On the Geology of part of Venezuela and of Trinidad. 165 



is occasionally auriferous. Very small proportions of copper-ores 

 and argentiferous galena exist in some localities 



The Serrania also comprises another great group of strata, flanking 

 the " Caribbian " rocks on the south, and in the eastern district 

 rising to a height of more than 7000 feet, with a breadth of from 

 30 to 40 miles. These consist of sandstones, fossiliferous limestones, 

 and shales ; and form the group provisionally termed " Older 

 Parian " by the author, from the circumstance of its occurring on 

 the shores of the Gulf of Paria. In Trinidad it is traced as a narrow 

 belt across the island. 



Alternating with the sandstones and limestones are thick beds of 

 a rock containing 85 per cent, of clay and only about 3 per cent, of 

 carbonate of lime. This is provisionally termed " ArgiHine." An- 

 other peculiar bedded rock of this series is composed of nearly pure 

 and very fine siliceous matter : it is noticed by the author under the 

 name of " Chertine." 



These Older Parian strata must be nearly 8000 feet thick. They 

 have been intensely disturbed. Though the fossils can rarely be 

 separated from the matrix, yet some were fortunately obtained from 

 near Cumana, — namely, Trigonice and small Gasteropoda. Mr. 

 Etheridge, F.G.S., suggests that most probably they indicate a 

 Lower Cretaceous age. These Lower Parian rocks extend west- 

 ward into New Granada ; and are probably related to the Neocomian 

 rocks of Bogota. 



Near their junction with the "Caribbian Group," the Older 

 Parian strata are often interstratified and alternate with rocks of 

 igneous origin. The base of these pyrogenic rocks varies from 

 augitic to diabasic in their type. 



The Llanos or grassy plains of Venezuela are entirely formed of 

 conglomerates and sandstones referable to the next great group of 

 strata, namely the M Newer Parian." In Trinidad a lower and 

 calcareous portion of this group exists. Altogether this group pro- 

 bably has a thickness of nearly 4000 feet. In the plains of the 

 mainland the strata are horizontal ; but in Trinidad they have suf- 

 fered great disturbance. 



Fossils are abundant in the calcareous divisicn, and seem to repre- 

 sent the Lower Pliocene or Upper Miocene series of Europe. 



The materials of the conglomerates and sandstones have been 

 mainly derived from the disintegration of the Lower Parian rocks. 



The upper portion of the Newer Parian series, which is often 

 shaly, contains beds of lignite, frequently admitting of exploitation. 

 The lignite occurs at several localities on the mainland, and also in 

 Southern Trinidad. The lignitiferous beds have locally undergone 

 combustion to a great extent, from natural causes, such as the de- 

 composition of pyrites. The result is that the strata have been in- 

 durated and baked for a vertical extent sometimes of 70 or 80 feet ; 

 the clays assuming various conditions, and presenting the " porcel- 

 lanites " and " thermantides " of continental authors. 



The asphalt of Trinidad and the mainland is almost invariably 

 disseminated in the upper part of the Newer Parian group. When 

 in situ, it is confined to particular strata, which were originally shales 



