# Simijaca Formation

The Simijaca Formation (Spanish: Formación Simijaca, K$_2$S, Kss) is a geological formation of the Altiplano Cundiboyacense, Eastern Ranges of the Colombian Andes. The predominantly mudstone formation dates to the Late Cretaceous period; Turonian and Cenomanian epochs, and has a maximum thickness of 693 metres (2,274 ft).

## Etymology

The formation was defined and named in 1991 by Ulloa and Rodríguez after Simijaca, Cundinamarca.

## Description
### Lithologies

The Simijaca Formation is characterised by a sequence of mudstones, grey and black shales with sandstone and limestone intercalations.

### Stratigraphy and depositional environment

The Simijaca Formation conformably overlies the Chiquinquirá Sandstone, and the Hiló and Pacho Formations, and is overlain by the La Frontera Formation. The age has been estimated to be Turonian, or Cenomanian. Stratigraphically, the formation is time equivalent with the Chipaque Formation. The formation has been deposited in an open marine platform setting. The deposition is represented by a maximum flooding surface.

## Outcrops

The Simijaca Formation is apart from its type locality in the Quebrada Don Lope, found at surface in the north of the Bogotá savanna, in the Tabio anticlinal, along the road Ubaté-Carmen de Carupa, at the western and eastern flanks of the Aponsentos-Chiquinquirá Synclinal, near Tena, south of Anolaima and Cachipay, and between Anapoima and Granada.

## Regional correlations

Cretaceous stratigraphy of the central Colombian Eastern Ranges :
| Age | VMM | Guaduas-Vélez | Guaduas-Vélez | W Emerald Belt | W Emerald Belt | Villeta anticlinal | Villeta anticlinal | Chiquinquirá- Arcabuco | Tunja- Duitama | Altiplano Cundiboyacense | Altiplano Cundiboyacense | El Cocuy |
| Maastrichtian | Umir | Córdoba | Córdoba | Seca | Seca | eroded | eroded | Guaduas | Guaduas | Guaduas | Guaduas | Colón-Mito Juan |
| Maastrichtian | Umir | Córdoba | Córdoba | Umir | Umir | eroded | eroded | Guadalupe | Guadalupe | Guadalupe | Guadalupe | | | | Colón-Mito Juan |
| Campanian | Umir | Córdoba | Córdoba | Córdoba | Córdoba | | eroded | eroded | Guadalupe | Guadalupe | Guadalupe | Guadalupe | Colón-Mito Juan |
| Colón-Mito Juan ||
| Santonian | La Luna | Cimarrona - La Tabla | Cimarrona - La Tabla | Oliní | Oliní | eroded | eroded | Guadalupe | Guadalupe | Guadalupe | Guadalupe | La Luna |
| Coniacian | La Luna | Oliní | Oliní | Oliní | Oliní | Villeta | Conejo | Conejo | Chipaque | Chipaque | Chipaque | | | La Luna |
| Coniacian | La Luna | Güagüaquí | Loma Gorda | undefined | undefined | Villeta | La Frontera | La Frontera | | Chipaque | Chipaque | Chipaque | La Luna |
| Turonian | La Luna | Güagüaquí | Hondita | La Frontera | Otanche | Villeta | La Frontera | La Frontera | Chipaque | Chipaque | Chipaque | La Luna |
| Cenomanian | Simití | hiatus | hiatus | La Corona | Otanche | Villeta | Simijaca | Simijaca | Chipaque | Chipaque | Chipaque | Capacho |
| Cenomanian | Simití | hiatus | hiatus | Pacho Fm. | Otanche | Villeta | Hiló - Pacho | Churuvita | Une | Une | Une | Aguardiente |
| Albian | Simití | hiatus | hiatus | Hiló | Otanche | Villeta | Hiló - Pacho | Chiquinquirá | Tibasosa | Une | Une | | Aguardiente |
| Albian | Tablazo | hiatus | hiatus | Tablazo | Tablazo | Villeta | Capotes - La Palma - Simití | Simití | Tibasosa | Une | Une | Tibú-Mercedes |
| Aptian | Tablazo | hiatus | hiatus | Capotes | Capotes | Villeta | Socotá - El Peñón | Paja | Tibasosa | Fómeque | Fómeque | | Tibú-Mercedes |
| Aptian | Paja | hiatus | hiatus | Paja | El Peñón | Villeta | Trincheras | Paja | Tibasosa | Fómeque | Fómeque | Río Negro |
| Río Negro ||
| Barremian | Paja | hiatus | hiatus | Paja | El Peñón | La Naveta | La Naveta | Paja | Tibasosa | Fómeque | Fómeque | Río Negro |
| Hauterivian | Paja | hiatus | hiatus | Paja | Muzo | La Naveta | La Naveta | Paja | Tibasosa | Cáqueza | Las Juntas | Río Negro |
| Hauterivian | Rosablanca | hiatus | hiatus | Paja | Muzo | La Naveta | La Naveta | Ritoque | Tibasosa | Cáqueza | Las Juntas | Río Negro |
| Valanginian | Rosablanca | hiatus | hiatus | Ritoque | Furatena | Útica - Murca | Útica - Murca | Rosablanca | hiatus | Cáqueza | Macanal | Río Negro |
| Valanginian | Rosablanca | hiatus | hiatus | Rosablanca | Furatena | Útica - Murca | Útica - Murca | Rosablanca | hiatus | Cáqueza | Macanal | Río Negro |
| Berriasian | Cumbre | hiatus | hiatus | Cumbre | Cumbre | Útica - Murca | Útica - Murca | Los Medios | hiatus | Cáqueza | Guavio | Río Negro |
| Berriasian | Tambor | hiatus | hiatus | Arcabuco | Arcabuco | Útica - Murca | Útica - Murca | Cumbre | hiatus | Cáqueza | Guavio | Río Negro |
| Sources ||||||||||||||