Río Cachirí Group

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.

Río Cachirí Group
Stratigraphic range: Devonian 419–360 Ma PreꞒ Ꞓ 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	10°50′03″N 72°14′23″W
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

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.^[1]

Description

Lithologies

The group contains black, grey and red shales, grey micaceous sandstones, quartzitic sandstones and red and bluish grey limestones.^[1]

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).^[1] The group is recognised along a section of approximately 110 kilometres (68 mi) in the Venezuelan terrain.^[2] 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.^[3] The sediments of the Río Cachirí Group were deposited in an epicontinental sea at the edge of the Paleo-Tethys Ocean.^[1]

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.^[4]

Outcrops

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.^[5][6]

Regional correlations

Stratigraphy of the Llanos Basin and surrounding provinces

Ma	Age	Paleomap	Regional events	Catatumbo	Cordillera	proximal Llanos	distal Llanos	Putumayo	VSM	Environments	Maximum thickness	Petroleum geology	Notes
0.01	Holocene		Holocene volcanism Seismic activity	alluvium								Overburden
1	Pleistocene		Pleistocene volcanism Andean orogeny 3 Glaciations	Guayabo	Soatá Sabana	Necesidad	Guayabo	Gigante Neiva		Alluvial to fluvial (Guayabo)	550 m (1,800 ft) (Guayabo)		[7][8][9][10]
2.6	Pliocene		Pliocene volcanism Andean orogeny 3 GABI		Subachoque
5.3	Messinian		Andean orogeny 3 Foreland		Marichuela			Caimán	Honda				[9][11]
13.5	Langhian		Regional flooding	León	hiatus	Caja	León			Lacustrine (León)	400 m (1,300 ft) (León)	Seal	[10][12]
16.2	Burdigalian		Miocene inundations Andean orogeny 2	C1		Carbonera C1		Ospina		Proximal fluvio-deltaic (C1)	850 m (2,790 ft) (Carbonera)	Reservoir	[11][10]
17.3				C2		Carbonera C2				Distal lacustrine-deltaic (C2)		Seal
19				C3		Carbonera C3				Proximal fluvio-deltaic (C3)		Reservoir
21	Early Miocene		Pebas wetlands	C4		Carbonera C4			Barzalosa	Distal fluvio-deltaic (C4)		Seal
23	Late Oligocene		Andean orogeny 1 Foredeep	C5		Carbonera C5		Orito		Proximal fluvio-deltaic (C5)		Reservoir	[8][11]
25				C6		Carbonera C6				Distal fluvio-lacustrine (C6)		Seal
28	Early Oligocene			C7		C7		Pepino	Gualanday	Proximal deltaic-marine (C7)		Reservoir	[8][11][13]
32	Oligo-Eocene			C8	Usme	C8	onlap			Marine-deltaic (C8)		Seal Source	[13]
35	Late Eocene			Mirador		Mirador				Coastal (Mirador)	240 m (790 ft) (Mirador)	Reservoir	[10][14]
40	Middle Eocene				Regadera				hiatus
45
50	Early Eocene			Socha		Los Cuervos				Deltaic (Los Cuervos)	260 m (850 ft) (Los Cuervos)	Seal Source	[10][14]
55	Late Paleocene		PETM 2000 ppm CO2	Los Cuervos	Bogotá				Gualanday
60	Early Paleocene		SALMA	Barco	Guaduas	Barco		Rumiyaco		Fluvial (Barco)	225 m (738 ft) (Barco)	Reservoir	[7][8][11][10][15]
65	Maastrichtian		KT extinction	Catatumbo	Guadalupe				Monserrate	Deltaic-fluvial (Guadalupe)	750 m (2,460 ft) (Guadalupe)	Reservoir	[7][10]
72	Campanian		End of rifting	Colón-Mito Juan									[10][16]
83	Santonian							Villeta/Güagüaquí
86	Coniacian
89	Turonian		Cenomanian-Turonian anoxic event	La Luna	Chipaque	Gachetá	hiatus			Restricted marine (all)	500 m (1,600 ft) (Gachetá)	Source	[7][10][17]
93	Cenomanian		Rift 2
