I Cannot Decide Whether Araya, Which Is Rich In Disseminated Muriate Of Soda, Belongs To The Sandstone Formation Of The Imposible, Which From Its Position May Be Compared To Variegated Sandstone (Red Marl).

There is no doubt that fragments of tertiary strata surround the castle and town of Cumana (Castillo de San Antonio)

And they also appear at the south-western extremity of the peninsula of Araya (Cerro de la Vela et del Barigon); at the ridge of the Cerro de Meapire, near Cariaco; at Cabo Blanco, on the west of La Guayra, and on the shore of Porto Cabello; they are consequently found at the foot of the two slopes of the northern chain of the Cordillera of Venezuela. This tertiary stratum is composed of alternate beds of calcareous conglomerate, compact limestone, marl, and clay, containing selenite and lamellar gypsum. The whole system (of very recent beds) appears to me to constitute but one formation, which is found at the Cerro de la Popa, near Carthagena, and in the islands of Guadaloupe and Martinico.

Such is the geological distribution of strata in the mountainous part of Venezuela, in the group of the Parime and in the littoral Cordillera. We have now to characterize the formations of the Llanos (or of the basin of the Lower Orinoco and the Apure); but it is not easy to determine the order of their superposition, because in this region ravines or beds of torrents and deep wells dug by the hands of man are entirely wanting. The formations of the Llanos are, first, a sandstone or conglomerate, with rounded fragments of quartz, Lydian stone, and kieselschiefer, united by a ferruginous clayey cement, extremely tenacious, olive-brown, sometimes of a vivid red; second, a compact limestone (between Tisnao and Calabozo) which, by its smooth fracture and lithographic aspect, approaches the Jura limestone: third, alternate strata of marl and lamellar gypsum (Mesa de San Diego, Ortiz, Cachipo). These three formations appeared to me to succeed each other in the order I have just described, the sandstone inclining in a concave position, northward, on the transition-slates of Malpasso, and southward, on the gneiss-granite of Parime. As the gypsum often immediately covers the sandstone of Calabozo, which appeared to me, on the spot, to be identical with our red sandstone, I am uncertain of the age of its formation. The secondary rocks of the Llanos of Cumana, Barcelona and Caracas occupy a space of more than 5000 square leagues. Their continuity is the more remarkable, as they appear to have no existence, at least on the east of the meridian of Porto Cabello (70 degrees 37 minutes) in the whole basin of the Amazon not covered by granitic sands. The causes which have favoured the accumulation of calcareous matter in the eastern region of the coast chain, in the Llanos of Venezuela (from 10 1/2 to 8 degrees north), cannot have operated nearer the equator, in the group of the mountains of the Parime and in the plains of the Rio Negro and the Amazon (latitude 1 degree north to 1 degree south). The latter plains, however, furnish some ledges of fragmentary rocks on the south-west of San Fernando de Atabapo, as well as on the south-east, in the lower part of the Rio Negro and the Rio Branco.

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