Geology of the Colombian Amazon
DOI:
https://doi.org/10.32685/0120-1425/bolgeol22.3.1979.279Keywords:
Colombia, Amazonas, geological cartography, geomorphology, denudative origin, terraces systems
License
Copyright (c) 1979 Servicio Geológico Colombiano
This work is licensed under a Creative Commons Attribution 4.0 International License.
Downloads
How to Cite
Issue
Section
Published
Abstract
The regional geological mapping in this work corresponds to an area of 380 000 km2 in the Colombian Amazon, located in the southeastern part of the Republic of Colombia, bordering Venezuela, Brazil, and Peru.
The geology described here is part of the multidisciplinary research program that since 1974 has been carried out by the Radargram metric Project of the Amazon, "Proradam," in the southeast of the country, whose objective is to evaluate its natural resources. In the geological aspect, the systematic interpretation of radar images is carried out, with field verifications to establish the different lithological units in the area.
A geomorphological sketch of the region was made based on radar interpretation, dividing the area into four major geomorphological units: Provinces of landscapes of structural origin, denudational origin, terrace systems, and alluvial landscapes.
Chronologically, the following geological units are recognized, starting from the oldest ones: Migmatitic Complex of Mitú, La Pedrera Formation, Roraima Formation, Granófiro del Tijereto, Piraparaná Formation, Diabatic Dikes, Araracuara Formation, Nepheline Sienite of San José del Guaviare, Amazonian Lower Tertiary, Amazonian Upper Tertiary, and Quaternary Deposits. These units, except for the Roraima Formation and the Nepheline Sienite of San José del Guaviare, are proposed in this work as new stratigraphic units.
The Mitú Migmatitic Complex includes sandy and pelitic metasedimentary, basic, and quartz-feldspathic metaigneous, blastomilonites and migmatitic granites, the latter with a composition ranging from alaskite to monzonite. The age of the complex is Precambrian and is part of the Guayana Shield.
The La Pedrera Formation consists of a sequence of sandy - pelitic Precambrian sediments, folded and subjected to incipient metamorphism. The sandy facies is widely predominant over the pelitic facies, and there is always intercalation between the two. The Roraima Formation is integrated by a thick Precambrian folded sequence. A lower segment is formed by conglomerates, conglomeratic sandstones, quartzites, sandstones, and shales and an upper segment is formed by a second conglomerate and a thick orthoquartzite column. Finally, the Granófiro del Tijereto presents a variable composition in a series of isolated outcrops from the Vaupés River to the Caquetá River, west of the Piraparaná Formation.
The Piraparaná Formation consists of a sedimentary volcano sequence composed of pyroclastics, red sediments, and rhyodacite lavas of the Precambrian age, present in a wide arc from the Vaupés River to Caquetá. Diabasic dikes occur intruding rocks of the Mitú Migmatitic Complex and the Pedrera Formation; some of the dikes found in the Piraparaná River are of basic alkaline character.
The Araracuara Formation is composed of a basal conglomerate and a sequence of sandstones, glauconitic sandstones, and, to a lesser extent, claystones. It presents some fossils that have allowed it to be dated as Paleozoic. It outcrops in a wide area in the central part of the Colombian Amazon.
The San José del Guaviare Nepheline Syenite, of Paleozoic age, outcrops in a small sector west of the mentioned town and probably in the region of Cerro Cumare in the Intendencia del Caquetá.
The Lower Tertiary Amazonian sediments consist of blue clays with lamellibranchs observed in the southern part of the area.
The sequence designated in this report as Amazonian Upper Tertiary presents at its base a conglomerate with ferruginous cement and abundant marcasite concretions, locally accumulations of oolitic iron and siderite; on top of it appear reddish clays with lignites and poorly consolidated sandstones.
The Quaternary Deposits are made up of sands of possible eolian origin, terraces, and recent alluvium.
The fracturing of the Shield has two main directions varying from NNE to NW. Precambrian sedimentary structures are folded and fractured, with a general NNW - NW orientation. The rest of the structures are characterized by their horizontal disposition.
