Hkrshey 



Isthmus of Panama. 



247 



and continuance of eruptions along volcanic range (Veraguas foot- 

 hills belt and Culebra region). 



4. The Claiborne epoch of sedimentation on Atlantic side. 



This classification of the volcanic formations brings the Santiago 

 formation precisely in the latter portion of the Cretaceous period, 

 where we provisionally placed it because of its remarkable resem- 

 blence to the Chico formation of California, and seems to indorse 

 our tentative correlations down to the very lowest formation. 



The Cailazas Formation. — The village of Cahazas is situated in 

 the foot-hills belt in the midst of mountains composed of the Pan- 

 ama series of volcanics. Beginning at about one mile east of the 

 village, there is a small area, several miles in diameter, of finely 

 laminated light gray and brown shale. It is evidently composed 

 of volcanic ash which was deposited in a body of water, probably 

 a small lake. There are slight traces of fossils. In the midst 

 of the shale is a three-foot stratum of coarse volcanic ash, repre- 

 senting apparently a single shower. On the eastern and northern 

 sides of the area, a coarse basal conglomerate composed of 

 water-worn boulders of the lower portion of the volcanic series, is 

 developed to a thickness of 50 to 100 feet. The formation dips 

 southward io° to 30 , having been concerned in the orographic 

 movement which lifted the Cordillera de Veraguas. It is evident 

 from the way in which the Cailazas formation is included in the 

 Panama series that it represents local conditions — merely a lake of 

 short duration in which was deposited several hundred feet in thick- 

 ness of finely laminated tuff or shale. Its age is, therefore, prob- 

 ably Eocene. 



The Veraguas Crystalline Scries. — The Cordillera de Veraguas, 

 where I crossed it on the line of the old Santa Fe and Cocuya 

 trail, about 120 miles west of Panama, is an immense igneous mass, 

 probably 25 miles in width and attaining an altitude of 5,000 feet 

 above the sea. It is made up of three rock types, specimens of 

 which were submitted to Dr. U. S. Grant, who determined them. 

 In the valley of the Rio Santa Maria on the southern slope 

 of the range, the formation is mainly a rather coarsely crystal- 

 line plutonic rock of light yellowish gray color. With its abundant 

 free quartz, it somewhat resembles a true granite on outcrop. The 



