The Barzalosa Formation ( es, Formación Barzalosa, Pgb, Pgba) is a fossiliferous geological formation of the Upper Magdalena Valley and the bounding foothills of the

Central Ranges Central Ranges (code CER) is an Australian bioregion, with an area of 101,640.44 square kilometres (39,244 sq mi) spreading across two states and one territory: South Australia, Western Australia, and the Northern Territory.Eastern Ranges of the

Colombia Colombia (, ; ), officially the Republic of Colombia, is a country in South America with insular regions in North America—near Nicaragua's Caribbean coast—as well as in the Pacific Ocean. The Colombian mainland is bordered by the Car ...

n Andes. The formation consists of

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s, sandstones and

siltstone Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility.Blatt ''et al.'' 1980, p ...

s. The Barzalosa Formation probably dates to the Late Paleogene to Early Neogene period;

Oligocene The Oligocene ( ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but the ...

to Early Miocene epochs, and has an approximate thickness of . Fossils of '' Balanerodus logimus'', '' Lophiodolodus chaparralensis'', '' Xenastrapotherium chaparralensis'', '' Protheosodon sp.'' and '' Proadinotherium sp.'' have been uncovered from the formation in

Chaparral Chaparral ( ) is a shrubland plant community and geographical feature found primarily in the U.S. state of California, in southern Oregon, and in the northern portion of the Baja California Peninsula in Mexico. It is shaped by a Mediterranean c ...

, Tolima.

Etymology

The formation was defined by Scheibe in 1934 and named after Barzalosa, a ''vereda'' of Girardot, Cundinamarca. Cáceres and Etayo elevated the "Pisos de Barzalosa" to a formation in 1969.Acosta et al., 2002, p.49

Description

Lithologies

The Barzalosa Formation consists of

s, sandstones and

s.Acosta et al., 2002, p.50 In parts, the formation contains

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especial ...

beds and gypsum.Acosta & Ulloa, 2001, p.56

Stratigraphy and depositional environment

The approximately thick Barzalosa Formation overlies the Olini Group and the Seca Formation in the west and is overlain by the

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. In the east towards Fusagasugá, the formation overlies the La Tabla Formation and is overlain by the Carmen de Apicalá Conglomerate.Acosta & Ulloa, 2001, p.52 As the formation does not contain foraminifera, the age is difficult to establish, but has been estimated to be

to Early Miocene, or Middle Eocene to Oligocene.Acosta & Ulloa, 2001, p.57 The depositional environment has been interpreted as alluvial fans and

braided river A braided river, or braided channel, consists of a network of river channels separated by small, often temporary, islands called braid bars or, in English usage, ''aits'' or ''eyots''. Braided streams tend to occur in rivers with high sediment l ...

s.Acosta et al., 2002, p.51

Fossil content

Outcrops

The Barzalosa Formation is apart from its type locality found in

Tocaima Tocaima () refers to both a city and a municipality in Cundinamarca, Colombia. City The city of Tocaima was founded on March 20, 1544 as San Dionisio de los Caballeros de Tocaima by the Spanish explorer Hernán Venegas Carrillo. This small city ...

and to the east of Agua de Dios, and on the western side of the Magdalena River around

, Tolima.

Regional correlations

Notes

References

Bibliography

* *

Maps

* * {{Paleontology in Colombia, state=collapsed Geologic formations of Colombia Paleogene Colombia Neogene Colombia Oligocene Series of South America Miocene Series of South America Conglomerate formations Sandstone formations Siltstone formations Alluvial deposits Fluvial deposits Fossiliferous stratigraphic units of South America Paleontology in Colombia Formations Formations