714 INDEX TO THE STRATIGRAPHY OF NORTH AMERICA. 



from the Empire limestone. Only the foraminiferal portion seems to have been determined, 

 and these are regarded by Bagg as probably Eocene. The fossiliferous beds near Pedro Miguel 

 are undoubtedly at or very near the top of the formation, since the dip carries them below 

 the surface a short distance to the south, and borings at kilometer 59, slightly to the north, 

 show the usual Culebra formation extending to an unknown depth below. The Eocene and 

 Oligocene ages of the beds at the two locahties at Pedro Miguel seem certain. In any event 

 there can be little doubt of the Eocene age of the Culebra formation as a whole and its probable 

 correlation with the Boliio and Vamos Vamos beds. The occurrence of an Ohgocene fauna 

 directly above the characteristic Eocene at Pedro Miguel is comparable to the sudden change 

 that takes place at Gatun from the Eocene of the Vamos Vamos beds to the Oligocene of the 

 Gatun formation. 



The thickness of the Culebra formation has been variously estimated at from 400 to 500 

 feet. A boring made at kilometer 55 of the canal (hole 31) extends 40 feet below sea level, 

 starting at 167 feet above the sea; 207 feet of Culebra beds are here indicated, while possibly 

 175 feet might be added as representing the part already excavated at the cut, giving a thickness 

 of nearly 400 feet, with the bottom not yet shown. 



C 20. TRINIDAD. 



Wall ^nd Sawkins *°^^ distinguished the Newer Parian group in Trinidad as 

 Tertiary and recognized five divisions. They say: 



The Newer Parian group comprises a considerable succession of limestones, calcareous 

 sands, shales, loose ferruginous sands, conglomerates, clays, and marls, which seem sufficiently 

 related to one another by fossiliferous contents to form one group, of which the organic remains 

 present a certain analogy with the Miocene fauna. 



For distinct classification, five divisions or series are admitted, in naming which the same 

 principle of locality already employed, and so convenient in provisional nomenclature, will be 

 again adopted. These divisions are — 



A. The Nariva series. 



B. The Naparima marl. 



C. The Tamana or calcareous series. 



D. The Caroni or carbonaceous series. 



E. The Moruga or arenaceous series. 



The Nariva series consists of clays, with shales and extremely rare yellowish limestones, 

 and forms the substrata to the well-known red soils. * * * Thg strata are traversed by 

 bands of highly ferruginous matter parallel with the stratification. 



The geological importance of these beds is very subordinate; they possess, probably, but a 

 slight thickness and seem to constitute merely the inferior portion of the following division. 

 Their relations to the Older Parian group were not ascertained, and generally, from the absence 

 of proper sections, but httle information has been obtained respecting this series. * * * 



The Naparima marl includes a series of strata composed of marls, conglomerates, and 

 calcareous sand. 



The mineral matter of these marls is in a state of fine division and varies from a basis of 

 clay, with 10 to 50 per cent of carbonate of lime, to a basis of siliceous substance, consisting 

 of the shields of Infusoriae, and an average content of 20. per cent carbonate of hme. The 

 clay marl contains sometimes a much smaller proportion of Infusorise. 



There is generally a small proportion of carbonate of magnesia, and in some cases even 

 30 per cent, almost sufficient to combine with the carbonate of lime to form true dolomite. 

 * * * These strata have usually^ a highly conchoidal fracture, especially the more argilla- 

 ceous marls. 



The conglomerates are formed of rounded pebbles of indurated sandstone, and varieties of 

 jasper from the Older Parian, with cement. They do not exceed 8 or 10 feet thick and are 

 sometimes bounded by sands containing shelly fragments and a variety of calcareous matter. 



