Macanal Formation

The Macanal Formation or Macanal Shale ( es, (Formación) Lutitas de Macanal, Kilm, K1m) is a fossiliferous geological formation of the Altiplano Cundiboyacense and Tenza Valley in the Eastern Ranges of the Colombian Andes. The predominantly organic shale formation dates to the Early Cretaceous period; Berriasian to Valanginian epochs and has a maximum thickness of . The Macanal Formation contains numerous levels of fossiliferous abundances. Bivalves, ammonites and fossil flora have been found in the formation.

The formation is a source rock for oil and gas in the Eastern Cordillera Basin and adjacent Llanos Basin foothills and provides emeralds in the vicinity of Macanal, after which the formation is named.

Etymology

The formation was defined and named in 1979 by Rodríguez and Ulloa after Macanal, Cundinamarca.Acosta & Ulloa, 2002, p.51 The name Macanal is either derived from the Muysccubun word ''Macana'', meaning garrote, or from the ''Macana'' palm tree.Official website Macanal
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Description

Lithologies

The Macanal Formation has a maximum thickness of , and is characterised by a sequence of micaceous organic shales,Rodríguez & Solano, 2000, p.47 with calcite veins and gypsum occurrences intercalated in the formation. The Macanal Formation contains high values of TOC.Acosta & Ulloa, 2002, p.52 In the Eastern Cordillera Basin and the adjacent foothills of the Llanos Basin, the Macanal Formation is a source rock for oil and gas.García González et al., 2009, p.49 In the vicinity of Macanal, the formation provides emeralds.Uribe, 1960, p.5ANM, 2015, p.1

Stratigraphy and depositional environment

The Macanal Formation, a unit of the Cáqueza Group, concordantly overlies the Guavio, Santa Rosa, Ubalá, Chivor and Batá Formations,Terraza et al., 2013, p.110 and is concordantly overlain by the Las Juntas Formation. The age has been estimated to be Berriasian to Valanginian. Stratigraphically, the formation is time equivalent with the Mercedes, Tambor, Rosablanca, Murca and La Naveta Formations.Villamil, 2012, p.168 The formation has been deposited in a shallow marine environment in an enclosed basin, with as provenance areas the Santander High and the Guiana Shield.Villamil, 2012, p.165 The Macanal Formation is part of the syn-rift sequence of eastern Colombia.Schütz, 2012, p.26

Fossil content

The Macanal Formation contains numerous levels of fossiliferous abundances. Bivalves, ammonites and flora have been found in the formation.Patiño et al., 2011, p.45 Ammonites of '' Substeueroceras cf. mutabile'', '' Sarasinella cf. hondana'', '' Subalpinites sp.'', '' Berriasela sp.'', '' Neocomites cf. wichmanni'', '' Olcostephanus sp.'', '' Olcostephanus cf. atherstoni'', '' Favrella cf. colombiana'', '' Acanthodiscus sp.'' have been registered in the formation, as well as bivalves of '' Corbis (Sphaera) cf. corrugata'', '' Trigonia cf. hondana'', '' Trigonia (Buchotrigonia) cf. abrupta'', '' Trigonia (Notoscabrotrigonia) cf. tocaimaana'', and '' Exogyra cf. boussingaulti''.Piraquive et al., 2011, p.204 Analysis of the deformation registered in ammonite fossils has helped in understanding the tectonic history of the Llanos foothills of the Eastern Ranges.Montaña Cárdenas, 2015, p.52

Outcrops

The Macanal Formation is apart from its type locality in the Batá River canyon,Rodríguez & Solano, 2000, p.46Plancha 210, 2010 found in the Cravo Sur anticline, east of the Ocetá Páramo,Plancha 172, 1998 in the Desespero Synclinal in the southern and northern parts of Labranzagrande,Plancha 193, 1992Pinto Valderrama et al., 2010, p.44 around Páez and Campohermoso, in the eastern part of Gama, bordering the Guavio Reservoir,Plancha 228, 1998 and in the Servitá Synclinal, west of Villavicencio.Plancha 266, 1998 The Macanal Formation crops out along the road between Bogotá and Villavicencio and is there heavily fractured and folded. The Macanal Formation is the most extensive formation around Cáqueza,Patiño et al., 2011, p.44 and Gachalá, Cundinamarca.Terraza et al., 2013, p.101

The Pajarito Fault thrusts the Macanal Formation on top of the Fómeque Formation to the east of Lake Tota,Plancha 192, 1998 and the Chámeza Fault thrusts the Macanal Formation on top of the overlying Las Juntas Formation around Chámeza, Casanare.Plancha 211, 2009 The Ubaque Fault forms the contact between the Fómeque Formation and the Macanal Formation,Patiño et al., 2011, p.102 while the Las Mercedes Fault puts the Quetame Group in contact with the Macanal Formation near Quetame,Patiño et al., 2011, p.110 as does the San Juanito Fault.Patiño et al., 2011, p.114 The Servitá Fault forms the contact between the Guatiquía Redbeds and the Macanal Formation,Patiño et al., 2011, p.122 and the Upín Fault, part of the same system puts the Macanal Formation in contact with the Tertiary Palmichal Group.Patiño et al., 2011, p.123 At this contact, brines are extracted from the formation.Patiño et al., 2011, p.125

Regional correlations

See also

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

Notes and references

Notes

References

Bibliography

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Maps

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External links

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{{Colombian emeralds, state=expanded

Geologic formations of Colombia
Cretaceous Colombia
Lower Cretaceous Series of South America
Berriasian Stage
Valanginian Stage
Shale formations
Shallow marine deposits
Source rock formations
Mining in Colombia
Formations
Fossiliferous stratigraphic units of South America
Paleontology in Colombia
Formations
Formations
Formations
Formations
Muysccubun