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| Moquegua Group | |
|---|---|
| Name | Moquegua Group |
| Type | Stratigraphic group |
| Period | Oligocene–Miocene |
| Primary lithology | Andesite, dacite, tuff |
| Other lithology | Sandstone, conglomerate, limestone |
| Region | Moquegua Region, Arequipa Region |
| Country | Peru |
| Named for | Moquegua |
| Named by | (various geological surveys) |
| Thickness | up to several hundred meters |
Moquegua Group
The Moquegua Group is an Oligocene–Miocene volcanic and sedimentary stratigraphic ensemble exposed in southern Peru, notably in the Moquegua Region and Arequipa Region. It records interactions among Andean arc magmatism, forearc and backarc sedimentation, and basin inversion related to plate convergence between the Nazca Plate and the South American Plate. Important for regional correlations, the succession has been studied in relation to the Peruvian Andes, the Altiplano, and Miocene paleoenvironmental changes across western South America.
The Moquegua succession lies within the forearc to backarc transition of the central-southern segment of the Andes Mountain Range and is stratigraphically juxtaposed against older metamorphic and plutonic complexes such as the Mesozoic batholiths of Peru and the Puno Complex. Stratigraphic relationships include conformable to locally unconformable contacts with underlying Paleogene units and overlying Neogene volcaniclastic and alluvial deposits associated with the Maule Basin and other regional basins. Correlations have been drawn between Moquegua strata and coeval formations in the Tacna Basin, the Moquegua Basin, and sections documented near Arequipa, enabling integration with the regional chronostratigraphic framework established by national and international surveys.
Lithologically the group comprises volcanic flow units—principally andesite and dacite—interstratified with volcaniclastic tuffs, reworked tuffaceous sandstones, conglomerates, and localized limestones. Petrographic characteristics display porphyritic textures, plagioclase and hornblende phenocrysts, and glassy groundmasses consistent with arc magmatism recognized in the Central Volcanic Zone of the Andes. Depositional environments span proximal to distal volcanic slopes, alluvial fan systems linked to uplift along the Sub-Andean fold and thrust belt, fluvial channels comparable to modern paleoriver systems near Locumba River, and shallow lacustrine to marginal marine settings recorded in carbonate interbeds similar to lacustrine facies documented at Lake Titicaca-adjacent basins.
Biostratigraphic, magnetostratigraphic, and radiometric data constrain Moquegua Group deposition principally to the Oligocene through Miocene epochs. K–Ar and Ar–Ar dating of volcanic units returned ages that align with regional Miocene magmatic pulses recorded in the Peruvian Altiplano and the Central Volcanic Zone. Paleomagnetic studies tied to the geomagnetic polarity timescale permit correlation with marine and terrestrial records from the South Pacific and the Andean uplift history narrative. These age constraints situate the Moquegua Group within the timeframe of major tectonothermal events affecting the Coastal Cordillera and interior basins.
The Moquegua succession formed in a convergent margin setting controlled by the subduction of the Nazca Plate beneath the South American Plate, with magmatism driven by slab-related fluxing and crustal thickening during the Neogene. Volcanic centers linked to the group are part of the wider Central Volcanic Zone, sharing affinities with volcanic complexes such as Misti, Ubinas, and Sabancaya. Structural analyses reveal folding, thrusting, and strike-slip reactivation associated with the growth of the Andean orogeny and interactions with regional structures like the Cotahuasi fault system and the Pico de Chachani-related shear zones. Syntectonic sedimentation and volcanic loading influenced foreland basin geometries comparable to those of the Pisco Basin and other Peruvian sedimentary provinces.
Volcanic and hydrothermal processes recorded in Moquegua strata create settings favorable for epithermal and porphyry-style mineralization; sulfide-bearing veins, disseminated copper, gold, silver, and associated alteration halos occur in parts of the succession. Mineral prospects connected to Moquegua-age magmatism have been explored near mining districts adjacent to Quellaveco, Toquepala, and other resource-bearing districts in southern Peru. The group also provides aggregate and construction materials locally, and its stratigraphic framework aids exploration models used by companies such as Compañía de Minas Buenaventura and international partners operating in Peruvian metallogenic provinces.
Although predominantly volcanic and volcaniclastic, certain lacustrine and fluvial horizons within the group have yielded plant macrofossils, palynomorph assemblages, and freshwater mollusks that enable paleoenvironmental reconstructions. Pollen spectra correlate with regional Neogene floras documented in the Altiplano-Puna plateau records and provide insight into climate shifts contemporaneous with global Miocene events such as the Miocene Climatic Optimum. Vertebrate remains are rare but occasional findings permit correlation with continental faunas described from stratigraphic units in the Pampean region and other South American Neogene continental deposits.
Investigation of the Moquegua succession dates to early 20th-century geological surveys by Peruvian and international geologists, with systematic mapping intensified by institutions such as the Instituto Geológico Minero y Metalúrgico and collaborations with universities including the National University of San Agustín and the University of San Marcos. Key contributions include stratigraphic synthesis, radiometric dating campaigns, and regional tectonic syntheses published in national geological congresses and journals. Recent remote sensing, geochemical fingerprinting, and basin analysis integrated with field mapping continue to refine correlations with adjacent units like the Yura Group and to resolve links to broader Andean geodynamic models developed by research groups at institutions such as Geoscience Australia and Smithsonian Institution.
Category:Geologic groups of South America Category:Neogene geology of South America Category:Geology of Peru