258 ANNALS NEW YORK ACADEMY OF SCIENCES 



Within the Titicaca basin, we have an additional occurrence which so 

 far is not known to occur anywhere in the northwest extension of the 

 Intercordilleran Belt. In this basin, there is a considerable series of 

 sediments deposited upon limestones which are regarded as Cretaceous. 

 The former are probably Tertiary. They contain petroleum, but devel- 

 opment work has not been carried far enough to determine the areal extent 

 of the oil sands. The only work of any moment has been done by the 

 Titicaca Oil Company, backed by California people. Work has been 

 suspended for the present. 



The gold-bearing veins of Poti as well as those of the Santo Domingo 

 region to the east from Tiripata are associated with the erupt ives and 

 older sedimentaries of the East Cordillera. 



It is also known that the region of Huanaco, to the north of Cerro de 

 Pasco, is highly mineralized. From data at hand it would seem that the 

 geological associations are similar to those of Santo Domingo. 



In the region of Huaraz and Eecuay (valley of the Huaraz) there 

 exists another mineralized belt containing silver, copper and gold ores, 

 as well as lead ores. It is quite undeveloped. These are associated with 

 intrusives of the West Cordillera. 



Iron, copper and silver ores also occur in the West Cordillera, to the 

 northeast of Piura. They are associated with dioritic intrusions and 

 bosses in the midst of a heavy series of shales and sandstones. 



Resume 



In the Andes of Peru, we can easily recognize a series of parallel and 

 well-defined physiographic provinces, which in the larger sense are defi- 

 nitely related to the geological development of the Andean Eange as a 

 whole. 



Whatever has been the succession of physiographic changes in the 

 development of the Andes as a unit, there has evidently taken place, at 

 least on broad lines, a marked adjustment of drainage to structure, thus 

 affording a longitudinal and transverse arrangement, or pattern, such as 

 may be easily recognized in many other continental mountain systems. 



A comparison of observed and recorded facts with reference to the 

 occurrence of ore-boclies in Peru proves that they are generally associated 

 with contact phenomena. 



