Pacho Formation

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
RegionAltiplano Cundiboyacense
Eastern Ranges, Andes
Country Colombia
Type section
Named forPacho
Named byUlloa
LocationPacho
Year defined1982
Coordinates4°27′07″N 74°03′20″W
RegionCundinamarca
Country Colombia

Paleogeography of Northern South America
105 Ma, by Ron Blakey

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

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
AgePaleomapVMMGuaduas-VélezW Emerald BeltVilleta anticlinalChiquinquirá-
Arcabuco
Tunja-
Duitama
Altiplano CundiboyacenseEl Cocuy
MaastrichtianUmirCórdobaSecaerodedGuaduasColón-Mito Juan
UmirGuadalupe
CampanianCórdoba
Oliní
SantonianLa LunaCimarrona - La TablaLa Luna
ConiacianOliníConejoChipaque
Güagüaquí
Loma GordaundefinedLa Frontera
TuronianHonditaLa FronteraOtanche
CenomanianSimitíhiatusLa CoronaSimijacaCapacho
Pacho Fm.Hiló - PachoChuruvitaUneAguardiente
AlbianHilóChiquinquiráTibasosaUne
TablazoTablazoCapotes - La Palma - SimitíSimitíTibú-Mercedes
AptianCapotesSocotá - El PeñónPajaFómeque
PajaPajaEl PeñónTrincherasRío Negro
La Naveta
Barremian
HauterivianMuzo
Cáqueza
Las Juntas
RosablancaRitoque
ValanginianRitoqueFuratenaÚtica - MurcaRosablancahiatusMacanal
Rosablanca
BerriasianCumbreCumbreLos MediosGuavio
TamborArcabucoCumbre
Sources

See also

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

References

  1. Acosta & Ulloa, 2002, p.45

Bibliography

Maps

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