# Subachoque Formation

The Subachoque Formation (Spanish: Formación Subachoque, Q$_{1su}$) 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.

## Etymology

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

## Description
### Lithologies

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

### 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. The depositional environment has been interpreted as lacustrine and fluvio-glacial with alluvial fans.

## Outcrops

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.

## Regional correlations

Stratigraphy of the Llanos Basin and surrounding provinces :
| Ma | Age | Regional events | Catatumbo | Cordillera | proximal Llanos | distal Llanos | Putumayo | VSM | Environments | Maximum thickness | Petroleum geology | Notes |
| 0.01 | Holocene | Holocene volcanism Seismic activity | alluvium | alluvium | alluvium | alluvium | alluvium | alluvium | alluvium | | Overburden | |
| 1 | Pleistocene | Pleistocene volcanism Andean orogeny 3 Glaciations | Guayabo | Soatá Sabana | Necesidad | Guayabo | Gigante Neiva | Gigante Neiva | Alluvial to fluvial (Guayabo) | 550 m (1,800 ft) (Guayabo) | Overburden | |
| 2.6 | Pliocene | Pliocene volcanism Andean orogeny 3 GABI | Guayabo | Subachoque | Necesidad | Guayabo | Gigante Neiva | Gigante Neiva | Alluvial to fluvial (Guayabo) | 550 m (1,800 ft) (Guayabo) | Overburden | |
| 5.3 | Messinian | Andean orogeny 3 Foreland | Guayabo | Marichuela | Necesidad | Guayabo | Caimán | Honda | Alluvial to fluvial (Guayabo) | 550 m (1,800 ft) (Guayabo) | Overburden | |
| 13.5 | Langhian | Regional flooding | León | hiatus | Caja | León | Caimán | Honda | Lacustrine (León) | 400 m (1,300 ft) (León) | Seal | |
| 16.2 | Burdigalian | Miocene inundations Andean orogeny 2 | C1 | hiatus | Carbonera C1 | Carbonera C1 | Ospina | Honda | Proximal fluvio-deltaic (C1) | 850 m (2,790 ft) (Carbonera) | Reservoir | |
| 17.3 | Burdigalian | Miocene inundations Andean orogeny 2 | C2 | hiatus | Carbonera C2 | Carbonera C2 | Ospina | Honda | Distal lacustrine-deltaic (C2) | 850 m (2,790 ft) (Carbonera) | Seal | |
| 19 | Burdigalian | Miocene inundations Andean orogeny 2 | C3 | hiatus | Carbonera C3 | Carbonera C3 | Ospina | Honda | Proximal fluvio-deltaic (C3) | 850 m (2,790 ft) (Carbonera) | Reservoir | |
| 21 | Early Miocene | Pebas wetlands | C4 | hiatus | Carbonera C4 | Carbonera C4 | Ospina | Barzalosa | Distal fluvio-deltaic (C4) | 850 m (2,790 ft) (Carbonera) | Seal | |
| 23 | Late Oligocene | Andean orogeny 1 Foredeep | C5 | hiatus | Carbonera C5 | Carbonera C5 | Orito | Orito | Proximal fluvio-deltaic (C5) | 850 m (2,790 ft) (Carbonera) | Reservoir | |
| 25 | Late Oligocene | Andean orogeny 1 Foredeep | C6 | hiatus | Carbonera C6 | Carbonera C6 | Orito | Orito | Distal fluvio-lacustrine (C6) | 850 m (2,790 ft) (Carbonera) | Seal | |
| 28 | Early Oligocene | Andean orogeny 1 Foredeep | C7 | hiatus | C7 | | Pepino | Gualanday | Proximal deltaic-marine (C7) | 850 m (2,790 ft) (Carbonera) | Reservoir | |
