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Subachoque Formation

Geological formation in South America From Wikipedia, the free encyclopedia

Subachoque Formation
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The Subachoque Formation (Spanish: Formación Subachoque, Q1su) is a geological formation of the Bogotá savanna, Altiplano Cundiboyacense, Eastern Ranges of the Colombian Andes. The formation consists mainly of sandy shales and lignite with sandstone beds. The Subachoque Formation dates to the Quaternary period; Early to Middle Pleistocene epoch (from approximately 2.5 to 1 Ma), and has a maximum thickness of 150 metres (490 ft). It is the lowermost formation of the lacustrine and fluvio-glacial sediments of Lake Humboldt.

Quick Facts Type, Underlies ...
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Etymology

The formation was first defined and named by Helmens and Van der Hammen in 1995 after Subachoque, Cundinamarca.[1]

Description

Lithologies

The Subachoque Formation consists mainly of sandy shales, some organic, with lignite and sandstone beds.[1]

Stratigraphy and depositional environment

The Subachoque Formation is the lowermost of the lagunal and alluvial sequence of the Bogotá savanna. In parts, it conformably overlies the Tilatá Formation and other parts unconformably the Cretaceous Guadalupe Group and the Paleogene Guaduas, Cacho, Bogotá, and Regadera Formations. The Subachoque Formation is overlain by other Quaternary deposits of Lake Humboldt. The age has been estimated to be Early to Middle Pleistocene based on fission track analysis, with reported ages between 2.5 and 1 Ma.[2] The depositional environment has been interpreted as lacustrine and fluvio-glacial with alluvial fans.[1]

Outcrops

Thumb
Subachoque Formation
Type locality of the Subachoque Formation on the northwestern Bogotá savanna

The Subachoque Formation is found at its type locality in the western flank of the synclinal of Subachoque and in the western flank of the synclinal of Guasca.[1] The deposition of the Subachoque Formation postdates the main reverse movement of the Bogotá Fault.[3]

Regional correlations

More information Ma, Age ...
Legend
  • group
  • important formation
  • fossiliferous formation
  • minor formation
  • (age in Ma)
  • proximal Llanos (Medina)[note 1]
  • distal Llanos (Saltarin 1A well)[note 2]

See also

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

Notes

  1. based on Duarte et al. (2019)[40], García González et al. (2009),[41] and geological report of Villavicencio[42]
  2. based on Duarte et al. (2019)[40] and the hydrocarbon potential evaluation performed by the UIS and ANH in 2009[43]

References

Further reading

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