100	Albian				Une	Une		Caballos		Deltaic (Une)	500 m (1,600 ft) (Une)	Reservoir	[11][17]
113	Aptian			Capacho	Fómeque			Motema	Yaví	Open marine (Fómeque)	800 m (2,600 ft) (Fómeque)	Source (Fóm)	[8][10][18]
125	Barremian		High biodiversity	Aguardiente	Paja					Shallow to open marine (Paja)	940 m (3,080 ft) (Paja)	Reservoir	[7]
129	Hauterivian		Rift 1	Tibú- Mercedes	Las Juntas	hiatus				Deltaic (Las Juntas)	910 m (2,990 ft) (Las Juntas)	Reservoir (LJun)	[7]
133	Valanginian			Río Negro	Cáqueza Macanal Rosablanca					Restricted marine (Macanal)	2,935 m (9,629 ft) (Macanal)	Source (Mac)	[8][19]
140	Berriasian			Girón
145	Tithonian		Break-up of Pangea	Jordán	Arcabuco	Buenavista Batá		Saldaña		Alluvial, fluvial (Buenavista)	110 m (360 ft) (Buenavista)	"Jurassic"	[11][20]
150	Early-Mid Jurassic		Passive margin 2	La Quinta	Montebel Noreán	hiatus				Coastal tuff (La Quinta)	100 m (330 ft) (La Quinta)		[21]
201	Late Triassic			Mucuchachi				Payandé					[11]
235	Early Triassic		Pangea		hiatus							"Paleozoic"
250	Permian
300	Late Carboniferous		Famatinian orogeny						Cerro Neiva ()				[22]
340	Early Carboniferous		Fossil fish Romer's gap		Cuche (355-385)	Farallones ()				Deltaic, estuarine (Cuche)	900 m (3,000 ft) (Cuche)
360	Late Devonian		Passive margin 1	Río Cachirí (360-419)					Ambicá ()	Alluvial-fluvial-reef (Farallones)	2,400 m (7,900 ft) (Farallones)		[19][23][24][25][26]
390	Early Devonian		High biodiversity	Floresta (387-400) El Tíbet						Shallow marine (Floresta)	600 m (2,000 ft) (Floresta)
410	Late Silurian		Silurian mystery
425	Early Silurian			hiatus
440	Late Ordovician		Rich fauna in Bolivia	San Pedro (450-490)		Duda ()
470	Early Ordovician		First fossils		Busbanzá (>470±22) Chuscales Otengá	Guape ()		Río Nevado ()	Hígado () Agua Blanca Venado (470-475)				[27][28][29]
488	Late Cambrian		Regional intrusions	Chicamocha (490-515)	Quetame ()	Ariarí ()		SJ del Guaviare (490-590)	San Isidro ()				[30][31]
515	Early Cambrian		Cambrian explosion										[29][32]
542	Ediacaran		Break-up of Rodinia		pre-Quetame		post-Parguaza		El Barro ()	Yellow: allochthonous basement (Chibcha terrane) Green: autochthonous basement (Río Negro-Juruena Province)		Basement	[33][34]
600	Neoproterozoic		Cariri Velhos orogeny	Bucaramanga (600-1400)				pre-Guaviare					[30]
800			Snowball Earth										[35]
1000	Mesoproterozoic		Sunsás orogeny			Ariarí (1000)			La Urraca (1030-1100)				[36][37][38][39]
1300			Rondônia-Juruá orogeny			pre-Ariarí	Parguaza (1300-1400)		Garzón (1180-1550)				[40]
1400				pre-Bucaramanga									[41]
1600	Paleoproterozoic						Maimachi (1500-1700)		pre-Garzón				[42]
1800			Tapajós orogeny				Mitú (1800)						[40][42]
1950			Transamazonic orogeny				pre-Mitú						[40]
2200			Columbia
2530	Archean		Carajas-Imataca orogeny										[40]
3100			Kenorland
Sources

Legend

• group
• important formation
• fossiliferous formation
• minor formation
• (age in Ma)
• proximal Llanos (Medina)^{[note 1]}
• distal Llanos (Saltarin 1A well)^{[note 2]}

See also

• Colombia portal
• Geology portal
• Venezuela portal

Geology of the Eastern Hills

Geology of the Ocetá Páramo

Geology of the Altiplano Cundiboyacense

Notes

1. based on Duarte et al. (2019)^[43], García González et al. (2009),^[44] and geological report of Villavicencio^[45]
2. based on Duarte et al. (2019)^[43] and the hydrocarbon potential evaluation performed by the UIS and ANH in 2009^[46]