Simijaca Formation
Stratigraphic range: Cenomanian-Turonian ~100–90 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Type	Geological formation
Unit of	Villeta Group
Underlies	La Frontera Formation
Overlies	Chiquinquirá Sst., Churuvita Fm., Hiló Fm., Pacho Fm.
Thickness	up to 693 m (2,270 ft)
Lithology
Primary	Mudstone
Other	Shale, sandstone, limestone
Location
Coordinates	5°29′15″N 73°50′55″W / 5.48750°N 73.84861°W / 5.48750; -73.84861
Region	Altiplano Cundiboyacense Eastern Ranges, Andes
Country	Colombia
Type section
Named for	Simijaca
Named by	Ulloa & Rodríguez
Location	South of Simijaca
Year defined	1991
Coordinates	5°29′15″N 73°50′55″W / 5.48750°N 73.84861°W / 5.48750; -73.84861
Region	Cundinamarca, Boyacá
Country	Colombia
Thickness at type section	432 metres (1,420 ft)
Paleogeography of Northern South America 90 Ma, by Ron Blakey

The Simijaca Formation (Spanish: Formación Simijaca, K₂S, Kss) is a geological formation of the Altiplano Cundiboyacense, Eastern Ranges of the Colombian Andes. The predominantly mudstone formation dates to the Late Cretaceous period; Turonian and Cenomanian epochs, and has a maximum thickness of 693 metres (2,274 ft).

The formation was defined and named in 1991 by Ulloa and Rodríguez after Simijaca, Cundinamarca.^[1]

The Simijaca Formation is characterised by a sequence of mudstones, grey and black shales with sandstone and limestone intercalations.^[1][2]

The Simijaca Formation conformably overlies the Chiquinquirá Sandstone, and the Hiló and Pacho Formations, and is overlain by the La Frontera Formation.^[3] The age has been estimated to be Turonian,^[1] or Cenomanian.^[4] Stratigraphically, the formation is time equivalent with the Chipaque Formation.^[5] The formation has been deposited in an open marine platform setting.^[6] The deposition is represented by a maximum flooding surface.^[7]

Type locality of the Simijaca Formation on the Altiplano Cundiboyacense

The Simijaca Formation is apart from its type locality in the Quebrada Don Lope,^[2] found at surface in the north of the Bogotá savanna, in the Tabio anticlinal, along the road Ubaté-Carmen de Carupa,^[8] at the western and eastern flanks of the Aponsentos-Chiquinquirá Synclinal,^[9] near Tena, south of Anolaima and Cachipay,^[10] and between Anapoima and Granada.^[11]

Geology of the Eastern Hills

Geology of the Ocetá Páramo

Geology of the Altiplano Cundiboyacense

• Acosta Garay, Jorge; Ulloa Melo, Carlos E. (2001), Geología de la Plancha 208 Villeta - 1:100,000 (PDF), INGEOMINAS, pp. 1–84, retrieved 2017-03-23
• García González, Mario; Mier Umaña, Ricardo; Cruz Guevara, Luis Enrique; Vásquez, Mauricio (2009), Informe Ejecutivo - evaluación del potencial hidrocarburífero de las cuencas colombianas, Universidad Industrial de Santander, pp. 1–219
• Montoya Arenas, Diana María; Reyes Torres, Germán Alfonso (2005), Geología de la Sabana de Bogotá, INGEOMINAS, pp. 1–104
• 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

• Ulloa, Carlos E; Rodríguez, Erasmo (2009), Plancha 170 - Vélez - 1:100,000, INGEOMINAS, p. 1, retrieved 2017-06-06
• Fuquen M., Jaime A; Osorno M, José F. (2009), Plancha 190 - Chiquinquirá - 1:100,000, INGEOMINAS, p. 1, retrieved 2017-06-06
• Ulloa, Carlos; Acosta, Jorge (1998), Plancha 208 - Villeta - 1:100,000, INGEOMINAS, p. 1, retrieved 2017-06-06
• Montoya, Diana María; Reyes, Germán (2009), Plancha 209 - Zipaquirá - 1:100,000, INGEOMINAS, p. 1, retrieved 2017-06-06
• Ulloa, Carlos E; Rodríguez, Erasmo; Acosta, Jorge E. (1998), Plancha 227 - La Mesa - 1:100,000, INGEOMINAS, p. 1, retrieved 2017-06-06
• Acosta, Jorge E.; Ulloa, Carlos E. (1998), Plancha 246 - Fusagasugá - 1:100,000, INGEOMINAS, p. 1, retrieved 2017-06-06

• Gómez, J.; Montes, N.E.; Nivia, Á.; Diederix, H. (2015), Plancha 5-09 del Atlas Geológico de Colombia 2015 – escala 1:500,000, Servicio Geológico Colombiano, p. 1, retrieved 2017-03-23