MAR8TERS, PHYSIOGRAPHY OF THE PERUVIAN ANDES 235 



qua Valley and in the Cuesta de Mato de Caballo. Here is exposed a 

 series of somewhat coarse deposits on top, followed by a thick series of 

 clays and fine sands. Folding and faulting have taken place to a con- 

 siderable degree. 



The Pampa de Clemesi has an elevation near the Tambo Valley of 

 some 4,000 feet on its inner edge, but it descends in the direction of 

 Moquequa and Locumba. At the valley of Sama, which at present con- 

 stitutes the dividing line between Chile and Peru, the elevation at the 

 inner edge is not more than 800 to 1,000 feet. The same grouping of 

 sediments may be seen on the Sama as in the Moquequa Valley. 



As regards the character and distribution of the outliers,, a word must 

 be added. The pre-Tertiary coastal chain is persistently present from the 

 valley of Atico to the mouth of the valley of Sama. Near the valley of 

 the Tambo, the edge of the foothills practically joins the Cadena de la 

 Costa. It is for this reason that we have a number of small pampas 

 separated by a collection of outliers. In the stretch of coast from Mol- 

 lendo to Quilca and Camana, the coastal ridge is most prominent in its 

 topography and reaches a width of some kilometers. Their topographical 

 strength, however, gradually fades away in the direction of Sama. To 

 the south of this point, I am told, the ridge is replaced by a series of 

 morros, of which the historic morro at Arica is a good example. 



Original Tertiary Area. — At the present time we probably see but a 

 small portion of the original area of deposition of Tertiary time. The 

 Ba}^ of Guayaquil is very shallow and may represent a slightly depressed 

 part of the Zorritos-Tumbes plains. That Tertiary deposits extend some 

 distance to sea in front of the Zorritos-Nigritos shore line is more than 

 probable. This conclusion is borne out by the fact that, for many years 

 past, mariners have repeatedly reported the occurrence of oil patches on 

 the surface of the sea some miles out from the present shore line. 

 Further, such reports are not confined to this part of the coastal shelf, 

 for quite recently similar evidence has been noted in the region of the 

 Lobos Islands, located in front of Pacasmayo. In fact, so marked was the 

 evidence that parties of Lima have recently attempted to take up territory 

 on the above-mentioned islands, with a view to developing a petroleum 

 industry. 



So far as is known to the writer, petroleum-bearing formations of the 

 coast are confined to the Tertiary horizons. Even in the interior of Peru, 

 in the region of Lake Titicaca, there is every reason to believe that the 

 petroleum deposits of the Pusi section are likewise confined to the Ter- 

 tiary. 



