GEOLOGICAL HISTORY OF VENEZUELA: ERAS AND FORMATIONS - GEOGRAPHY - 2024

The geological history of Venezuela began 4.6 billion years ago, when the first igneous and metamorphic rocks were formed that gave rise to the Guayana region.

The geologists agreed to identify large groups that allowed an idea of ​​the evolution of the geographical forms of Venezuela. Thus four eras were determined: Precambrian, Paleozoic, Mesozoic and Cenozoic. These, in turn, were fragmented in different periods.

The geological history of Venezuela includes the evolution of the Guiana shield and the final part of the great Andean mountain system, made up of the Andes Mountains and the Costa Cordillera. These were the main geographical accidents from which other minor ones were generated.

In the first place, the Guiana massif was formed, in the south of the country, where important mountain ranges emerged. Later, in the north, the Andes mountain system emerged.

In the valley that currently unites them, there was only water; thus, for a time the Venezuelan territory was reduced to two islands.

With the growth and transformation of the mountains, various sediments reached the lake that separated the two islands, to fill it and generate the great valley known as the Venezuelan plains.

The geological eras in Venezuela

In the geological history of Venezuela, as in that of the world, four eras are identified that account for the formation and transformation of its relief: Precambrian, Paleozoic, Mesozoic and Cenozoic.

Precambrian era

The Precambrian era began 4.6 billion years ago and is counted until 570 million years ago.

During this period the basal complex of Venezuelan Guiana was created, in the south of the country; also in the Andes; in the northern mountain range of Perijá, state of Zulia; and in the trunk, state of Cojedes.

Paleozoic era

This era lasted 325 years and is counted from 570 to 245 million years ago in the history of geology.

During this era the primitive Andes arose, to the northwest of the country; initially there was a kind of elevation of the mountains and, later, a wear. Currently there are reliefs that still belong to this era.

The tectonic plate, called South American, moved slightly to the west. And the plate known as del Caribe moved eastward, raising the territory in the form of mountain ranges.

Mesozoic era

During the Mesozoic era the Cordillera de la Costa was formed, and it developed from 245 to 65 million years ago.

In this era, from the Caribbean Sea emerged what is now known as the mountainous system, which surrounds the northwest coast of Venezuela.

Cenozoic era

The Cenozoic era has developed from 65 million years ago to the present day.

It was in this period when the Andes that we know today were finished forming and, after the sedimentation that this formation left in its wake, oil deposits were deposited in the state of Zulia and towards the east.

In addition, the Orinoco River delta was expanded, and the Lake Maracaibo basin sank giving way to new mountains.

The main Venezuelan geological formations

1- Guiana Shield

The Guiana Shield is one of the oldest geological zones on the planet and occupies Venezuelan, Colombian and Brazilian territory; it is estimated to be 3,500 years old.

The transposition of two tectonic layers - the South American and the Caribbean - raised the territory that was under the sea and created a set of mountain ranges and mountains, which make up the Guayana region in Venezuela.

The oldest rocks in Venezuela are found at this site and it is known as the “Basal Complex”. It is formed mainly by igneous rocks, among which is granite.

1,500 million years ago a sedimentary cover was deposited in the region of Guayana, formed by sandstone for the most part, giving rise to the plateaus known as tepuis.

The same process of erosion created a large deposit of sand on the banks of the Orinoco River, generating the largest area of ​​dunes in the country, in the state of Apure.

Currently this area is known as the Santos Luzardo National Park and there the sand dunes or sand dunes coexist with mighty rivers and savanna vegetation.

Among the main formations of the Guiana shield are El Callao, located near the Yuruari River and with volcanic formations.

It is also possible to find the formation on the Cicapra creek, formed by stones known as amphibolics, interspersed by volcanic cracks.

There are also the Yuruari, Caballape, Cuchivero and Roraima formations.

2- Cordillera de Los Andes

After the Táchira depression, and after the continuation of the Andes mountain range towards the northeast, there is the Mérida mountain range, which extends to the Barquisimeto and Carora depression.

The western chain of the mountain system is made up of the Sierra de Perijá, which rises to 3,750 meters, and the eastern chain that forms the Mérida mountain range and culminates in Pico Bolívar, at 4,978 meters.

The two mountain ranges enclose the depression of Lake Maracaibo, with 13,280 km².

Among the most outstanding formations are that of Bella Vista; Caparo, with some fossiliferous slates; and the Mucuchachí formation, made up mainly of gray to brown shales, sometimes carbonaceous, silty and containing fossils and pyrites.

The Sabaneta formation also stands out, consisting mainly of yellow, gray, red-violet and brown sandstones. There are also the Palmarito formation, in the south of the state of Mérida, and the La Quinta formation.

3- The plains

The Venezuelan plains occupy 35% of the national territory and were formed thanks to the sedimentation suffered by a large lake that separated the Guayana region and the Andes and Costa mountain ranges.

This region also includes the plain of the Orinoco river delta, whose characteristics are very similar to those of the llanos region.

References

1. Gomey David et al. (2007) Chronology of Cenozoic tectonic events in western Venezuela and the Leeward Antilles based on integration of offshore seismic reflection data and on-land geology. The American Association of Petroleum Geologists V. 91. pp: 653-684.
2. Mencher E. et al. (1953) Geology of Venezuela and Its Oil Fields. Bulletin of the American Association Petroleum Geologists. V. 37 No. 4. pp: 690-777
3. McNab JG et al. (1952). Evolution of Petroleum. Industrial and Engineering Chemistry. 44 (11), pp: 2556–2563
4. Macqueen, RW, & Leckie, DA (1992). Foreland basins and fold belts. United States: Tulsa, OK (United States); American Association of Petroleum Geologists.
5. Prieto, R., & Valdes, G. (1990). The Furrial oil field, a new giant in an old basin. In AAPG Bulletin (American Association of Petroleum Geologists); (USA) (Vol. 74: 9). United States.