Venezuela

by Leonard V. Dalton

Here and there throughout the mountains of northern Venezuela, the traveller is sure to be struck by the sight of great cliffs and castle-like masses of limestone rock, which add greatly to the effect of the scenery where they occur. From their position it is clear that these were originally parts of a more or less continuous accumulation of lime in a deep, still sea, after more turbulent waters had deposited the Segovia Group. The German traveller Dr. Sievers called this limestone the Capacho Limestone, from Capacho in Táchira. The fossils are similar to those of the period of the higher parts of the chalk.

After the deposition of the Capacho Limestone the earth’s crust, which had in this region remained tranquil for a considerable period, again underwent some changes, and in the new shallower sea thus formed sand and mud, with some lime, were alternately laid down. The resulting sandstones, shales, and limestones were named by Dr. Sievers the Cerro de Oro Series, from a hill formed of these rocks in Táchira, and called Cerro de Oro, or Golden Hill, because the very abundant iron pyrites in it were mistaken for the precious metal. Many fossils have been found in the group, and from these it seems that in Venezuela, instead of the break between Cretaceous and Tertiary which we have in England, there was a continuous series of deposits, so that at the base we have chalk fossils, and higher up Eocene forms, the general character of the animal life changing gradually from one to the other.

With the consolidation of the Cerro de Oro beds we have a new period of disturbance, in which the mountain chains of northern Venezuela began to be formed as we know them to-day, and the waters of the Orinoco began to flow into the Atlantic more or less by the present mouth of the river. Alongside the newly formed hills, or islands as they would then be, sandstones and shales were deposited to a considerable thickness. They are found outcropping now along the coast and under the Llanos, as well as round the Lake of Maracaibo. The first fossils from them were collected by Mr. G. P. Wall from Cumaná, and it seems fitting to distinguish the whole as the Cumaná Series.

After the deposition of the Cumaná Series, and the crust movements which led to the consolidation and folding of these rocks, the physical features of Venezuela must have been very much what they are to-day, save that many of the smaller islands and parts of the coast were still submerged as shoals, whilst the Llanos seem to have been a great swampy or submerged plain, with deep water in parts, over which the Orinoco sediments gradually accumulated in the form of current-bedded sands and clays surmounted by gravels, which we may term the Llano deposits. At the same time, along the coast and on the shoals shell-beds were being formed, and can now be seen at Cabo Blanco, west of La Guaira, and similar places, while practically the whole surface of the Island of Cubagua is formed of them, suggesting the name Cubagua Beds. About this period some volcanic rocks were thrust up and cooled both in the Peninsula of Paraguana and near San Casimiro, south of Carácas. In the mountains great masses of gravels containing huge boulders and some Megatherium and other bones were being piled up by the rivers. Last of all we have the still-accumulating recent alluvium of the modern streams, attaining its widest extent in the Delta and round the Lake of Maracaibo.

No volcanoes, active or recently extinct, are known in Venezuela, but the country has, like most of South America, been continually subject to earthquake shocks of greater or less intensity. Some of these are historic, but of the many others recorded not a few had far-reaching effects on the population. The first important tremor noticed after the discovery and settlement of the shores of the Caribbean was that of 1530, which shook the city of Nueva Cadiz on the Island of Cubagua and destroyed the fortress of Cumaná, thus checking for some time the colonisation of the mainland in this region. Thirteen years later New Cadiz was visited again by earthquake and hurricane, and so disastrous were the results that from that day to the present Cubagua has been, what it was before the arrival of the Spaniards, a desert island. The many shocks experienced in the course of the seventeenth and eighteenth centuries seem to have been generally unaccompanied by much loss of life or property, but this period of comparative quiescence was followed by one of the historical examples of severe earthquake early in the nineteenth century. In March, 1812, a shock destroyed great parts of Carácas, La Guaira, Barquisimeto, Mérida, and other towns, and in the capital alone ten thousand people were killed. The great earthquake which, on August 13, 1868, made itself felt all over South America, so much affected some of the Venezuelan rivers that their waters over-flowed the banks, and even remained for a short time in new channels. In 1894 Mérida and other towns in the Andes suffered much damage, houses and churches being shaken down; the destruction was in some cases extraordinarily complete. Since that time only slight tremors have been felt.

The internal heat in the north-eastern spur of the Andes, which traverses Venezuela, manifests itself at many points in the form of hot springs. One, containing much sulphur, is found at Las Trincheras, between Valencia and Puerto Cabello. The temperature of this spring varies, but in 1852 it was found by Karsten to be only a few degrees below the boiling point of water; in general, however, it does not exceed 195° F. or 17° below boiling point. Wall found one south of Carúpano actually boiling. All along the flanks of the coastal Cordillera there are mineral springs, generally at fairly high temperatures, and many more are known throughout the Andes. Nearly all these springs have been used in the treatment of various diseases, though none has achieved especial popularity.

While hot springs may be interesting to the visitor, they are hardly valuable assets to a country such as Venezuela, but this part of the world has always, and with much justice, held the reputation of being rich in minerals. There is coal of fairly good quality in more than one of the Cretaceous and Tertiary groups of strata, near Barcelona, Tocuyo, Coro, and Maracaibo, as well as in the Andes, but the often-associated iron is only found in large quantities in the Guayana gneiss south of the Orinoco Delta.

Gold, that great lure for the early European ventures to the west, may be said to occur in almost every State of Venezuela, but it has only been worked with profit in Guayana, even though samples of a quartz-reef near Carúpano are said to have assayed 7 oz. to the ton. When Sir Robert Dudley visited the coast of the Gulf of Paria in 1595, he heard of a goldmine near Orocoa (Uracoa), on the eastern side of the Llanos, which may mean that the gravels are occasionally auriferous, but unfortunately he failed to reach the place. Placer workings are the chief source of the precious metal in the Guasipati goldfields in Guayana, but the reefs from which it is derived have been discovered and worked at odd times. In British Guiana, where the conditions are similar, Mr. Harrison says that the gold is generally found along the later intrusive dykes, the smallest dykes being the richest, while most gold is found where a basalt intrusion crosses one of the older ones.

The ores of copper are fairly common in the northern Cordillera, and the mines of Aroa in Yaracuy have been worked for many years. Here the pyrites veins occur in the Capacho Limestone, not far from where it has been invaded by a mass of granite. In the Andes it seems to occur in the more ancient rocks, as near Seboruco in Táchira, and Bailadores in Mérida. A mine near Pao seems to be in Cretaceous rocks.