Lautaro Formation

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Lautaro Formation
Stratigraphic range: Toarcian–Aalenian,
~184–170 Ma
Strata of the Lautaro Formation outcropping at La Puerta locality
TypeGeological formation
UnderliesQuebrada Monardes Formation
OverliesLa Ternera Formation
Thickness~2,600 m (8,500 ft)
Lithology
PrimaryLimestone
OtherSandstone
Location
RegionAtacama Region
CountryChile
ExtentLautaro Basin
Type section
Named forLautaro

The Lautaro Formation is sedimentary and fossiliferous geological formation that largely crops out near Copiapó (Atacama Region), Chile. It is dated back to the Jurassic period (Toarcian through Aalenian stages). The lithology of the formation comprises limestone and sandstone, formed in marine settings. The Lautaro Formation preserves a marine fossil record, representing molluscs (bivalves, gastropods) and marine reptiles (metriorhynchids, plesiosaurs).[1][2][3]

The strata of the Lautaro Formation and its basin of deposition (the Lautaro Basin) have been subject to intense tectonic movement during the Mesozoic, producing large-scale stratigraphic discontinuity and tectonic inversion.[2][4][5][6][7]

Strata of the Lautaro Formation exposed at the Tranque Lautaro
Fossils of Gryphaea and Lithotrochus at La Puerta
Fossils of Gryphaea at La Puerta

Paleobiota of the Lautaro Formation

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Ammonites

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Genus Species Material Locality Unit Notes Images
Arieticeras Indeterminate Not specified.[8] Tranque Lautaro A hildoceratid ammonite.
Oxynoticeras O. oxynotum Not specified.[8] Tranque Lautaro An oxynoticeratid ammonite.

Bivalves

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Genus Species Material Locality Unit Notes Images
Gryphaea G. darwini Partial and complete shells.[2] La Puerta, Tranque Lautaro A gryphaeid bivalve.
Weyla W. alata Partial and complete shells.[8][2] La Puerta, Tranque Lautaro A pectinid bivalve.

Brachiopods

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Genus Species Material Locality Unit Notes Images
Rhynchonella R. variabilis Not specified.[8] Tranque Lautaro A rhynchonellid brachiopod.

Crocodyliformes

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Genus Species Material Locality Unit Notes Images
Metriorhynchus Indeterminate Partial skull.[1] Quebrada La Iglesia Upper part A metriorhynchid.

Gastropods

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Genus Species Material Locality Unit Notes Images
Lithotrochus L. humboldtii Partial and complete shells.[2] La Puerta, Tranque Lautaro A trochid gastropod.

Plesiosaurs

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Genus Species Material Locality Unit Notes Images
Plesiosauria indet. Indeterminate Three vertebrae.[3] Quebrada La Iglesia Upper part A plesiosaur.

See also

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References

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  1. ^ a b Gasparini, Z.; Vignaud, P.; Chong, G. (2000). "The Jurassic Thalattosuchia (Crocodyliformes) of Chile: a paleobiogeographic approach" (PDF). Bulletin de la Société Géologique de France. 171 (6): 657−664. doi:10.2113/171.6.657. hdl:10915/123708.
  2. ^ a b c d e Martínez, F.; Arriagada, C.; Mpodozis, C.; Peña, M. (2012). "The Lautaro Basin: A record of inversion tectonics in northern Chile" (PDF). Andean Geology. 39 (2): 258−278. doi:10.5027/andgeoV39n2-a04. hdl:10533/138798.
  3. ^ a b Otero, R. A.; Acuña, S. S.; Rojas, J.; Rojas, O. (2020). "Primer registro de un plesiosaurio del Jurásico Medio de Ojo Opache, Calama, norte de Chile, con comentarios sobre registros similares en la Región de Atacama". Museo de Historia Natural y Cultural del Desierto de Atacama (Ocassional Publication N° 2): 1−57.
  4. ^ Martínez, F.; Arriagada, C.; Valdivia, R.; Deckart, K.; Peña, M. (2015). "Geometry and kinematics of the Andean thick-skinned thrust systems: Insights from the Chilean Frontal Cordillera (28°–28.5°S), Central Andes". Journal of South American Earth Sciences. 64: 307−324. doi:10.1016/j.jsames.2015.05.001.
  5. ^ Martínez, F.; Arriagada, C.; Peña, M.; Deckart, K.; Charrier, R. (2016). "Tectonic styles and crustal shortening of the Central Andes "Pampean" flat-slab segment in northern Chile (27–29°S)". Tectonophysics. 667: 144−162. doi:10.1016/j.tecto.2015.11.019.
  6. ^ Martínez, F.; Bonini, M.; Montanari, D.; Corti, G. (2016). "Tectonic inversion and magmatism in the Lautaro Basin, northern Chile, Central Andes: A comparative approach from field data and analog models". Journal of Geodynamics. 94–95: 68−83. doi:10.1016/j.jog.2016.02.003.
  7. ^ Peña, M.; Quiroga, R.; Fuentes, G.; Arellano, M.; Norambuena, J.; Bascuñán, S. (2023). "Kinematic analysis of the mesozoic - Early Cenozoic deformation in the paipote basin (27°10′S)". Journal of South American Earth Sciences. 129: 104543. doi:10.1016/j.jsames.2023.104543.
  8. ^ a b c d Segerstrom, K. (1967). "Geology and Ore Deposits of Central Atacama Province, Chile". Geological Society of America Bulletin. 78 (3): 305−318.
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