Talk:Falcon Basin

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Introduction

The Maracaibo-Falcon basin extends east-northeast across the States of Zulia and Falcon with a length of approximately 525 kilometers and a maximum width of 300 kilometers. The Maracaibo basin, nowadays represented by an extensive bay of shallow salty waters surrounded by lowlands, constitutes a deep structural depression between the frontier region of the Guajira to the north (today partly submerged), the Sierra de Merida to the south, the mountainous regions of Falcon and Trujillo on the east and the Sierra de Perija and Cordillera Oriental de Colombia to the west [1]. The Falcon basin situated north of the Serrania de Trujillo and northwest of the Cordillera de la Costa, and immediately east of the Maracaibo Basin, represents a province of Tertiary rocks raised in long rows caused by intense folding during orogenic movements of the Tertiary. Nowadays the region is exposed to erosion with the consequent deposition of alluvial cones and terraces in the plains and foothills of the mountains, and of coastal deposits in lagoons along the coastal zones.

History

The most active geologic investigation of the Falcón Basin took place between 1912 and 1980 and related to petroleum exploration of the region. During this period, 200 exploratory wells were drilled and more than 12,000 km of seismic lines were acquired. Early geological exploration focused on the coastal plain of northwestern Venezuela and proximal offshore areas, whereas the interior of Falcón State remains poorly studied. The compilation works by Gonzálezde Juana, Macellari, Muessig, Porras, Senn and Zambrano, Vásquez, Duval, Latreille, and Coffinieres integrated the geological knowledge that resulted from this exploration period. Another critical contribution concerning the stratigraphy of the Falcón Basin is that published by Wheeler, which was built on the exploration campaigns carried out by geologists from Creole Petroleum Corporation over 10 years. These reports include the first geological cartography of Falcón State in a series of 1:100,000 and 1:50,000 scale unpublished maps [2]. All subsequent geological mapping of this region has been based upon the Creole Petroleum Corporation geological cartography. The biostratigraphic framework of the Falcón Basin was produced by Díaz de Gamero, based on planktonic foraminifera.

Stratigraphy

In order to discuss the tectonics and stratigraphy of the Maracaibo-Falcon basin we ought to consider the present regional relationships between this basin and the adjoining Barinas-Apure and Magdalena basins since they originally formed part of the large northern Andean geosyncline that extended from Venezuela to Peru. This geosyncline began to form at the beginning of the Mesozoic because of a differential sinking of a broad zone limited on the southeast by the Guayano-Brasilero shield which constituted a positive element during the Mesozoic and Tertiary [3]. The depositional cycle began with an accumulation of a series of coarse Triassic-Jurassic sediments of continental origin. At the end of the Jurassic, orogenic disturbances occurred which were followed by a long period of erosion before the beginning of the transgression of the seas in the Cretaceous. During the Cretaceous, sedimentation was extensive across the geosyncline. In the western part of the country, this deposition continued during a good part of the Eocene although the sea was less deep and more limited due to a gentle and widespread uplift occurring at the end of the Mesozoic which raised the basin slowly from the southwest causing the withdrawal of the sea toward the northeast and continual lithological changes in the character of the sediments. Toward the final stages of the Eocene and because of a pronounced orogenic disturbance, the northern Andean geosyncline began to divide into various sedimentary basins that were interconnected in certain epochs of the upper Tertiary, thus leaving it in existence as a tectonic unit of importance.

Depositional History

PALEOZOIC Prior to the development of the northern Andean geosyncline and along the zone that this occupied later, although a little more to the south and east, a Paleozoic geosyncline existed on the present borders of the Guayana shield. Its sediments were severely affected by the Hercynian orogeny during the Lower Carboniferous; nevertheless, these effects, obscured by metamorphism and later orogenic movements, are nowadays difficult to recognize and interpret. The effects of the Appalachian orogeny of the Permian are easier to recognize although its details still remain obscure. After the Appalachian orogeny and during the Mesozoic deposition in the northern Andean geosyncline, the region occupied by the Paleozoic sediments adjacent to the Guayana shield became a stable part of the region.

The Pre-Cambrian rocks upon which the Paleozoic rocks were deposited, outcrop in the Sierra de Merida and in the region of El Baul. These rocks are comprised principally of gneisses, schists, other metamorphic rocks, and granites. In El Baul Paleozoic clays with trilobites, and in the Sierre de Merida slates and schists of the Mucuchachi (Cambrian-Devonian) outcrop. The beds of Rio Momboy with Devonian fossils are considered equivalent to part of the Mucuchachi Formation. In the Sierra de Perija sandstone, shales, limestones, and unmetamorphosed quartzites of the Rio Cachiri (Devonian) Formation are observed. In the Sierras de Merida and Perija soft shales and massive crinoidal limestones of the Palmarito (Permo-Carboniferous), Formation is found [4].

