Río Cachirí Group

The Río Cachirí Group (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 2438 m. 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.

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 2438 m, while the thickness on the Colombian side of the range does not exceed 1100 m. The group is recognised along a section of approximately 110 km 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
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.