Cura-Mallín Group ( es, Grupo Cura-Mallín) is a heterogeneous group of volcano-sedimentary

formation Formation may refer to: Linguistics * Back-formation, the process of creating a new lexeme by removing or affixes * Word formation, the creation of a new word by adding affixes Mathematics and science * Cave formation or speleothem, a secondar ...

s of Oligocene-

Miocene The Miocene ( ) is the first epoch (geology), 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 mea ...

age,

Colhuehuapian The Colhuehuapian age is a period of geologic time (21.0–17.5 Ma) within the Early Miocene epoch of the Neogene, used more specifically within the SALMA classification in South America. It follows the Deseadan and precedes the Santacrucian a ...

Laventan The Laventan ( es, Laventense) age is a period of geologic time (13.8 to 11.8 Ma) within the Middle Miocene epoch of the Neogene, used more specifically within the SALMA classification in South America. It follows the Colloncuran and precedes th ...

in the SALMA classification, in south-central

Chile Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the east a ...

and nearby parts 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, th ...

.Pedroza et al., 2017 The sediments belonging to the group were deposited in a

lacustrine A lake is an area filled with water, localized in a basin, surrounded by land, and distinct from any river or other outlet that serves to feed or drain the lake. Lakes lie on land and are not part of the ocean, although, like the much larger ...

environment Environment most often refers to: __NOTOC__ * Natural environment, all living and non-living things occurring naturally * Biophysical environment, the physical and biological factors along with their chemical interactions that affect an organism or ...

and alongside rivers in an intra-arc basin.Suárez & Emparan, 1995 Southeast of Laguna del Laja Cura-Mallín Group has a thickness of more than . The sediments making up the group deposited in an interval between 22 and 8 million years ago. The outcrops of Cura-Mallín Group are found along a north-south elongate area. The group is considered an equivalent of

Abanico Formation Abanico Formation ( es, Formación Abanico) is a thick sedimentary formation exposed in the Andes of Central Chile. The formation has been deposited in a timespan from the Eocene to the Miocene. Abanico Formation's contact with the overlying M ...

, either as a southern extension or as a lateral equivalent of that formation.Flynn et al., 2008

Stratigraphy and members

Various subdivision schemes have been proposed for the Cura-Mallín unit since the 1980s. In 1983, Niemeyer and Muñoz identified two members; the Río Queuco Member, overlain by the Malla Malla Member. In two publications published in 1995 and 1997, Suárez and Emperan divided Cura-Mallín Formation in two

diachronous In geology, a diachronism (Greek ''dia'', "through" + ''chronos'', "time" + ''-ism''), or diachronous deposit, is a sedimentary rock formation in which the material, although of a similar nature, varies in age with the place where it was deposited. ...

members: Guapitrío and Río Pedregoso. Utgé ''et al.'' (2009) proposed instead a subdivision into an upper Arroyo Pincheira Member and a lower Lumabia Member.Utgé et al., 2009 In a 2017 revision the Cura-Mallín, formerly a formation, was redefined as a group given its great variety of lithologies. The Guapitrío, Río Pedregoso members of Suárez and Emperan became formations according to this scheme. In addition the new scheme include the Mitrauquén Formation that overlies both the Guapitrío and Río Pedregoso Formations as a third formation in the group.

Cura-Mallín Basin

A number of geologists consider Cura-Mallín Basin, the

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 subside ...

where the formation deposited, an extensional basin that developed on the western fringes of the much larger

Neuquén Basin Neuquén Basin ( es, Cuenca Neuquina) is a sedimentary basin covering most of Neuquén Province in Argentina. The basin originated in the Jurassic and developed through alternating continental and marine conditions well into the Tertiary. The bas ...

, while others consider it a back-arc basin. In the Upper Miocene the sedimentary basin was inverted.Radic, 2010 Relative to other nearby sedimentary basins of Miocene and Oligocene age Cura-Mallín Basin has been more researched.Franzese et al., 2011

Fossil content

The group contains abundant mammal fossils including bony fishes, birds and mammals such as

rodent Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are n ...

marsupial Marsupials are any members of the mammalian infraclass Marsupialia. All extant marsupials are endemic to Australasia, Wallacea and the Americas. A distinctive characteristic common to most of these species is that the young are carried in a ...

Mylodontidae Mylodontidae is a family of extinct South American and North American ground sloths within the suborder Folivora of order Pilosa, living from around 23 million years ago (Mya) to 11,000 years ago. This family is most closely related to another f ...

s and

Notoungulata Notoungulata is an extinct order of mammalian ungulates that inhabited South America from the early Paleocene to the Holocene, living from approximately 61 million to 11,000 years ago. Notoungulates were morphologically diverse, with forms resemb ...

Economic geology

The proximity of the Cura-Mallín Group to the stratovolcanoes of Tolhuaca and

Lonquimay Lonquimay is a town and commune in the Malleco Province of southern Chile's Araucanía Region. Transport It is the terminus of an abandoned broad gauge railway project which supporters cited as the most practical railway route through the An ...

has made it a reservoir of geothermal energy of interest. Of all units the Rucañanco Member of Guapitrio Formation has been judged to have the most promising reservoir potential.

References

Bibliography

* * * * * * * {{DEFAULTSORT:Cura-Mallin Formation Geologic groups of South America Geologic formations of Chile Geologic formations of Argentina Miocene Series of South America Oligocene Series of South America Laventan Colloncuran Friasian Santacrucian Colhuehuapian Neogene Chile Paleontology in Chile Geology of Araucanía Region Geology of Biobío Region Geology of Maule Region Geology of Neuquén Province