MESOZOIC At the beginning of the Mesozoic, after the Appalachian revolution and the deformation of the Paleozoic rocks, extensive continental deposits were laid down in continental basins. These deposits are characterized by alluvial sediments of intense red color, principally massive banks of conglomerates interbedded with fine-grained sandstones and limonites which make up the La Quinta Formation. Afterward, the La Quinta Formation was intruded by sills and dikes, probably during new uplift movements at the end of the Jurassic.

The geological history that has the greatest importance from the petroleum standpoint began with the sinking of the northern Andean geosyncline and the deposition of the Cretaceous formations. At the beginning of the Cretaceous, the erosional materials of the Guayana shield and the zone of Paleozoic rocks (and possibly of positive elements resulting from the uplift movements in the Jurassic) were deposited in the form of a thick series of feldspathic sandstones and quartz conglomerates of some 1000 meters in thickness although locally it reaches up to 3000 meters. These sediments, designated the Rio Negro Formation, are only found in the northwestern part of Venezuela and probably represent the first cycle of the progressive sinking of the geosyncline.

TERTIARY During the Paleocene (Figure 4) the series of environments already described moved toward the north somewhat more with the consequent deposition of the terrestrial clays of the Lisama Formation of Colombia near the uplift of the Cordillera Oriental and Sierra de Santa Marta, of the sandstones and coals of the Orocue Group and Angostura Formation, of salt water shales, probably in a small bay environment, of the Marcelina Formation and, finally, of the Guasare Formation deposited in the central part of the Maracaibo basin under a shallow water reef environment [5]. Toward the open sea, there was a deposition of clays and fine-grained sandstones of the Trujillo Formation in a small bay environment, of sandstones and shallow water shales of the Rancheria Formation, and of shales and deep water limestones of the Valle Hondo Formation.

At the end of the Paleocene and at the beginning of the Eocene the Sierra de Perija was elevated, as was also the Sierra de Santa Marta and part of the Cordillera Oriental of Colombia, which caused the beginning of a series of variable environments that continued through the remainder of the Tertiary. This series was characterized by conditions that varied from salty waters and lagoons in the west along the Sierra de Perija to open sea conditions in the east across Falcon. On the paleogeographic map of the Lower Eocene (Figure 5) the newly emerged Sierra de Perija and the zones of terrestrial deposition are indicated which are expressed by the sandstones and conglomerates of the Angostura Formation (Colombia) and the upper part of the Oracle Formation and possibly by the river sandstones of the Mirador Formation. Toward the east, the terrestrial deposits pass gradually and laterally to sandstones, clays, and coal of the swampy environment of the Paso Diablo and Angostura Formations and further east to lagoon deposits of interbedded sandstones and shales of the Misoa-Trujillo Group. The deposition of the shallow water sandstones and shales of the Rancheria Formation and of the deep water shales and limestones of the Valle Hondo Formation apparently was not affected by the uplift. These conditions ended in the Middle Eocene [6].

Further Reading

-https://www.foxbusiness.com/politics/chevron-oil-drilling-venezuela-blasted-stupidity-nonsensical -https://www.opec.org/opec_web/en/about_us/171.htm

References

-Baquero, M., Acosta, J., Kassabji, E., Zamora, J., Sousa, J. C., Rodríguez, J., . . . Schneider, F. (2009). Polyphase development of the Falcón Basin in

northwestern Venezuela: Implications for oil generation. Geological Society, London, Special Publications, 328(1), 587-612. doi:10.1144/sp328.24

-Albert-Villanueva, E., González, L., Bover-Arnal, T., Ferràndez-Cañadell, C., Esteban, M., Fernández-Carmona, J., . . . Salas, R. (2017). Geology of the

Falcón Basin (NW venezuela). Journal of Maps, 13(2), 491-501. doi:10.1080/17445647.2017.1333969

-Tito, B., & Donald, G. (1991). Chapter 11 a new geologic model related to the distribution of hydrocarbon source rocks in the Falcon Basin,

northwestern Venezuela. Active Margin Basins. doi:10.1306/m52531c11

-McMillen, R. (1963, January 01). The Maracaibo-Falcon Basin-Venezuela: Semantic scholar. Retrieved December 7, 2022, from

https://www.semanticscholar.org/paper/The-Maracaibo-Falcon-Basin%E2%80%94Venezuela-McMillen/d858e3fa011503ffc0757f79fa2fed5cf5018287

-Molina, A. (1993, January 01). Tiguaje Field--venezuela maracaibo/falcon basin, Falcon State. Retrieved December 7, 2022, from

https://archives.datapages.com/data/specpubs/fieldst3/data/a022/a022/0001/0250/0295.htm