360 



Prof. J. Orton on the, Geological 



Eaisedbeach of conglomerate. 



Rugged barren hills of trarhy- 

 tie porphyry, and contorted 

 strata of Jurassic (?) lime- 

 stone with granite dykes. 



Rolling pajonals. 



- COAST RANGE. 



Porphyry, syenite, quartzite, 

 and conglomerate. 



fed 

 o 

 S 



sedimentary slopes of the Andes and the metamorphic regions 

 of the Casiquiare and Central Brazil. 



As the rise of the Andes was the creation of the Amazons, 

 the study of the mountain should precede that of the river ; 

 indeed the structure of the * 

 basin cannot be under- *% 

 stood without a knowledge 

 of the "rim." The geo- 

 logy of the Andes is not 

 sufficiently advanced to 

 warrant a classification 

 of the ranges with respect 

 to their periods of eleva- 

 tion. Yet it is very pro- 

 bable that the coast Cordil- 

 lera was the first to emerge, v 

 and very certain that the jj 

 eastern did not reach its ? 

 present elevation until 

 after the Cretaceous age. 

 The characteristic rocks 

 of the maritime range are j 

 trachytes and porphyries; ' 

 of the oriental, sandstones 

 and slates. 



The annexed profile of 

 the Andes of Northern j 

 Peru gives the relative '• 

 heights of the ranges and 

 the main formations. I 

 found no fossils in the 

 Pacasmayo beach ; but at 

 Pay ta, further north, there 

 are many — among them ( 

 Turritella patagonica, : 

 Sow. (which Darwin found 

 also on the coasts of 

 Patagonia and Chile), and 

 Pecten modisonus, Say, 

 and Crepidula formcata, 

 Say, identical with Mio- 

 cene species on the east 

 coast. The beach was 

 therefore raised in late or 

 post-Tertiary times; and 

 there is evidence that a 



Humboldt's red " freestone." 



' Sandstone. 



— Cretaceous limestone. 

 — maranon. 



— Granite and mica-schist. 

 CALLA-CALLA. 



— - Lias limestone. 

 Red sandstone. 



FISCOOUANUNA. 



Lias shale and sandstone. 



r- Slate and sandstone. 



^— PUNTA VENTANA. 



Limestone. 

 Triassic shales. 



.'."..PUNTA DE SCHALCA. 



Cretaceous limestone. 



.*".'."r*Slate and sandstone. 



'CERRO DE IOUTO. 



Saliferous red sandstone. 



Tertiary sands and clays. 



HUALLAGA RIVER. 



*2 



■5; 



