Earth:Río Cachirí Group

Short description: Geological group in the Venezuelan Andes

Río Cachirí Group Stratigraphic range: Devonian 419–360 Ma PreЄ Є O S D C P T J K Pg N
Type	Geological group
Unit of	Cesar-Ranchería Basin, Serranía del Perijá
Sub-units	Caño Grande Fm., Caño del Oeste Fm., Campo Chico Fm., Los Guineos Fm.
Underlies	Carboniferous sequence
Overlies	Perijá Formation
Thickness	~1,100 m (3,600 ft) (Colombia) 2,438 m (7,999 ft) (Venezuela)
Lithology
Primary	Shale, sandstone
Other	Limestone
Location
Coordinates
Region	Cesar, La Guajira Zulia
Country	Colombia Venezuela
Extent	~110 km (68 mi) (Venezuela)
Type section
Named for	Río Cachirí
Named by	Liddle
Location	Mara
Year defined	1928
Coordinates	[ ⚑ ] 10°50′03″N 72°14′23″W
Region	Zulia
Country	Venezuela
Thickness at type section	2,438 m (7,999 ft)
Paleogeography of the Middle Devonian 380 Ma, by Stampfli & Borel

The Río Cachirí Group (Spanish: Grupo Río Cachirí, PZc) is a geological group of the Cesar-Ranchería Basin, Colombia and the Serranía del Perijá of the northernmost Colombian and Venezuelan Andes. The group of shales, sandstones and limestones is of Devonian age and has a maximum thickness in the Venezuelan section of 2,438 metres (7,999 ft). The group contains abundant fauna; crinoids, bryozoa, brachiopods and molluscs have been found in the group.

Etymology and definition

The formation was defined by Liddle in 1928 in Río Cachirí, part of Mara, Zulia, in the Venezuelan part of the Serranía del Perijá, and the same author subdivided the group into three formations in 1943. In 1972, Bowen added a fourth formation to the group.

Description

Lithologies

The group contains black, grey and red shales, grey micaceous sandstones, quartzitic sandstones and red and bluish grey limestones.

Stratigraphy and correlation

The Río Cachirí Group, dated to span the Devonian, is subdivided into the Caño Grande, Caño del Oeste, Campo Chico and Los Guineos Formations. The maximum thickness has been recorded in Venezuela, with 2,438 metres (7,999 ft), while the thickness on the Colombian side of the range does not exceed 1,100 metres (3,600 ft). The group is recognised along a section of approximately 110 kilometres (68 mi) in the Venezuelan terrain. The group unconformably overlies the Perijá Formation and is overlain by an unnamed Carboniferous sequence. The Río Cachirí Group is time-equivalent with the Floresta and Cuche Formations of the Floresta Massif, Altiplano Cundiboyacense and the Quetame Group of the Eastern Ranges. The sediments of the Río Cachirí Group were deposited in an epicontinental sea at the edge of the Paleo-Tethys Ocean.

Fossil content

The group contains abundant fossils of crinoids, bryozoa, brachiopods and molluscs as Acrospirifer olssoni, Spirifer kingi, Leptaena boyaca, Fenestella venezuelansis, Neospirifer latus, Composita subtilita, Phricodrotis planoconvexa and Pecten sp.

Outcrops

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Type locality of the Río Cachirí Group in Venezuela

Apart from its type locality on the eastern flank of the Serranía del Perijá in Zulia, Venezuela, the formation is also found in other parts of the mountain range, on the Colombian western side in the east of San Diego and Curumaní, Cesar.

See also

Geology of the Eastern Hills

Geology of the Ocetá Páramo

Geology of the Altiplano Cundiboyacense

References

Bibliography

• Ayala Calvo, Rosa Carolina. 2009. Análisis tectonoestratigráfico y de procedencia en la Subcuenca de Cesar: Relación con los sistemas petroleros (MSc. thesis), 1–255. Universidad Simón Bolívar. Accessed 2017-06-14.
• García González, Mario; Ricardo Mier Umaña; Luis Enrique Cruz Guevara, and Mauricio Vásquez. 2009. Informe Ejecutivo - evaluación del potencial hidrocarburífero de las cuencas colombianas, 1–219. Universidad Industrial de Santander.
• Hernández Ferrer, Mauricio Esteban. 2011. Actualización de la geología de superficie en la Sierra de Perijá mediante la utilización de imágenes satelitales, 1–125. Simón Bolívar University. Accessed 2017-08-03.

Maps

• Colmenares, Fabio; Milena Mesa; Jairo Roncancio; Edgar Arciniegas; Pablo Pedraza; Agustín Cardona; César Silva; Jhoamna Romero, and Sonia Alvarado and Oscar Romero, Felipe Vargas, Carlos Santamaría. 2007. Plancha 34 - Agustín Codazzi - 1:100,000, 1. INGEOMINAS. Accessed 2017-06-14.
• Hernández, Marina, and Jairo Clavijo. 2008. Plancha 48 - La Jagua de Ibirico - 1:100,000, 1. INGEOMINAS. Accessed 2017-06-14.