Subachoque Formation
{{short description|Geological formation in South America}}
{{other uses|Subachoque (disambiguation)}}
{{Infobox rockunit
| name = Subachoque Formation
| period = Pleistocene
| age = Early to Mid Pleistocene
~{{fossil range|2.5|1}}
| image =
| imagesize =
| caption =
| type = Geological formation
| prilithology = Shale, lignite
| otherlithology = Sandstone
| unitof =
| subunits =
| underlies = Sabana Formation
| overlies = Tilatá Formation
Guadalupe Gp.
Guaduas Fm., Cacho Fm., Bogotá Fm., Regadera Fm.
| thickness = up to {{convert|150|m|ft|-1}}
| area =
| map = Blakey Pleist - COL.jpg
| map_caption = Paleogeography of the Pleistocene
{{small|by Ron Blakey}}
| location =
| coordinates = {{coord|4|57|17.3|N|74|13|07.5|W|display=inline,title}}
| region = Bogotá savanna, Altiplano Cundiboyacense
Eastern Ranges, Andes
| country = Colombia
| extent =
| namedfor = Subachoque
| namedby = Helmens & Hammen
| year_ts = 1995
| location_ts = Subachoque Synclinal
| coordinates_ts = {{coord|4|57|17.3|N|74|13|07.5|W|display=inline}}
| paleocoordinates_ts =
| region_ts = Cundinamarca
| country_ts = Colombia
| thickness_ts =
}}
The Subachoque Formation ({{langx|es|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 {{convert|150|m|ft}}. It is the lowermost formation of the lacustrine and fluvio-glacial sediments of Lake Humboldt.
Etymology
The formation was first defined and named by Helmens and Van der Hammen in 1995 after Subachoque, Cundinamarca.Montoya & Reyes, 2005, p.69
Description
= Lithologies =
= 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.Montoya & Reyes, 2005, p.71 The depositional environment has been interpreted as lacustrine and fluvio-glacial with alluvial fans.
Outcrops
{{Location map | Bogotá savanna
| width = 250
| lat_deg = 4.954799
| lon_deg = -74.218754
| label =
| float = left
| position = right
| mark = Yellow pog.svg
| marksize = 12
| caption = 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. The deposition of the Subachoque Formation postdates the main reverse movement of the Bogotá Fault.Geological Map Bogotá, 1997
{{clear}}
Regional correlations
{{Stratigraphy of the Llanos Basin}}
See also
{{Portal|Colombia|Geology}}
:{{icon|GAN}} Geology of the Eastern Hills
:{{icon|B}} Geology of the Ocetá Páramo
:{{icon|C}} Geology of the Altiplano Cundiboyacense
Notes
{{reflist|group=note}}
References
{{reflist|30em}}
= Bibliography =
- {{citation |last1=Montoya Arenas |first1=Diana María |last2=Reyes Torres |first2=Germán Alfonso |year=2005 |title=Geología de la Sabana de Bogotá |publisher=INGEOMINAS |pages=1–104}}
== Maps ==
- {{citation |last1=Buitrago |first1=José Alberto |last2=Terraza M. |first2=Roberto |author3-link=Fernando Etayo |last3=Etayo |first3=Fernando |year=1998 |title=Plancha 228 - Santafé de Bogotá Noreste - 1:100,000 |url=https://drive.google.com/open?id=0BwFQPMJEi17QTlNraVVZZ2ZCY0E |publisher=INGEOMINAS |pages=1 |accessdate=2017-06-06}}
- {{citation |last=Various |first=Authors |year=1997 |title=Mapa geológico de Santa Fe de Bogotá – Geological Map Bogotá – 1:50,000 |url=http://seisan.sgc.gov.co/RSNC/Mapa_Geo.pdf |publisher=INGEOMINAS |pages=1 |accessdate=2017-03-16}}
Further reading
- {{citation |last=Guerrero Uscátegui |first=Alberto Lobo |year=1992 |title=Geología e Hidrogeología de Santafé de Bogotá y su Sabana |publisher=Sociedad Colombiana de Ingenieros |pages=1–20}}
External links
- {{citation |last1=Gómez |first1=J. |last2=Montes |first2=N.E. |last3=Nivia |first3=Á. |last4=Diederix |first4=H. |year=2015 |title=Plancha 5-09 del Atlas Geológico de Colombia 2015 – escala 1:500,000 |url=https://www.researchgate.net/publication/309533589 |publisher=Servicio Geológico Colombiano |pages=1 |accessdate=2017-03-16}}
Category:Geologic formations of Colombia