Regarding Economic Geology, it is necessary to note the absence of the two most important types of deposits in the Precambrian era worldwide, the taconites and the massive sulfides associated with basic rock belts. Thus, the interest presented by the Colombian part of the Guiana Shield is directed more towards radioactive in elastic sediments and recent sedimentary iron.
References
AGUERREVERE, S. E., LOPEZ, V. W. y FREEMAN, C. A., 1939.- Exploración de la Gran Sabana. Rev. de Fomento. Año 3, No. 19, p. 501-729, Caracas.
BARRBOSA, O., 1967.- Tectonica na bacía Amazónica. Atas Simp. Biota Amazónica, Geoci., Rio de Janeiro, 1: 83 - 86.
BARROSA, O. y RAMOS, J. R. A., 1959.Territorio de Rio Branca, aspectos principais da geomorfologia da geologiae das possibilidades minerais da sua zona setentrional. Bol. Div. Geol. Mineral, 196, 49 p. Río de Janeiro.
BELLIZZIA, C. M., 1972.-Paleotectónica del Escudo de Guayana. In: Conferencia Geológicu Inter Guayanas, 9a., 1972. Memoria – Guayana Ministerio de Minas e Hidrocarburos (Bol.Geol. Pub., Esp. 6), p. 251 - 305.
CHOUBERT, B., 1957.- Essai sur la morphologie de la Guyane. Mémoire pour servir a l'expedition de la carte geologique détailléc de la France. Impr. Nationale, 48 p. París.
DAVIS, W. M., 188 9.- Geomorphology Batsford, London. 140 p.
DOMINGUEZ, C.A., 1976.- Clima amazónico y su influencia sobre el régimen hidrográfico y la utilización de suelos. Reunión suelos amazónicos. IPGH/IGAC. Instituto Colombiano de Antropología, Bogotá, Colombia.
FREILE, J. A., 1968.- Regiones climáticas de Venezuela. Ministerio de Minas e Hidrocarburos. Bol. Geol. Vol.X. No. 19, p. 3-156, Caracas.
GANSSER, A., 1954.- The Guiana Shield (South America), Edogae, Geol. Helvetia, V. 47, No. 1, p. 77 -112.
GEOTEC: LTDA. (COLOMBIA), 1976.- Mapa geológico de Colombia.
HARGRAVES, R.B., 1968.Paleomagnetism of the Roraima dolerites. Geophys. J., London, V. 16, p. 147 - 160.
HARRINGTON, H. J., 1962.- Paleogeographic development of South America. B. Amer. Assoc. Pe trol. Geol., Tulsa, v. 46, p. 1773 - 1814.
HUBACH, E., 1954.- Significado geológico de la Llanura Oriental de Colombia. Inst. Geol. Nal. Informe No. 1004. Bogotá.
INSTITUTO NACIONAL DE INVESTIGACIONES GEOLÓGICO-MINERAS (COLOMBIA), 1976.- Mapa Geológico de Colombia.
INSTITUTO NACIONAL DE INVESTIGACIONES GEOLÓGICO-MINERAS (COLOMBIA), 1978.- Mapa Gravimétrico de Colombia.
IRVING, E. M., 1971.- La evolución estructural de los Andes más septentrionales de Colombia. Ingeominas, Bol. Geol., v. XIX, No. 2, Bogotá.
KARSTEN, H., 1856.- Geognostische Verhaltnisse des Westlichen Colombien. Archivo, Ingeominas, Bogotá.
KARSTEN, H., 1886. - Equisse dune carte de la constitution geologiqu.e de la Colombie. Archivo, Ingeominas, Bogotá.
KEATS, W., 1976.- The Roraima formation in Guyana. A. Revised stratigraphy and proposed environment of deposition. in: II Cong. Latino Americano de Geología. Memoria – Ministerio de Minas e Hidrocarburos (Bol.Geol. Pub. Espec., 6) p. 901-936. Caracas.
KRUMBEIN, W. C., and SLOSS, L. L., 1963. - Stratigraphy and sedimentation, 2d ed: San Francisco, W. H. Freeman and Co., p. 93 -146.
McCONNELL, R. B., et al., 1964.- A new interpretation of the geology of British Guina. Nature, London, v. 204. p. 115 -118.
McDOUGALL, l., COMPSTON, W., HAWKES, D. D., 1963.- Leakage of radiogenic argvn and strontium from minerals in proterozoic dolerites from British Quina. Nature London, V. 198, p. 564 - 567.
MEDINA, E., 1978.- El futuro de la cuenca Amazónica, Rev. Interciencia v. 3, No. 4. Bogotá.
MEHNERT, K.R., 1971. Migmatites and the origen of granitic Rocks. Elsevier Publishing Co., Amsterdam, New York, 393p.
MONTALVAO, R.M. G., de, 1974.- Esboco geologico-tectonico do Gratan Guiones. In:Congresso Brasileiro de Geología, 28°, Porto Alegre. Sociedade Brasileira de Geologia, 1974. Boletin 1, p. 541 · 547.
OLIVEIRA, A. L., LEONARDOS, O. H., 1943. - Geología de Brasil. 2 ed. rev. atual. Ria de Janeiro, Seruico de informacao Agrícola, 813.p.
OPPENHEIM, V., 1942.· Rasgos geológicos de los Llanos de Colombia Orientales. Inst. Museo de la Univ. Na/. De La Plata, Tomo VII, No. 21, La Plata, Argentina.
PETTIJOHN, F. D., 1970.- Rocas sedimentarias: .2 da. ed. Buenos Aires, Ed. Universitaria, 731 p.
PJNSON, W.H., et al., 1962.· K/Ar and Rb/Sr ages of biotites from Colombia,
South America, Geol. Soc. America Bul/., V. 73, p. 907 - 910.
PRIEM, H.N.A., 1978. · First progress-report on the isotopic dating project in Columbia (Pruradam). Amsterdam.
PROJETO RADAMBRASIL, 1976.- Fo/ha NA. 19 Pico da Neblina, Levantamiento de Recursos Naturais, Ministerio das Minas e Energía V. 11, 373 p. Ria de Janeiro.
QUINTERO, R., 1976.- Notas geológicas sobre la región Vaupés, Caquetá. Informe inédito. Geocolombia. Bogotá.
REID, A. R., 1972.- Stratigraphy of the type area of the Roraima group, Venezuela, In: Conferencia Geológica Jn. ter-Guayanas, 9a., 1972. Memoria Guayana Ministerio de Minas e Hidrocarburos (Boletín de Geología, Pub/. Espec. 6), p.342 - 353.
SALATI, E., MARQUES, J., MOLJON, L., 1978.· Origem e distribuicao das chuvas na Amazonia, Reu. Interciencia, u.3, No.4. Bogotá.
SERVICIO GEOLÓGICO NACIONAL, 1944. Mapa Geológico de Colombia.
SERVICIO GEOLÓGICO NACIONAL, 1962. - Mapa Geológico de Colombia.
SNELLING, N. J., 1963.- Age of the Roraima Formation, British Guiana, Nature. London, v. 198, p.1079-1080.
SZCZERBAN, E., 1976.- Cavernas y simas en areniscas precámbricas de Territorio Federal Amazonas y Estado Bolívar in: JI Gong. Latinoamericano de Geología. Memoria . Ministerio de Minas e Hidrocarburos (Bol. Geol. Pub. Espec. 6) p. 1055- 1071. Caracas.
TAUSON, V.L., and KOSLOV, V.D., 1972. Distribution functions and ratios of frace-element concentrations as estimators of the ore -bearing potencial of granites. Geochemical Exploration, 1972, Lond. p.37-44.
TRICART, J. 1972. Landforms of the hum id tropics, foreata and sauannas. Longman Group Limited London, 306 p.
VAN DER HAMMEN, T., 1952.- Geología del Río Apaporis entre Soratama y Cachivera La Playa. Seru. Geol. Nal. Informe No. 834. Bogotá.
VESGA, J., CASTILLO, L., 1972.- Reconocimiento geológico y geoquímico preliminar del Río Guaviare, entre la confluencia con los Ríos Ariari e Iteviare, Informe No. 1631, Ingeominas, Bogotá.
WINKLER, H. G. F., 1967.- Petrogenesis of metamorphic rocks, 2d. ed New York, Springer-Verlag. 237 p.