| 32 | Oligo-Eocene | Andean orogeny 1 Foredeep | C8 | Usme | C8 | onlap | Pepino | Gualanday | Marine-deltaic (C8) | 850 m (2,790 ft) (Carbonera) | Seal Source | |
| 35 | Late Eocene | Andean orogeny 1 Foredeep | Mirador | Usme | Mirador | Mirador | Pepino | Gualanday | Coastal (Mirador) | 240 m (790 ft) (Mirador) | Reservoir | |
| 40 | Middle Eocene | Andean orogeny 1 Foredeep | Mirador | Regadera | Mirador | Mirador | Pepino | hiatus | Coastal (Mirador) | 240 m (790 ft) (Mirador) | Reservoir | |
| 45 | Middle Eocene | Andean orogeny 1 Foredeep | Mirador | Regadera | Mirador | Mirador | Pepino | hiatus | Coastal (Mirador) | 240 m (790 ft) (Mirador) | Reservoir | |
| 50 | Early Eocene | Andean orogeny 1 Foredeep | Socha | Regadera | Los Cuervos | Los Cuervos | Pepino | hiatus | Deltaic (Los Cuervos) | 260 m (850 ft) (Los Cuervos) | Seal Source | |
| 55 | Late Paleocene | PETM 2000 ppm CO$_2$ | Los Cuervos | Bogotá | Los Cuervos | Los Cuervos | Pepino | Gualanday | Deltaic (Los Cuervos) | 260 m (850 ft) (Los Cuervos) | Seal Source | |
| 60 | Early Paleocene | SALMA | Barco | Guaduas | Barco | Barco | Rumiyaco | Gualanday | Fluvial (Barco) | 225 m (738 ft) (Barco) | Reservoir | |
| 65 | Maastrichtian | KT extinction | Catatumbo | Guadalupe | Guadalupe | Guadalupe | Rumiyaco | Monserrate | Deltaic-fluvial (Guadalupe) | 750 m (2,460 ft) (Guadalupe) | Reservoir | |
| 72 | Campanian | End of rifting | Colón-Mito Juan | Guadalupe | Guadalupe | Guadalupe | Rumiyaco | Monserrate | Deltaic-fluvial (Guadalupe) | 750 m (2,460 ft) (Guadalupe) | Reservoir | |
| 83 | Santonian | End of rifting | Colón-Mito Juan | Guadalupe | Guadalupe | Guadalupe | Villeta/Güagüaquí | Villeta/Güagüaquí | Deltaic-fluvial (Guadalupe) | 750 m (2,460 ft) (Guadalupe) | Reservoir | |
| 86 | Coniacian | End of rifting | Colón-Mito Juan | Guadalupe | Guadalupe | Guadalupe | Villeta/Güagüaquí | Villeta/Güagüaquí | Deltaic-fluvial (Guadalupe) | 750 m (2,460 ft) (Guadalupe) | Reservoir | |
| 89 | Turonian | Cenomanian-Turonian anoxic event | La Luna | Chipaque | Gachetá | hiatus | Villeta/Güagüaquí | Villeta/Güagüaquí | Restricted marine (all) | 500 m (1,600 ft) (Gachetá) | Source | |
| 93 | Cenomanian | Rift 2 | La Luna | Chipaque | Gachetá | hiatus | Villeta/Güagüaquí | Villeta/Güagüaquí | Restricted marine (all) | 500 m (1,600 ft) (Gachetá) | Source | |
| 100 | Albian | Rift 2 | La Luna | Une | Une | hiatus | Caballos | Caballos | Deltaic (Une) | 500 m (1,600 ft) (Une) | Reservoir | |
| 113 | Aptian | Rift 2 | Capacho | Fómeque | Une | hiatus | Motema | Yaví | Open marine (Fómeque) | 800 m (2,600 ft) (Fómeque) | Source (Fóm) | |
| 125 | Barremian | High biodiversity | Aguardiente | Paja | Une | hiatus | Motema | Yaví | Shallow to open marine (Paja) | 940 m (3,080 ft) (Paja) | Reservoir | |
| 129 | Hauterivian | Rift 1 | Tibú- Mercedes | Las Juntas | hiatus | hiatus | Motema | Yaví | Deltaic (Las Juntas) | 910 m (2,990 ft) (Las Juntas) | Reservoir (LJun) | |
