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AYXALS XEW YORK ACADEMY OF SCIENCES 



some 300 feet above sea level and with its shoreward edge somewhat cut 

 up by narrow, short valleys. Passing to the interior from Lobitos in the 

 direction of the Amotape spur of the west range of the Andes, consid- 

 ered in its broadest sense, the evidence of folding, faulting, etc., rapidly 

 disappears, until we approach the inner edge of the plain, where we find 

 that the Tertiary sediments are upturned. 



Following to the south towards Talara and Mgritos we find that while 

 folding is much less accentuated than at Lobitos, it by no means disap- 

 pears entirely. At Talara, however, we find another area of maximum 

 disturbance, which extends to the southern end of the oil field now being- 

 operated by the London Pacific Petroleum Company. Following this 

 section to the interior, we note, as in the preceding cases, a disappear- 

 ance of the folding, until we reach a narrow belt adjacent to the Amotape 

 Mountain, where the Tertiary strata are found to stand at a high angle 

 and dip toward the northwest. I Avish here to record another fact. The 

 first oil springs noted in this region were located at the interior edge of 

 the coastal plain at a point known as La Brea. A little later a residuum 

 of petroleum was located on the playa near Nigritos. This was mined for 

 some time by the Spaniards and prepared for painting the bottoms of. 

 their ships. 



In the Chira Valley, we find the Tertiary occupying an arm-like ex- 

 tension or depression between the Amotape spur on the northwest and 

 an edge of the foothills on the southeast. On the high plains to the rear 

 of Paita, some 300 feet above sea level, there is a well-defined noncon- 

 formity between red clays with a marked tilt and a series of sands and 

 conglomerates containing numerous fossils. Many of these resemble very 

 closely the forms now living on the present shore. At various points 

 between Paita and Piura there may be seen on the surface shells of 

 exactly the same variety as are now living on the Pacific shore. 



Just south of Paita we find a typical outlier of the western range stick- 

 ing its higher points somewhat above the level of the adjacent plain. 

 In the interior, the eastern boundary is located near Tambo Grande. It 

 follows the general trend of the rivers Salitral and Serran (or E. Piura), 

 or not far from the contact of the coastal plain deposits with the pre- 

 Tertiary formations of the foothills. That is to say, the Salitral-Serran 

 valley has been made by a longitudinal subsequent river, using the phrase- 

 ology of Professor Davis. 



The maximum width of this division of the coastal plain is attained 

 along a line from Cerro de Yllesca to Salitral. Following the inner edge, 

 we pass to the south through Olmos, Motupe, Patope and Cayalti. A very 

 narrow belt then passes along the present shore line to the Pacasmayo 



