Pacho Formation

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

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).

Etymology

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

Description

Lithologies

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

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

Pacho Formation is located in the Bogotá savanna
Pacho Formation
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

Cretaceous stratigraphy of the central Colombian Eastern Ranges
Age Paleomap VMM Guaduas-Vélez W Emerald Belt Villeta anticlinal Chiquinquirá-
Arcabuco
Tunja-
Duitama
Altiplano Cundiboyacense El Cocuy
Maastrichtian Umir Córdoba Seca eroded Guaduas Colón-Mito Juan
Umir Guadalupe
Campanian Córdoba
Oliní
Santonian La Luna Cimarrona - La Tabla La Luna
Coniacian Oliní Villeta Conejo Chipaque
Güagüaquí Loma Gorda undefined La Frontera
Turonian Hondita La Frontera Otanche
Cenomanian Simití hiatus La Corona Simijaca Capacho
Pacho Fm. Hiló - Pacho Churuvita Une Aguardiente
Albian Hiló Chiquinquirá Tibasosa Une
Tablazo Tablazo Capotes - La Palma - Simití Simití Tibú-Mercedes
Aptian Capotes Socotá - El Peñón Paja Fómeque
Paja Paja El Peñón Trincheras Río Negro
La Naveta
Barremian
Hauterivian Muzo Cáqueza Las Juntas
Rosablanca Ritoque
Valanginian Ritoque Furatena Útica - Murca Rosablanca hiatus Macanal
Rosablanca
Berriasian Cumbre Cumbre Los Medios Guavio
Tambor Arcabuco Cumbre
Sources


See also

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

References

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

Bibliography

  • 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