| 133 | Valanginian | Rift 1 | Río Negro | Cáqueza Macanal Rosablanca | hiatus | hiatus | Motema | Yaví | Restricted marine (Macanal) | 2,935 m (9,629 ft) (Macanal) | Source (Mac) | |
| 140 | Berriasian | Rift 1 | Girón | Cáqueza Macanal Rosablanca | hiatus | hiatus | Motema | Yaví | Restricted marine (Macanal) | 2,935 m (9,629 ft) (Macanal) | Source (Mac) | |
| 145 | Tithonian | Break-up of Pangea | Jordán | Arcabuco | Buenavista Batá | hiatus | Saldaña | Saldaña | Alluvial, fluvial (Buenavista) | 110 m (360 ft) (Buenavista) | "Jurassic" | |
| 150 | Early-Mid Jurassic | Passive margin 2 | La Quinta | Montebel Noreán | hiatus | hiatus | Saldaña | Saldaña | Coastal tuff (La Quinta) | 100 m (330 ft) (La Quinta) | "Jurassic" | |
| 201 | Late Triassic | Passive margin 2 | Mucuchachi | Montebel Noreán | hiatus | hiatus | Payandé | Payandé | | | "Jurassic" | |
| 235 | Early Triassic | Pangea | | hiatus | hiatus | hiatus | | | | | "Paleozoic" | |
| 250 | Permian | Pangea | | hiatus | hiatus | hiatus | | | | | "Paleozoic" | |
| 300 | Late Carboniferous | Famatinian orogeny | | hiatus | hiatus | hiatus | | Cerro Neiva | | | "Paleozoic" | |
| 340 | Early Carboniferous | Fossil fish Romer's gap | | Cuche (355-385) | Farallones | hiatus | | Cerro Neiva | | Deltaic, estuarine (Cuche) | "Paleozoic" | 900 m (3,000 ft) (Cuche) |
| 360 | Late Devonian | Passive margin 1 | Río Cachirí (360-419) | Cuche (355-385) | Farallones | | | Ambicá | Alluvial-fluvial-reef (Farallones) | 2,400 m (7,900 ft) (Farallones) | "Paleozoic" | |
| 390 | Early Devonian | High biodiversity | Floresta (387-400) El Tíbet | Floresta (387-400) El Tíbet | | | | Ambicá | Shallow marine (Floresta) | 600 m (2,000 ft) (Floresta) | "Paleozoic" | |
| 410 | Late Silurian | Silurian mystery | Floresta (387-400) El Tíbet | Floresta (387-400) El Tíbet | | | | | | | "Paleozoic" | |
| 425 | Early Silurian | Silurian mystery | hiatus | hiatus | hiatus | hiatus | hiatus | hiatus | | | "Paleozoic" | |
| 440 | Late Ordovician | Rich fauna in Bolivia | San Pedro (450-490) | | Duda | | | | | | "Paleozoic" | |
| 470 | Early Ordovician | First fossils | San Pedro (450-490) | Busbanzá (>470±22) ChuscalesOtengá | Guape | | Río Nevado | HígadoAgua Blanca Venado (470-475) | | | "Paleozoic" | |
| 488 | Late Cambrian | Regional intrusions | Chicamocha (490-515) | Quetame | Ariarí | | SJ del Guaviare (490-590) | San Isidro | | | "Paleozoic" | |
| 515 | Early Cambrian | Cambrian explosion | | Quetame | | | SJ del Guaviare (490-590) | San Isidro | | | "Paleozoic" | |
| 542 | Ediacaran | Break-up of Rodinia | | pre-Quetame | | post-Parguaza | SJ del Guaviare (490-590) | El Barro | Yellow: allochthonous basement (Chibcha Terrane) Green: autochthonous basement (Río Negro-Juruena Province) | | Basement | |
