Английская Википедия:Chacarilla Formation

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Шаблон:Short description Шаблон:Infobox rockunit The Chacarilla Formation (Шаблон:Lang-es) is an Oxfordian to Early Cretaceous geologic formation of the Tarapacá Basin in northern Chile, close to the border with Bolivia. The marine and fluvial formation preserves several dinosaur trackways and has been declared a Natural Sanctuary (Шаблон:Lang-es) in 2004.[1]

Description

Файл:Stratigraphic column - Chacarilla Formation, Chile.jpg
Stratigraphic column of the formation

The formation comprises a sequence of rhythmically alternating shales and red sandstones with a minimum thickness of Шаблон:Convert. The lower part of the formation was deposited under marine conditions and the upper part in a meandering river floodplain and point bar environment. Paleocurrent analysis demonstrated a flow direction towards the west, northwest and west-northwest.[2]

The formation contains ichnofossils of theropods and ornithopods, occurring in the Early Cretaceous upper part of the formation, which is marked by an angular unconformity, overlain by volcanic and clastic rocks of the Late Cretaceous to Early Paleocene Cerro Empexa Formation.[2] The top of the formation is not younger than Aptian.[3]

Шаблон:Clearleft

Fossil content

Файл:Dinosaur tracksite - Chacarilla Formation, Chile.jpg
Dinosaur tracksite of the Chacarilla Formation

Fossil stegosaur, sauropod and theropod tracks and fossil flora have been reported from the formation.[4]

The fourteen trackways of the Chacarilla III tracksite consist of 76 individual footprints. Two of the trackways consist of large ornithopod footprints (average footprint length Шаблон:Convert and average width Шаблон:Convert). Two other trackways consist of small theropod footprints (less than Шаблон:Convert long).[5] The other ten trackways were made by large theropods (footprint length more than Шаблон:Convert). The large theropod tracks are tri− and tetradactyl, mesaxonic, and have lengths and widths between Шаблон:Convert and Шаблон:Convert, respectively. Nearly all digit impressions possess claw marks, but they lack clear impressions of digital pads. The stride length varies between Шаблон:Convert. The speed of the dinosaurs leaving the tracks is estimated at Шаблон:Convert.[6]

Additionally, in the Jurassic part of the formation, fossil flora was reported, containing fossils of Posidonomya, Perisphinctes,[7] Baiera sp., Brachyphyllum sp., Cladophlebis sp., Dictyophyllum sp., Equisetites sp., Nilsonia sp., Pterophyllum sp., Ptilophyllum sp., Taeniopteris sp., and Filicales.[8]

See also

References

Шаблон:Reflist

Bibliography

Further reading

  • C. G. Oliver and C.A. Menéndez. 1968. Geología de la Quebrada Juan de Morales, Tarapacá, Chile y su flora Jurásica. Terceras Jornadas Geologicas Argentinas 163-171
  • R. J. Dingman and C. Galli O. 1965. Geology and ground-water resources of the Pica area, Tarapacá Province, Chile. United States Geological Survey Bulletin 1189:1-113

Шаблон:Geology of Chile

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  1. ↑ Шаблон:In lang Quebrada de Chacarilla - Consejo de Monumentos Naturales de Chile
  2. ↑ 2,0 2,1 Rubilar Rogers et al., 2008, p.177
  3. ↑ Moreno et al., 2012, p.75
  4. ↑ Weishampel et al., 2004, pp.517-607
  5. ↑ Moreno et al., 2012, p.77
  6. ↑ Moreno et al., 2012, p.79
  7. ↑ Leonardi, 1994, p.65
  8. ↑ Quebrada Juan de Morales at Fossilworks.org
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