Puncoviscana Formation

Coordinates: 24°00′S 64°00′W / 24.0°S 64.0°W / -24.0; -64.0
Source: Wikipedia, the free encyclopedia.
Puncoviscana Formation
Ma
Type
Formation
UnderliesMesón Group
Lithology
PrimaryShale, sandstone, conglomerate, limestone, slate, schist
Location
LocationBetween Río de la Plata-Pampia Craton & Arequipa Massif
Coordinates24°00′S 64°00′W / 24.0°S 64.0°W / -24.0; -64.0
RegionCatamarca, Jujuy, La Rioja, Salta & Tucumán Provinces
Tarija Department
Country Argentina
 Bolivia
ExtentCordillera Oriental
Type section
Named forPuncoviscana
Named byTurner
Year defined1960
Puncoviscana Formation is located in Argentina
Puncoviscana Formation

Puncoviscana Formation (

formation of sedimentary and metasedimentary rocks Late Ediacaran and Lower Cambrian age, estimated at between 700 and 535 Ma, that crop out in the Argentine Northwest. Most of the formation lies in Jujuy, Salta and Tucumán Province albeit some authors extend the formation further south to the Sierras Pampeanas near Córdoba.[1]

There are various tectonic interpretations on the origin and type of sedimentary basin that accumulated Puncoviscana Formations sediments. An early interpretation was that the sediments originated from a passive marginal basin of the ancient continent Gondwana. Others suggested an intra-cratonic rift or aulacogen basin between Río de la Plata-Pampia Craton and Arequipa Massif. Yet other hypotheses revolve around the idea that the Puncoviscana Formation is related to a terrane called Pampia that accreted to Gondwana causing the closure of a sea in the way.[1]

Stratigraphy, lithology and fossils

The formation includes rocks such as shales, sandstones, conglomerates, limestones, slates and schists. Stratigraphically, the upper boundary of the Puncoviscana Formation is the Tilcarian unconformity, which is overlain by Cambrian and Ordovician sedimentary rocks of the Mesón Group that extend across the Argentine Northwest and Bolivia.[1][2][3]

Fossil content

Among the fossils found in the formation are:[1]

Ichnofossils

Tectonic interpretations of the Puncoviscana Basin

Paleogeographic reconstruction of Gondwana (in yellow) during the time of the Pampean orogeny, around 550 Ma

The Puncoviscana Basin was the

paleogeographic position of the Puncoviscana Basin in relation to the events of the Pampean orogeny
.

The Pampean orogeny is believed by some geologists to be associated with the

Arequipa-Antofalla Craton from the Río de la Plata and Guaporé cratons. Following this interpretation the aulacogen would have closed during the Pampean orogeny.[4]

A 2011 study argues that the Puncoviscana Formation deposited in either a

forearc basin or a trench-slope basin associated with a volcanic arc in the western margin of Gondwana.[6] The same study suggest that a Puncoviscana Ocean formed in the Neoproterozoic as the Arequipa-Antofalla terrane drifted away from the Amazonian continent. The opening of the Puncoviscana Ocean probably preceded the opening of the Iapetus Ocean with the Iapetus Ocean being separated from the Puncoviscana Ocean by the Arequipa-Antofalla terrane. By the time of the opening of Iapetus Ocean Puncoviscana ocean was likely being closed.[6]

See also

References

  1. ^ a b c d Aceñolaza, Florencio; Guillermo, Aceñolaza (2005). "La formación Puncoviscana y unidades estratigráficas vinculadas en el neoproterozoico - Cámbrico temprano del noroeste argentino" (PDF). Latin American Journal of Sedimentology and Basin Analysis (in Spanish). 12 (2). Asociación Argentina de Sedimentología: 65–87. Retrieved 7 December 2015.
  2. ^ Gaucher, Claudio; Bossi, Jorge; Blanco, Gonzalo (2010). "Paleogeography". In Gaucher, Claudio; Sial, Alcides; Haverson, Galen (eds.). Neoproterozoic-cambrian tectonics, global change and evolution: a focus on south western Gondwana. Elsevier. p. 137.
  3. ^ Aceñolaza, G.F. (2003). "The Cambrian System in Northwestern Argentina: stratigraphical and palaeontological framework". Geologica Acta. 1 (1): 23–39. Retrieved 28 December 2015.
  4. ^ a b c Aceñolaza, Florencio G.; Toselli, Alejandro (2010). "The Pampean Orogen: Ediacaran-Lower Cambrian Evolutionary History of Central and Northwest Region of Argentina". In Gaucher, Claudio; Sial, Alcides; Haverson, Galen (eds.). Neoproterozoic-cambrian tectonics, global change and evolution: a focus on south western Gondwana. Elsevier. pp. 239–254.
  5. hdl:11336/92729
    . Retrieved 15 December 2015.
  6. ^
    hdl:11336/84857
    .

Further reading
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