MAR8TER8, PHYSIOGRAPHY OF THE PERUVIAN 7 ANDES 253 



named. From the valley of Chorunga to Andara} r , the dioritic forma- 

 tions constitute the principal formation. Ascending the highland above 

 Andaray, we again find a broad plain extending away to the southeast in 

 the direction of Chuquibamba. The plain is composed of the same sort 

 of mud flow as we have seen on the inner escarpment of the Coastal 

 Plain overlooking the Chorunga -Valley. Through this protrude various 

 knobs of diorite, the same horizon as we saw in the trail from Chorunga 

 to Andaray. Into this plain the west tributary of the Majas Eiver .has 

 cut a deep valley not only through the mud flow, but well into the under- 

 lying crystallines. On this floor rests the city of Chuquibamba. 



Continuing our course to the north and northeast, we come finally to 

 the edge of the lava flows forming a veritable platform on which were 

 built the four confluent domes of the Cora Puno composed of lava, ash 

 and scoria. A very large part of their slopes is above permanent snow 

 line. These domes undoubtedly surpass 20,000 feet in altitude. From 

 the northeast slope of Cora Puno we have before us a gently ascending 

 plain, with eerros appearing here and there above the general sk} r line. 

 Among these are the majestic Solamana, Leon Wachang and others with 

 unpronounceable Indian names. And here let me say, if any enthusiastic- 

 mountain climber wishes to test his real ability, he should not miss trying 

 the spires of Solamana. The plains between the peaks are, in part, at 

 least, made up of a light-colored mud flow, lithologically the same as that 

 seen on the other side of Cora Puno and the inner edge of the Coastal 

 Plain or the Iquipi cuesta. Occasional small knobs of limestone protrude 

 through this sheet. Also, where some of the streams have cut to any 

 great depth, we sometimes find limestone exposures. That is to say, the 

 light-colored lavas, the dark basal lava platform and the superimposed 

 cones of Cora Puno, probably rest upon a floor of limestone on the north- 

 east and dioritic crystallines on the southwest of Cora Puno. Such of 

 the smaller spire-like hills as were examined were found to be volcanic. 



In a word, then, comparing our sections, we shall find that we have a 

 similar succession and order, with the exception that in the Huacho-Oyon 

 case the Coastal Plain is absent. Physiographically, Cora Puno and the 

 series of snow-covered domes to the southeast and northwest are situated 

 well up the West Slope and not far from the West Cordillera. The im- 

 portant mining camp, Caylloma, is located on the east slope of the West 

 Cordillera, into which the headwaters of the Apurimac are now cutting 

 their way. 



To the northeast from Caylloma to the Cuzco region we have the broad- 

 ened Intercordilleran Belt, literally cut to pieces by the labyrinth of val- 

 leys occupied by the various tributaries of Apurimac and the Villcanote. 