| 600 | Neoproterozoic | Cariri Velhos orogeny | Bucaramanga (600-1400) | pre-Quetame | | post-Parguaza | pre-Guaviare | El Barro | Yellow: allochthonous basement (Chibcha Terrane) Green: autochthonous basement (Río Negro-Juruena Province) | | Basement | |
| 800 | Neoproterozoic | Snowball Earth | Bucaramanga (600-1400) | pre-Quetame | | post-Parguaza | pre-Guaviare | El Barro | Yellow: allochthonous basement (Chibcha Terrane) Green: autochthonous basement (Río Negro-Juruena Province) | | Basement | |
| 1000 | Mesoproterozoic | Sunsás orogeny | Bucaramanga (600-1400) | pre-Quetame | Ariarí (1000) | post-Parguaza | pre-Guaviare | La Urraca (1030-1100) | Yellow: allochthonous basement (Chibcha Terrane) Green: autochthonous basement (Río Negro-Juruena Province) | | Basement | |
| 1300 | Mesoproterozoic | Rondônia-Juruá orogeny | Bucaramanga (600-1400) | pre-Quetame | pre-Ariarí | Parguaza (1300-1400) | pre-Guaviare | Garzón (1180-1550) | Yellow: allochthonous basement (Chibcha Terrane) Green: autochthonous basement (Río Negro-Juruena Province) | | Basement | |
| 1400 | Mesoproterozoic | Rondônia-Juruá orogeny | pre-Bucaramanga | pre-Quetame | pre-Ariarí | | pre-Guaviare | Garzón (1180-1550) | Yellow: allochthonous basement (Chibcha Terrane) Green: autochthonous basement (Río Negro-Juruena Province) | | Basement | |
| 1600 | Paleoproterozoic | Rondônia-Juruá orogeny | pre-Bucaramanga | pre-Quetame | pre-Ariarí | Maimachi (1500-1700) | pre-Guaviare | pre-Garzón | Yellow: allochthonous basement (Chibcha Terrane) Green: autochthonous basement (Río Negro-Juruena Province) | | Basement | |
| 1800 | Paleoproterozoic | Tapajós orogeny | pre-Bucaramanga | pre-Quetame | pre-Ariarí | Mitú (1800) | pre-Guaviare | pre-Garzón | Yellow: allochthonous basement (Chibcha Terrane) Green: autochthonous basement (Río Negro-Juruena Province) | | Basement | |
| 1950 | Paleoproterozoic | Transamazonic orogeny | pre-Bucaramanga | pre-Quetame | pre-Ariarí | pre-Mitú | pre-Guaviare | pre-Garzón | Yellow: allochthonous basement (Chibcha Terrane) Green: autochthonous basement (Río Negro-Juruena Province) | | Basement | |
| 2200 | Paleoproterozoic | Columbia | pre-Bucaramanga | pre-Quetame | pre-Ariarí | pre-Mitú | pre-Guaviare | pre-Garzón | Yellow: allochthonous basement (Chibcha Terrane) Green: autochthonous basement (Río Negro-Juruena Province) | | Basement | |
| 2530 | Archean | Carajas-Imataca orogeny | pre-Bucaramanga | pre-Quetame | pre-Ariarí | pre-Mitú | pre-Guaviare | pre-Garzón | Yellow: allochthonous basement (Chibcha Terrane) Green: autochthonous basement (Río Negro-Juruena Province) | | Basement | |
| 3100 | Archean | Kenorland | pre-Bucaramanga | pre-Quetame | pre-Ariarí | pre-Mitú | pre-Guaviare | pre-Garzón | Yellow: allochthonous basement (Chibcha Terrane) Green: autochthonous basement (Río Negro-Juruena Province) | | Basement | |
| Sources ||||||||||||||

### Legend

* group
* important formation
* fossiliferous formation
* minor formation
* (age in Ma)
* proximal Llanos (Medina)
* distal Llanos (Saltarin 1A well)