| Subachoque Formation | |
| Period: | Pleistocene |
| Age: | Early to Mid Pleistocene ~ |
| Type: | Geological formation |
| Prilithology: | Shale, lignite |
| Otherlithology: | Sandstone |
| Underlies: | Sabana Formation |
| Overlies: | Tilatá Formation Guadalupe Gp. Guaduas Fm., Cacho Fm., Bogotá Fm., Regadera Fm. |
| Thickness: | up to 150m (490feet) |
| Map: | Blakey Pleist - COL.jpg |
| Coordinates: | 4.9548°N -74.2188°W |
| Region: | Bogotá savanna, Altiplano Cundiboyacense Eastern Ranges, Andes |
| Namedfor: | Subachoque |
| Namedby: | Helmens & Hammen |
| Year Ts: | 1995 |
| Location Ts: | Subachoque Synclinal |
| Coordinates Ts: | 4.9548°N -74.2188°W |
| Region Ts: | Cundinamarca |
The Subachoque Formation (Spanish; Castilian: 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 150m (490feet). It is the lowermost formation of the lacustrine and fluvio-glacial sediments of Lake Humboldt.
The formation was first defined and named by Helmens and Van der Hammen in 1995 after Subachoque, Cundinamarca.[1]
The Subachoque Formation consists mainly of sandy shales, some organic, with lignite and sandstone beds.[1]
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]
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]
Geology of the Eastern Hills
Geology of the Ocetá Páramo
Geology of the Altiplano Cundiboyacense