MARSTERS, PHYSIOGRAPHY OF THE PERUVIAN ANDES 247 



and the West Cordillera, we have a comparatively narrow valley running 

 parallel with the West Eange. It is drained by the Eiver Huaraz, occu- 

 pying a longitudinal position throughout some three provinces, and finally 

 in the Province of Pallasca turning to the west to join the Santa, which 

 empties into the . Pacific. 



Continuing our section to the east from Huaraz we find in the place of 

 the deeply dissected intercordilleran plain another range of enormous 

 proportions .and running parallel with the one already described. It 

 reaches elevations of more than 20,000 feet at various points. From its 

 east slope, however, we now see the much-dissected Intercordilleran Belt 

 extending to the valley of the Marafion, a distance of perhaps seventy 

 miles. We thus have in this section two ranges on the west side of the 

 Intercordilleran Belt, instead of one, as in other sections noted; further, 

 instead of an intercordilleran lowland, as noted in the Cerro de Pasco sec- 

 tion, we have a deeply dissected belt whose uppermost surface has a 

 marked descent towards the valley of the Marahon. To the east of the 

 Marafion, we again have a somewhat softened expression of a continuation 

 of the East Cordillera. 



Let us now consider the position of the Marahon drainage system. It 

 heads to the south in the Department of Junin in a collection of lakes 

 within the limits of the Intercordilleran Belt. Following the main line 

 of drainage, we find that it, like many others, skirts the east edge of the 

 intercordilleran highland for many miles to the north, and finally, in the 

 Department of Amazonas, turns east to join the Amazon system, of which 

 it is an important member. Note again the longitudinal position of the 

 Marafion with reference to the geographical provinces as outlined. 



To the east of the valley of the Marafion, the Eaimondi maps show a 

 fairly well developed range separating the drainage of the Huallaga from 

 its western neighbor. Just what this range is, geologically, is unknown 

 to the writer, but it is believed to correspond to the East Cordillera. 



Piura-Huangabamba Section. — To the east of the Piura-Salitral Eiver 

 the long western slope is absent, and we encounter immediately the con- 

 tinuation of the West Eange with a rather abrupt slope, though softened 

 in its topographic expression, as compared with sections to the south. 

 This is followed by the intercordilleran highland, already thoroughly cut 

 to pieces by parts of two systems of drainage. The section of the Inter- 

 cordilleran Belt between Huangabamba on the north and Chota on the 

 south is drained by the rivers Huangabamba and Chotana. These be- 

 come confluent in the river Chamaya, which empties into the Marafion. 

 Note again the longitudinal position of the Huangabamba and Chotana 

 rivers with reference to our geographical provinces, while the Chamaya is 

 typically transverse in position. 



