GEOLOGY AND PALEONTOLOGY OP THE CANAL ZONE. 531 



weakness and mobility and are one of the factors that have caused 

 maximum sliding in this formation. In contrast with the clays of 

 the Culebra formation, these rocks are massive, largely of terrestrial 

 origin, contain little organic matter outside of the few lignitic shale 

 beds mentioned, have a greenish color from a high chlorite content, 

 and are much more given to sliding than the other rocks. 



EMPERADOR LIMESTONE. 



The Emperador is a light-colored, fairly pure limestone. It lies 

 unconformable on several of the older beds. Its outcrops are 

 comparatively small and weather locally into a pitted and platy 

 condition. Near Las Cascadas a section cut by the canal shows the 

 limstone, about 25 feet thick, overlying the upper part of the 

 Culebra formation. It outcrops northwest of Empire, south of 

 Las Cascadas, on the new line of the Panama Railroad near San 

 Pablo, near Frijoles, in the swamp southeast of Diablo Ridge, and 

 extensively near Alhajuela. 



CAIMITO FORMATION. 



The Caimito formation, which overlies the Emperador limestone, 

 consists of three members, as follows: (a) A basal light-gray, soft, 

 argillaceous, or clay-like, sandstone, which grades upward into a 

 yellowish argillitic sandstone that is bluish gray on fresh fracture; 

 (h) a peculiarly calcareous conglomerate with some fragments of 

 much decayed basic rock, which locally give a bright-green stain to 

 small patches of the formation; (c) a light-colored to yellowish argil- 

 laceous sandstone fairly well bedded. The upper argillitic sandstone 

 is the rock that outcrops in the Chagres River at Barbacoas, near 

 San Pablo. Beds a, h, and c may be seen in the section at Bald Hill, 

 north of Miraflores. Bed h outcrops extensively at San Pablo and 

 near the site of the proposed wireless telegraph station opposite 

 San Pablo.- The formation does not outcrop at all in Gaillard Cut. 



Miocene. 



GATUN FORMATION. 



The Gatun formation consists of three members, as follows: 

 (a) About 500 feet of marls and argillites, or clay rocks, and some 

 beds of soft sandstone and conglomerate; this member is bluish 

 gray but locally contains many brown specks, indicating fragments 

 of organic material; it is rich in the fossil shells of ancient marine 

 life; (b) mostly fine, soft sandstone, about 100 feet thick, containing 

 a few fossils; (c) light to creamy gray indurated clay beds. 



The formation is extensive and constitutes the foundation on 

 which the Gatun Locks are built. Fortunately, its fineness of grain 

 renders it relatively impervious to ground water. The upper part 



