The Chaco Basin ( es, Cuenca Chaco, es, Cuenca Chaco Paranaense or es, Cuenca Chaco-Paraná) is a major

sedimentary basin Sedimentary basins are region-scale depressions of the Earth's crust where subsidence has occurred and a thick sequence of sediments have accumulated to form a large three-dimensional body of sedimentary rock. They form when long-term subsidence ...

in Central South America around the borders of

Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, t ...

Bolivia , image_flag = Bandera de Bolivia (Estado).svg , flag_alt = Horizontal tricolor (red, yellow, and green from top to bottom) with the coat of arms of Bolivia in the center , flag_alt2 = 7 × 7 square p ...

and

Paraguay Paraguay (; ), officially the Republic of Paraguay ( es, República del Paraguay, links=no; gn, Tavakuairetã Paraguái, links=si), is a landlocked country in South America. It is bordered by Argentina to the south and southwest, Brazil to th ...

. The basin forms part of the larger

Paraná Basin The Paraná Basin ( pt, Bacia do Paraná, es, Cuenca del Paraná) is a large cratonic sedimentary basin situated in the central-eastern part of South America. About 75% of its areal distribution occurs in Brazil, from Mato Grosso to Rio Grande ...

. Superficially, the Chaco Basin is an

alluvial Alluvium (from Latin ''alluvius'', from ''alluere'' 'to wash against') is loose clay, silt, sand, or gravel that has been deposited by running water in a stream bed, on a floodplain, in an alluvial fan or beach, or in similar settings. Al ...

basin composed of land-derived (in contrast to marine sediments) material, mostly fine sand and clays of

Paleogene The Paleogene ( ; also spelled Palaeogene or Palæogene; informally Lower Tertiary or Early Tertiary) is a geologic period and system that spans 43 million years from the end of the Cretaceous Period million years ago (Mya) to the beginning of ...

Neogene The Neogene ( ), informally Upper Tertiary or Late Tertiary, is a geologic period and system that spans 20.45 million years from the end of the Paleogene Period million years ago (Mya) to the beginning of the present Quaternary Period Mya. ...

and Quaternary age. On deeper levels the Paraguayan Chaco is made up by four sub-basins, the Pirizal, Pilar, Carandaity and Curupaity basins.

Stratigraphy

The basin is part of the megaregional

, of which it occupies its western portion. The basin is subdivided into the Western Chaco (''Chaco Occidental'') and Eastern Chaco (''Chaco Oriental''). The

Paleozoic The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon. The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838 by combining the Greek words ''palaiós'' (, "old") and ' ...

stratigraphy of the Chaco Basin comprises the Middle to Late Carboniferous Sachayoj Formation, the

Late Carboniferous Late may refer to: * LATE, an acronym which could stand for: ** Limbic-predominant age-related TDP-43 encephalopathy, a proposed form of dementia ** Local-authority trading enterprise, a New Zealand business law ** Local average treatment effe ...

Charata Formation Charata is a city in the province A province is almost always an administrative division within a country or sovereign state, state. The term derives from the ancient Roman ''Roman province, provincia'', which was the major territorial and adm ...

and the

Early Permian 01 or '01 may refer to: * The year 2001, or any year ending with 01 * The month of January * 1 (number) Music * 01'' (Richard Müller album), 2001 * ''01'' (Son of Dave album), 2000 * ''01'' (Urban Zakapa album), 2011 * ''O1'' (Hiroyuki Sawano ...

Chacabuco Formation Chacabuco is one of the many abandoned nitrate or "saltpeter" towns ("oficinas salitreras" in Spanish) in the Atacama Desert of northern Chile. Other nitrate towns of the Atacama Desert include Humberstone and Santa Laura Saltpeter Works. Unl ...

.Cuenca Chaco Paranense
/ref> The

cover contains the

Late Miocene The Late Miocene (also known as Upper Miocene) is a sub-epoch of the Miocene Epoch made up of two stages. The Tortonian and Messinian stages comprise the Late Miocene sub-epoch, which lasted from 11.63 Ma (million years ago) to 5.333 Ma. The ...

Paraná Formation,Brea et al., 2013, p.28 the

Late Pleistocene The Late Pleistocene is an unofficial age in the international geologic timescale in chronostratigraphy, also known as Upper Pleistocene from a stratigraphic perspective. It is intended to be the fourth division of the Pleistocene Epoch within ...

( Lujanian in the SALMA classification) Chaco Formation,Quebrada Agua Blanca
at

Fossilworks Fossilworks is a portal which provides query, download, and analysis tools to facilitate access to the Paleobiology Database, a large relational database assembled by hundreds of paleontologists from around the world. History Fossilworks was cre ...

.orgMapa Geológico del Paraguay, 1986, p.42 also described as

Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', " ...

Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recent" ...

,Filí, 2001, p.28 and the substratum-forming Fortín Tres Pozos Formation in the

Formosa Province Formosa Province () is a province in northeastern Argentina, part of the Gran Chaco Region. Formosa's northeast end touches Asunción, Paraguay, and the province borders the provinces of Chaco and Salta to its south and west, respectively. ...

of northern Argentina.Zurita et al., 2009, p.279Soibelzon et al., 2010, p.315

References

Bibliography

* * * * * {{Sedimentary basins of Argentina Sedimentary basins of Argentina Sedimentary basins of Bolivia Sedimentary basins of Paraguay Foreland basins * Geology of Santa Cruz Department (Bolivia) Geology of Tarija Department