The Caballos Formation ( es, Formación Caballos, KI) is a

geological formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exp ...

of the

Upper Magdalena Valley Upper may refer to: * