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Hoja Cachi.P65 Cachi 1 RESUMEN Pucará y Altos del Cajón de edad ordovícica repre- sentan el magmatismo paleozoico en la Cordillera La Hoja Geológica 2566-III, CACHI, está ubi- Oriental. cada en las provincias de Salta y Catamarca, en el Las sedimentitas cretácico-paleógenas del Gru- noroeste de Argentina. Esta cubre parte de dos pro- po Salta afloran en la Cordillera Oriental. Esta uni- vincias geológicas: la Puna en el oeste, la cual ocupa dad está integrada por los depósitos de sinrift del aproximadamente el 70% de la superficie de la Hoja, Subgrupo Pirgua, constituido por conglomerados y y la Cordillera Oriental o Subprovincia de las Cum- areniscas rojas, y las secuencias de postrift de los bres Calchaquíes, en el este. Subgrupos Balbuena y Santa Bárbara, integradas por Los pueblos de Payogasta, Cachi, Seclantas, Mo- areniscas, areniscas carbonáticas, pelitas y ocasio- linos y Angastaco constituyen las principales con- nales calizas correspondientes a las Formaciones centraciones urbanas en la parte oriental y las minas Lecho, Yacoraite, Mealla, Maíz Gordo y Lumbrera. Tincalayu y Fénix son los centros de desarrollo más El Paleógeno de la Puna está representado por importantes de la región puneña. Las principales ac- la Formación Geste, compuesta por conglomerados tividades económicas del sector oriental de la Hoja y areniscas, cuya fauna registra condiciones de cli- son la ganadería, agricultura y turismo, mientras que ma subtropical. La actividad del arco magmático en el sector occidental es la minería. andino y el acortamiento tectónico controlaron la Las provincias geológicas tienen una diferente naturaleza de las unidades neógenas en la Puna. Las expresión morfológica. La Cordillera Oriental está rocas volcánicas consisten en unidades subvolcánicas caracterizada por un paisaje de sierras y valles por (pórfidos de la Formación Inca Viejo) y lávicas donde discurren los ríos principales de la región. (dacitas y andesitas de la Formación Tebenquicho). La Puna corresponde a una altiplanicie con un ni- Los estratos depositados en cuencas orogénicas de vel de base de aproximadamente 4.000 m s.n.m., antepaís se subdividen en distintas unidades con serranías y cerros volcánicos que separan ex- formacionales, las cuales exhiben material provenien- tensas depresiones, muchas de ellas ocupadas por te del arco magmático terciario. Estas unidades son salares. La altura máxima corresponde al cerro la Formación Catal integrada por conglomerados y Galán (5.912 m). areniscas con intercalaciones ignimbríticas; la For- Las rocas más antiguas pertenecen a un basa- mación Batín constituida por conglomerados, are- mento metamórfico afectado por diferentes fases niscas y escasas tobas y la Formación Sijes integra- de deformación; este basamento está constituido por da por pelitas y areniscas con intercalaciones evapo- rocas sedimentarias y magmáticas neoproterozoicas ríticas y volcaniclásticas. (eocámbricas?), las cuales integran varias unidades: Los estratos neógenos de la Cordillera Oriental Formación Pachamama, Complejo Metamórfico Río integran el Grupo Payogastilla constituido por las Blanco y Metamorfita Antofallita en la Puna y For- Formaciones Quebrada de los Colorados, Angastaco, maciones Puncoviscana y La Paya en la Cordillera San Felipe y Palo Pintado. Estas unidades confor- Oriental. La Formación Cachi constituida por tron- man secuencias clásticas de conglomerados, arenis- dhjemitas, tonalitas y granitos de edad neopro- cas y escasas pelitas, con intercalaciones volcani- terozoica-eocámbrica intruye el basamento de la clásticas menores. La depositación de la Formación Cordillera Oriental. Angastaco es coetánea con la Ignimbrita Pucarilla, Las unidades fanerozoicas aflorantes en la Puna representando la manifestación distal del arco mag- y Cordillera Oriental son estratigráficamente dife- mático mioceno. rentes. Las sedimentitas marinas de la Formación El registro plioceno está limitado a la actividad Tolillar y las turbiditas de la Formación Falda Ciénega, volcánica de la Puna, representado por la Andesita ambas del Ordovícico, afloran en la Puna. En el Ratones y por el Complejo Volcánico Galán; a este Paleozoico inferior tiene lugar una intensa actividad último se asocia una de las mayores calderas de los magmática representada por las granodioritas y gra- Andes. La porción superior del Grupo Payogastilla nitos el Complejo Eruptivo Oire, aflorantes en el borde representa la sedimentación pliocena en la Cordille- oriental de la Puna y, localmente, en la Cordillera ra Oriental. Oriental. El granito de la Formación Cortaderas in- El Cuaternario comprende los depósitos de pie tegra parte de los plutones ordovícicos del borde de monte y conos de deyección vinculados genéti- occidental de la Puna, mientras que La Tonalita Las camente al relieve estructural impuesto por la com- Viñas de edad cámbrica? y los Granitos Angostura, presión plioceno-pleistocena. Asimismo, en la Puna 2 Hoja Geológica 2566-III tiene lugar el derrame de basaltos fisurales y de cen- tal controlan los procesos morfogenéticos resultan- tros monogénicos, representado por la Formación tes. La acción fluvial es más activa en la Cordillera Incahuasi, como así también el desarrollo de depósi- Oriental que en la Puna. tos evaporíticos que configuran extensos salares. En la región puneña se localizan los principa- La estructura de la comarca es el resultado de les recursos minerales de la Hoja. La actividad la superposición de varios procesos de deformación minera consiste en la explotación de depósitos ocurridos desde el Neoproterozoico. La actual con- evaporíticos, fósiles o actuales. La mina Tincalayu figuración del relieve data del Mioceno, período en explota boratos miocenos de la Formación Sijes y el cual se produce el engrosamiento cortical dife- la mina Fénix extrae litio a partir de salmueras del renciándose nítidamente la Puna de la Cordillera Salar el Hombre Muerto. La extracción de ulexita Oriental. Ambas regiones muestran fajas corridas y de los salares de Diablillos, Ratones y Hombre plegadas con fuertes anomalías geométricas, las Muerto constituyen explotaciones mineras meno- cuales se deben en gran parte a cambios en la cine- res. En la actualidad no se explotan minerales mática y velocidad de subducción del sistema de pla- metalíferos. La mina Incahuasi consistente en cas de Nazca y Sudamérica, y a la inversión de es- vetas de cuarzo aurífero, fue trabajada hasta me- tructuras previas. diados de siglo. El área de Diablillos es el pros- Las distintas características topográficas y pecto de mayor potencial descubierto al presente climáticas existentes en la Puna y Cordillera Orien- en la región. ABSTRACT Complex and Metamorfita Antafollita in the Puna region, and Puncoviscana and La Paya Formations Geological Sheet 2566-III, CACHI, occupies the in the Eastern Cordillera. The Neoproterozoic- provinces of Salta and Catamarca in northwestern Eocambrian Cachi Formation, which consists of Argentina. It encompasses two geological provinces: trondhjemites, tonalites and granites, intrudes the Puna, to the west, which covers about 70% of the Eastern Cordillera basement. mapped area, and the Eastern Cordillera or The Phanerozoic units exposed in the Puna and Subprovincia de los Valles Calchaquíes, to the east. Eastern Cordillera are stratigraphically different. The The Payogasta, Cachi, Seclantas, Molinos and Ordovician marine sedimentary rocks of the Tolillar Angastaco towns are the main population centers Formation and the turbidites of the Falda Ciénega in the eastern region whereas Tincalayu and Fénix Formation crop out in the Puna. An intense magmatic mines are the most important development areas in activity occurs in the lower Paleozoic. The granites the Puna. The main economic activities are cattle- and granodiorites of the Oire Eruptive Complex raising, agriculture and tourism in the eastern region intrude the eastern Puna basement and locally the and mining of non-metallic deposits is in the Puna Eastern Cordillera oldest rocks. The Ordovician region. granites of the Cortaderas Formation are part of the Geological provinces have different morpho- western Puna magmatic belt, whereas the logical expression. The Eastern Cordillera depicts a Cambrian? Las Viñas Tonalite and the Ordovician landscape of hills and valleys through which flow Angostura, Pucará and Altos del Cajón Granites are the main rivers of the region. The Puna is a plateau emplaced in the Eastern Cordillera basement. placed at about 4000 m above sea level with rising The Salta Group comprises Cretaceous- ranges, volcanic hills and large depressions, many of Paleogene sedimentary rocks, which are exposed in which are occupied by salt lakes. The highest peak the Eastern Cordillera. It includes the conglomerates in the Puna is Cerro Galán (5912 m). and red sandstones of the Pirgua Subgroup inter- The oldest rocks are part of a metamorphic preted to be syn-rift deposits, and the Balbuena and basement affected by several cycles of deformation; Santa Bárbara Subgroups considered to be post-rift this basement comprises Neoproterozoic (lower sequences. The latter include several units known Cambrian?) sedimentary and magmatic rocks named as Lecho, Yacoraite, Mealla, Maíz Gordo and Lum- Pachamama Formation, Río Blanco Metamorphic brera Formations, which are composed of sand- Cachi 3 stones, calcareous sandstones, pelites and scarce li- The Quaternary comprises piedmont deposits and mestones. alluvial-fan units, which are genetically linked with In the Puna region, the Paleogene stratigraphy the Pliocene-Pleistocene
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