The Pacho Formation (Spanish: Limolitas de Pacho, Kslp) is a geological formation of the Altiplano Cundiboyacense, Eastern Ranges of the Colombian Andes. The formation consisting of alternating siltstones and shales with siderite concretions dates to the Middle Cretaceous period; Late Albian to Cenomanian epochs and has an approximate thickness of 1,050 metres (3,440 ft).

Pacho Formation
Stratigraphic range: Late Albian-Cenomanian
~102–97 Ma
TypeGeological formation
Unit ofVilleta Group
UnderliesSimijaca Formation
OverliesHiló Formation
Thickness~1,050 m (3,440 ft)
Lithology
PrimarySiltstone
OtherShale
Location
Coordinates4°27′07″N 74°03′20″W / 4.45194°N 74.05556°W / 4.45194; -74.05556
RegionAltiplano Cundiboyacense
Eastern Ranges, Andes
Country Colombia
Type section
Named forPacho
Named byUlloa
LocationPacho
Year defined1982
Coordinates4°27′07″N 74°03′20″W / 4.45194°N 74.05556°W / 4.45194; -74.05556
RegionCundinamarca
Country Colombia

Paleogeography of Northern South America
105 Ma, by Ron Blakey

Etymology

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The formation was defined and named in 1982 by Ulloa after Pacho, Cundinamarca.[1]

Description

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Lithologies

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The Pacho Formation has an approximate thickness of 1,050 metres (3,440 ft), and is characterised by a sequence of alternating siltstones and shales with siderite concretions.[1]

Stratigraphy and depositional environment

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The Pacho Formation, pertaining to the Villeta Group, partly overlies and is partly lateral equivalent with the Hiló Formation and is partly overlain by and partly time equivalent with the Simijaca Formation. The age has been estimated to be Late Albian to Cenomanian. Stratigraphically, the formation is time equivalent with the Une Formation. The formation has been deposited in an outer marine platform environment.[1]

Outcrops

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Type locality of the Pacho Formation to the northwest of the Bogotá savanna

The Pacho Formation is found around its type locality near Pacho.[1]

Regional correlations

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See also

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  Geology of the Eastern Hills
  Geology of the Ocetá Páramo
  Geology of the Altiplano Cundiboyacense

References

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  1. ^ a b c d Acosta & Ulloa, 2002, p.45

Bibliography

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  • Acosta Garay, Jorge E.; Ulloa Melo, Carlos E. (2002), Mapa Geológico del Departamento de Cundinamarca - 1:250,000 - Memoria explicativa, INGEOMINAS, pp. 1–108, retrieved 2017-04-26
  • Villamil, Tomas (2012), Chronology Relative Sea Level History and a New Sequence Stratigraphic Model for Basinal Cretaceous Facies of Colombia, Society for Sedimentary Geology (SEPM), pp. 161–216

Maps

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