584 INDEX TO THE STRATIGRAPHY OF NORTH AMERICA. 



In describing the Cretaceous limestone Sievers refers to classifications by Wall 

 and Steinmann. He cites three divisions of the Older Parian group, so named by 

 Wall in his "Geology of the Island of Trinidad," and finds a parallel with divisions 

 recognized by him in the Cordillera de Merida. 



Referring to a report contributed by Prof. Steinmann on the fossils which 

 Sievers had collected Sievers says: 



Steinmann infers that there are three limestone formations which may be distinguished — 

 (a) the dark bituminous limestones of San Cristobal, with Exogyra ; (b) the succeeding Barba- 

 coas formation, with many ammonites; and (c), still higher, the broad crystalline limestone 

 with many poorly preserved fossils of Exogyra, Trigonia, Cardita, and Astarte, which occur 

 extensively in northern South America. Of these formations the age of the Barbacoas alone 

 can be determined accurately. It belongs to the Upper Albien, on the boundary between the 

 Lower and the Upper Cretaceous, and is distinguished by the following fossils: 



Schlcenbachia inflata Sow. 

 S. varicosa Sow. 

 S. belknapi Marcou. 

 Hoplitea tocuyensis. 

 Mojsisovicsia durfeldi Steinmann. 

 Cardium peregrinorsum d'Orb. 

 Inoceramus plicatus d'Orb. 



C 20. TRINIDAD. 



Wall and Sawkins ^'^^^ described the Older Parian group of the Island of Trinidad 

 as Lower Cretaceous. 



The Older Parian group consists of a great variety of sandstones, fine or coarse grained and 

 usually highly indurated, which properly seems referable to the extensive diffusion of siliceous 

 cementing material; of shales of a dark color, characterized by flakes of silvery white mica; 

 and of strata composed of an argillaceous base, with small equivalents of carbonate of lime and 

 free silica. * * * 



Limestones are rare, do not exceed 10 to 20 feet in thickness, are extremely compact, and 

 their fossils usually partially or entirely transformed into highly crystalline spar. * * * 



Very few fossils were collected in this formation, and those obtained were from a single 

 limestone at Point a Pierre, but none of them offering any characters sufficiently precise for 

 defining the geological position. Some fossil remains procured from the same series at Cumana, 

 in Venezuela, fortunately present a more positive aspect and are referable to the later secondary 

 period. It is highly probable that these strata are of similar age to the upper secondary deposits 

 of New Grenada, which are attributed by Von Buch and D'Orbigny to the Neocomian or Lower 

 Cretaceous horizon. 



Disturbances are everywhere characteristic, the angle of dip is almost invariably high, and 

 the strata are often vertical; but buried as the formation usually is in the center of the densest 

 forests, it is extremely difficult to obtain sections adapted for resolving the details of position. 

 These disturbances are by no means referable to a single series, since the consolidation, perhaps 

 rapid, and the first elevation must have transpired before the newer Parian deposits were 

 formed, and consequently anterior to the Miocene epoch. Ulterior movements, possibly 

 repeated at intervals, affected both groups nearly equally, since in Naparima and the southern 

 districts the Tertiary members are found at high angles reposing apparently conformably on 

 the subjacent Older Parian. 



E. H. Cunningham-Craig,^"" Government geologist of Trinidad, made fourteen 

 brief reports to the legislative council between 1904 and 1907 inclusive and 

 described local details, especially of the oil fields in Tertiary strata. 



