The Villeta Group
: Grupo Villeta
) is a geological group
of the Eastern Ranges
of the Colombian Andes
, to the west of the Altiplano Cundiboyacense
. The group, a sequence of shales
, is subdivided into various formations; Conejo
, La Frontera
, El Peñón
, and Trincheras
, and dates to the Cretaceous
epochs. The group stretches out across four departments
, from Huila
in the south, through Cundinamarca
to southern Santander
in the north. The upper part of the Villeta Group is time-equivalent with the La Luna Formation
of the Middle Magdalena Valley
(VMM) and Sierra Nevada del Cocuy
, the Oliní
and Güagüaquí Groups
of the Guaduas
and the Chipaque Formation
of the Altiplano Cundiboyacense
. The lower part has been correlated with the Simití
and Paja Formations
of the VMM, the upper Tibasosa
and Fómeque Formations
of the Altiplano Cundiboyacense and the Capacho
and upper Río Negro Formations
of the Sierra Nevada del Cocuy.
The group was published in 1892 by Hettner and named after its type locality Villeta on the western flanks of the Eastern Ranges of the Colombian Andes.
The sequence comprises an alternation of sandstones, shales and limestones and the lithologies and lateral facies variations are described in detail in the various formations comprising the group. Mineralizations of zinc, cadmium and molybdenum have been found in the Villeta Group.
The Villeta Group overlies the La Naveta Formation and is overlain by the Guadalupe Group. The age has been estimated to be Aptian-Coniacian and the unit is subdivided into the Conejo, La Frontera, Simijaca, Hiló, Pacho Formations, the Chiquinquirá Sandstone, and the Capotes, Socotá, El Peñón, and Trincheras Formations. The core extent of the group has been defined by Cáceres and Etayo in 1969, running from Apulo in the south to Muzo in the north. The Villeta Group has been deposited in a marine environment and the organic rich shales and pelagic limestones and cherts of the Villeta Group and equivalent units comprise 60-70% of the Cretaceous record in the Eastern Ranges. They provide a good opportunity to study the interactions between tectonics eustatic sea level and sedimentation that regulate relative sea level in a basin.
The formations of the Villeta Group are apart from its type locality near Villeta, found in other parts of the western flanks of the Eastern Ranges, stretching from Huila in the south to southern Santander in the north.
This page was last edited on 13 May 2018, at 15:19.
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