GEOLOGY AND PALEONTOLOGY OF THE CANAL ZONE. 533 



for localities at which fossils were collected. The numbers in italics are for the Canal 

 Commission stations. 



Section in canal cut 600 feet south of Miraflores Locks. 



Pleistocene: Feet thick. 



3. River alluvium with gravel and pebbles, loosely cemented 

 conglomerate at base, almost horizontally bedded, is 

 unconformable on (2), and has an exposed thickness of . . . 20 

 Unconformity. 

 Oligocene (Culebra formation): 



6009-2. Dark, soft, fairly well-laminated clay rock which 

 seems to be unconformable on (1), shows a few lines 

 of small limy concretions, buff-colored after weath- 

 ering, parallel to the bedding. This is a foraminif eral 

 clay and is the upper part of the lower beds of the 

 Culebra formation. Dip 12° southward. Thick- 

 ness exposed here 45 



Unconformity. 



Eocene (?) (Las Cascadas agglomerate (?)): 



1. Mottled, light-greenisb , tine-grained agglomerate to coarse 



tuff. The grains, one-eighth to 1 inch in diameter, are 

 soft irregular particles of basic mud rock or much altered 

 andesitic tuff. Finely divided chlorite seems to give 

 greenish color. The spaces between the grains are filled 

 with white limy cementing material, thus giving the 

 rock a whitish and light-green mottled appearance, 

 though the prevailing color is light green to grayish- 

 green. Rock very similar in appearance to this is ex- 

 posed in the upper part of the Contractors Hill mass, 

 and was noted in the bottom of the Gaillard Cut near 

 Paraiso, and near station 1909 where a small cave in the 

 rock was found. As this lithologically resembles the 

 Las Cascadas agglomerate and is distinctly different 

 from the typical Culebra formation, it is considered as 

 representing the upper part of the Las Cascadas agglom- 

 erate. Thickness exposed 15 



Section at Canal Commission station 2089 south of Miraflores Locks. 



Pleistocene: Feet thick. 



3. Siltand alluvium faulted down opposite (1), exposed about. . 30+ 

 Miocene (Panama formation): 



2. Light to buff-colored tuff beds showing some cross-bedding 



and some iron staining along the cracks, unconformable 



on (1), exposed about 15-f- 



Eocene (?) (Las Cascadas agglomerate): 



1. Massive basic agglomerate, much altered, mostly greenish 

 with some lighter-colored patches, giving a mottled color 

 effect; cut by basaltic dikes; contains a few little cracks, 

 some of which are filled with iron-stained cherty material. 

 Exposed about 304- 

 Th ere is at this place a fault which trends S. 15° E. and hades 

 80° W. It is impossible to estimate the amount of the throw, 

 because it is not known how much may have been eroded 

 from the upthrow side since faulting. In a few places along 



