734 



JOHN W. GRUNER 



describe these occurrences in detail, but as a rule sheeting in these 

 rocks has a steep westerly to northwesterly dip. Nowhere in the 

 ancient rocks were any close folds or signs of distortion and twisting 

 seen, as might be expected in schists, and as were actually observed 

 in the metamorphosed sedimentary rocks described below. 



Granitic gneisses occupy a rather obscure position with respect 

 to the more basic varieties, and may, in some cases, be of the same 

 age as the batholithic granite intruding the older schists. In one 

 instance, on Old Mike, this relationship was proved. Here the 

 gneiss could be traced to its parent rock, the granite beneath. 



The following outcrop deserves special attention in the opinion 

 of the writer. The plateau south of Lucero Peak, between the 

 Salazar and Lucero Canyon, is covered with a dark-green, fine- 

 grained hornblendite and greenstone which resemble a flow. A 

 "sheet" at least 200 to 300 feet thick, of dark, indistinctly schistose 

 rock, overhes the granitic batholith. Ramifying apophyses from 

 the granite beneath can be seen in the greenstone. Just north of 

 Lew Wallace Peak lies a relatively small mass of greenish-gray, 

 very fine-grained altered diabase. No cleavage or regular sheeting 

 is visible in it. Whether this rock bears any genetic relation to the 

 sheet on the opposite side of Lucero Canyon, just described, or not 

 could not be determined. 



Metamorphosed sedimentary rocks. — The metamorphosed pre- 

 Cambrian sediments occupy belts of greatly varying width between 

 the Pennsylvanian series on the southeast and the granite batholith 

 on the northwest. The assumption that the batholithic granites 

 are younger than the metamorphosed sediments is based upon the 

 attitude of these formations, which flank and abut against the 

 gneisses and granites. (See Fig. 2.) The formations are chiefly 

 composed of quartzites and quartz and chlorite schists, and are 

 undoubtedly of sedimentary origin. 



The area of quartzite as outhned on the map claims accuracy 

 only along the western margin. The eastern limit could only be 

 estimated; therefore the outcrop may be somewhat narrower. 

 The dip of the quartzite is steeply eastward, varying from 45° to 

 90°. Jointing at right angles to the beds is the rule. Figure 3 

 shows a nearly perpendicular exposure of quartzite, 300 feet high, 



