Cura-Mallín Group

Cura-Mallín Group
Stratigraphic range: Upper Oligocene–Middle Miocene
Colhuehuapian-Laventan (SALMA)
Type Geological group
Unit of Cura-Mallín Basin
 Neuquén Basin
Sub-units Various schemes, see text
Underlies Cajón Negro Formation
Trapa Trapa Formation
Overlies Cretaceous granitoids
Jurassic sediments
Thickness more than 1,800 m (5,900 ft)
Lithology
Primary Sandstone, siltstone, shale, breccia, andesite lava
Other Grainstone
Location
Region Araucanía Region, Bío Bío Region, Neuquén Province
Country Chile, Argentina

Cura-Mallín Group (Spanish: Grupo Cura-Mallín) is a heterogeneous group of volcano-sedimentary formations of Oligocene-Miocene age, Colhuehuapian to Laventan in the SALMA classification, in south-central Chile and nearby parts of Argentina.[1][2][3] The group's sediments were deposited in a lake environment and alongside rivers in an intra-arc basin.[1] Southeast of Laguna del Laja Cura-Mallín Group has a thickness of more than 1,800 metres (5,900 ft).[4] The sediments making up the group deposited in an interval between 22 and 8 million years ago.[3]

The Cura-Mallín Group has a north-south elongate form.[4] The group is considered an equivalent of Abanico Formation, either as a southern extension or as a lateral equivalent of that formation.[4]

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 members: Guapitrío and Río Pedregoso. Utgé et al. (2009) proposed instead a subdivision into an upper Arroyo Pincheira Member and a lower Lumabia Member.[2]

In a 2017 revision the Cura-Mallín, formerly a formation, was redefined as a group given its great variety of lithologies.[3] 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 units as a third formation in the group.[3]

Cura-Mallín Basin

A number of geologists consider Cura-Mallín Basin, the sedimentary basin where the formation deposited, an extensional basin that developed on the western fringes of the much larger Neuquén Basin, while others consider it a back-arc basin. In the Upper Miocene the sedimentary basin was inverted.[5] Relative to other nearby sedimentary basins of Miocene and Oligocene age Cura-Mallín Basin has been more researched.[6]

Fossil content

The group contains abundant mammal fossils including bony fishes, birds and mammals such as rodents, marsupials, Mylodontidaes and Notoungulatas.[4]

Group Fossils Notes
MammalsHeteropsomyinae (aff. Acarechimys) sp., Dasyproctidae (aff. Alloiomys) sp., Prolagostomus sp., Caviomorpha indet., Dasypodidae indet., Typotheria indet.
Paedotherium minor, Acarechimys sp., aff. Alloiomys sp., ?Hegetotherium sp., aff. Incamys sp., Luantus sp., Maruchito sp., Prostichomys sp., Protacaremys sp., cf. Protypotherium sp., Sipalocyon sp., Abderitidae indet., Astrapotheria indet., Astrapotheriidae indet., Caviomorpha indet., Dasypodidae indet., Eocardiidae indet., Hegetotheriinae indet., Interatheriinae indet., Pachyrukhinae indet., Toxodontidae indet., Typotheria indet.
Acarechimys sp., Luantus sp., Protacaremys sp., Protypotherium sp., Sipalocyon sp., Echimyidae indet.
FishesNematogenys cuivi

Economic geology

The proximity of the Cura-Mallín Group to the stratovolcanoes of Tolhuaca and Lonquimay 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.[3]

References

  1. 1 2 Suarez, M.; Emparan, C. (1995). "The stratigraphy, geochronology and paleophysiography of a Miocene fresh-water interarc basin, southern Chile". Journal of South American Earth Sciences. 8 (1): 17–31.
  2. 1 2 Utgé, Silvana; Folguera, Andrés; Litvak, Vanesa; Ramos, Víctor A. (2009). "Geología del sector norte de la Cuenca de Cura Mallín en las Lagunas de Epulaufquen, Neuquén". Revista de la Asociación Geológica Argentina (in Spanish). 64 (2): 231–248. Retrieved 4 August 2016.
  3. 1 2 3 4 5 Pedroza, Viviana; Le Roux, Jacobus P.; Gutiérrez, Néstor M.; Vicencio, Vladimir E. (2017). "Stratigraphy, sedimentology, and geothermal reservoir potential of the volcaniclastic Cura-Mallín succession at Lonquimay, Chile". Journal of South American Earth Sciences. 77: 1–20. doi:10.1016/j.jsames.2017.04.011.
  4. 1 2 3 4 Flynn, John .J.; Charrier, Reynaldo; Croft, Darin A.; Gans, Phillip B.; Herriott, Trystan M.; Wertheim, Jill A.; Wyss, André R. (2008). "Chronologic implications of new Miocene mammals from the Cura-Mallín and Trapa Trapa formations, Laguna del Laja area, south central Chile" (PDF). Journal of South American Earth Sciences. 26 (4): 412–423. Retrieved 31 July 2016.
  5. ↑ Radic, Juan Pablo (2010). "Las cuencas cenozoicas y su control en el volcanismo de los Complejos Nevados de Chillan y Copahue-Callaqui (Andes del Sur, 36-39°S)". Andean Geology (in Spanish). 37 (1): 220–246. Retrieved 31 July 2016.
  6. ↑ Franzese, Juan R.; D'Elia, Leandro; Bilmes, Andrés; Muravchik, Martin; Hernández, Mariano (2011). "Superposición de cuencas extensionales y contraccionales oligo-miocenas en el retroarco andino norpatagónico: la Cuenca de Aluminé, Neuquén, Argentina". Andean Geology (in Spanish). 38 (2): 319–334. Retrieved 1 August 2016.
  7. ↑ Cerro los Pinos at Fossilworks.org
  8. ↑ Trapa Trapa East mid-upper beds at Fossilworks.org
  9. ↑ Estero Trapa Trapa West at Fossilworks.org
  10. ↑ Flynn et al., 2008, p.414
  11. ↑ Cerro Rucañanco at Fossilworks.org
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