing the above, similar plant remains {Lepidodendron sp., same as 

 Fig. 9 below) have been found in the lower part of the Sandia series on the west side 

 of the Ladrones Mountains, where the Sandia quartzite reposes directly upon the 

 metamorphic rocks (schists and granites). 



