Earth:Conejo Formation

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Short description: Fossiliferous geological formation in the Eastern Ranges of the Colombian Andes
Conejo Formation
Stratigraphic range: Turonian-Santonian
~90–83.6 Ma
TypeGeological formation
Unit ofVilleta Group
UnderliesGuadalupe Group
OverliesLa Frontera Formation
Thicknessup to 1,022 m (3,353 ft)
Lithology
PrimarySandstone, shale
OtherLimestone
Location
Coordinates [ ⚑ ] : 5°35′40.7″N 73°12′59.6″W / 5.594639°N 73.216556°W / 5.594639; -73.216556
RegionAltiplano Cundiboyacense
Eastern Ranges, Andes
Country Colombia
Type section
Named forEl Conejo Hill
Named byRenzoni
LocationToca, Boyacá
Year defined1981
Coordinates [ ⚑ ] 5°35′40.7″N 73°12′59.6″W / 5.594639°N 73.216556°W / 5.594639; -73.216556
RegionCundinamarca, Boyacá
Country Colombia
Blakey 090Ma - COL.jpg
Paleogeography of Northern South America
90 Ma, by Ron Blakey

The Conejo Formation (Spanish: Formación Conejo, K2C, Kscn) is a fossiliferous geological formation of the Altiplano Cundiboyacense, Eastern Ranges of the Colombian Andes. The uppermost unit of the Villeta Group, a sequence of shales and sandstones dates to the Late Cretaceous period; Turonian, Coniacian and Santonian epochs, and has a maximum thickness of 1,022 metres (3,353 ft).

Etymology

The formation was named in 1967 and published in 1981 by Renzoni, named after El Conejo Hill in Pontezuela, Toca, Boyacá, west of the Copa Reservoir.[1][2]

Description

Lithologies

The Conejo Formation is characterised by a sequence of calcareous sandstones, containing ammonites, shales and the uppermost part sandstone and limestone banks.[3] In the Conejo Formation, fossils of Protopholoe colombiana, Archaeglobigerina blowi, Dicarinella concavata, Dicarinella primitiva, Sigalitruncana sigali, Marginotruncana sp. ct. M. renzi, Marginotruncana angusticarenata, Marginotruncana sp. cf. M.sinuosa, Rosita tornicata, Heterohelix globulosa, Heterohelix reussi, Whiteinella inornata, Hedbergella sp., and the ammonites Gloriaceras correai, Protexamites cucaitaense and Codazziceras scheibei have been found.[4][5][6]

Stratigraphy and depositional environment

The Conejo Formation is the uppermost unit of the Villeta Group.[7] It overlies the La Frontera Formation and is overlain by the Guadalupe Group. The age has been estimated on the basis of ammonites to be ranging from Turonian to Santonian.[8] Stratigraphically, the lower part of the formation is time equivalent with the upper part of the Chipaque,[8] and Loma Gorda Formations.[7]

Outcrops

Lua error in Module:Location_map at line 522: Unable to find the specified location map definition: "Module:Location map/data/Altiplano Cundiboyacense" does not exist. The type locality of the Conejo Formation is located close to El Conejo Hill in Pontezuela, Toca, Boyacá.[2] Other outcrops of the Conejo Formation have been noted in Cucaita,[4][5] the urban areas of Boyacá and Ventaquemada, around the Puente de Boyacá, south of Pesca, west of Siachoque,[9] surrounding Chiquinquirá and Ubaté,[10] between Chivatá and Oicatá,[2] east of Paipa,[11] west of Tibacuy,[12] north and south of Albán, southeast of Cachipay, east of Anolaima, and San Antonio del Tequendama, Cundinamarca.[13]

Regional correlations

See also

Featured article candidate Geology of the Eastern Hills
B-Class article Geology of the Ocetá Páramo
C-Class article Geology of the Altiplano Cundiboyacense

References

  1. Montoya & Reyes, 2005, p.29
  2. 2.0 2.1 2.2 Acosta & Ulloa, 2001, p.43
  3. Montoya & Reyes, 2005, p.30
  4. 4.0 4.1 Luque et al., 2015
  5. 5.0 5.1 Tchegliakova & Pérez, 1995
  6. Acosta & Ulloa, 2002, p.48
  7. 7.0 7.1 Acosta & Ulloa, 2002, p.22
  8. 8.0 8.1 Montoya & Reyes, 2005, p.34
  9. Plancha 191, 1998
  10. Plancha 190, 2009
  11. Planchas 171 & 191, 2005
  12. Plancha 246, 1998
  13. Plancha 227, 1998

Bibliography

Maps

External links