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| Golondrina Formation | |
|---|---|
| Name | Golondrina Formation |
| Type | Geological formation |
| Period | Paleogene |
| Age | Eocene–Oligocene |
| Region | Patagonia |
| Country | Argentina |
| Lithology | Conglomerate, sandstone, mudstone |
| Namedfor | Golondrina |
Golondrina Formation is a Paleogene continental stratigraphic unit exposed in northern Patagonia, Argentina. It comprises a succession of continental clastic rocks that record fluvial, lacustrine, and palustrine sedimentation during paleoclimatic and tectonic changes associated with Andean uplift. The formation has yielded important vertebrate and plant remains that contribute to biostratigraphic correlations across South America.
The formation is part of the Andean foreland context affected by the tectonic evolution linked to the Andes and the South American Plate, showing relationships with regional structures such as the Neuquén Basin, the Golfo San Jorge Basin, and the Bermejo Basin. Lithologies include coarse conglomerates, medium- to fine-grained sandstones, siltstones, and mudstones with paleosols and volcanic ash layers that indicate syn-sedimentary input from proximal highlands related to the Subandean Zone and the Sierras Pampeanas. Detrital provenance studies reference crystalline and volcanic sources including the Patagonian Batholith and older metamorphic complexes correlated with the Gondwana breakup. Diagenetic overprint records cementation by calcite and silica with secondary iron oxyhydroxides reflecting paleoredox conditions similar to sequences in the Chubut Province and adjacent basins.
Stratigraphic relations place the unit within a package deposited above Cretaceous and Paleogene marine successions and below younger Neogene continental deposits. The Golondrina succession shows lateral facies changes comparable to those documented in the Río Negro Province and in stratigraphic columns used for correlation with the Santa Cruz Formation, the Sarmiento Formation, and the Chichinales Formation. Key marker beds include tuffaceous horizons useful for radiometric dating and regional correlation with volcanic events recorded in the Patagonia volcanic province and ash layers tied to chronostratigraphic frameworks like the South American Land Mammal Ages. Unconformities reflect phases of basin inversion linked to Andean orogenic pulses recorded in the Mendoza Province and La Pampa Province.
Fossil assemblages recovered include vertebrates, plants, and trace fossils that inform biostratigraphy and paleoecology. Mammalian remains show affinities with taxa known from the Deseadan and Colhuehuapian South American Land Mammal Ages, with genera comparable to those found in the Sarmiento Formation and Santa Cruz Formation faunas. Recovered small mammals, including notoungulates and rodents, parallel records from the Itaboraí Formation and correlate with taxa described from the Paleogene of South America. Avian remains and crocodilian teeth provide links to other Patagonian localities such as Pampa Castillo and Puesto Viejo. Paleobotanical material—pollen, leaves, and wood—correlates with floras known from the La Ensenada and Pilcaniyeu floristic assemblages, aiding reconstructions of Paleogene vegetation dynamics. Ichnofossils include burrows and trackways comparable to those from the Sierra de la Ventana region.
Sedimentologic and paleontologic evidence indicates fluvial meandering to braided systems with intermittent lacustrine and palustrine environments analogous to depositional models applied in the Neuquén and Golfo San Jorge basins. Paleosol horizons and coalified plant remains suggest seasonally waterlogged floodplain conditions similar to those reconstructed for the Chubut and Río Mayo basins. Vegetation reconstructions from pollen and macrofossils indicate mixed temperate to subtropical floras with affinities to records from the Patagonian steppe margins and Andes-adjacent woodlands, linking to broader paleoclimatic shifts documented across South America during Eocene–Oligocene cooling and Antarctic glaciation onset. Faunal assemblages imply trophic structures comparable to those inferred for contemporaneous sites such as the Félix de Azara and Tiahuanaco records.
Chronostratigraphic data including radiometric ages from tuffs and biostratigraphic markers provide an Eocene to early Oligocene age, allowing correlation with the South American Land Mammal Ages such as the Deseadan and possibly early Tinguirirican. Correlations are drawn to well-studied Patagonian units like the Sarmiento Formation, the Río Turbio Formation, and other Paleogene sequences in Argentina and Chile, as well as comparisons to faunal assemblages from the Bolivia and Peru Paleogene basins. Geochronologic ties to volcanic events recorded in the Andean volcanic arc permit integration into hemispheric paleoclimatic frameworks including links to Antarctic records from Wilkes Land and chronologies used in Paleogene climate reconstructions.
The formation hosts clastic reservoirs and aquifers important for groundwater in local communities of Chubut Province and Río Negro Province. Aggregates and construction-grade sandstones are exploited locally, and paleosol horizons with organic matter have been considered for studies of coalification comparable to minor deposits in the Patagonian coalfields. The tuffaceous layers serve as geochronologic markers useful in regional hydrocarbon exploration workflows tied to the Neuquén Basin petroleum systems and to mineral exploration in the Patagonian Andes. Conservation of fossil sites has attracted paleontological fieldwork coordinated with institutions like the Museo Argentino de Ciencias Naturales and regional universities.
Category:Geologic formations of Argentina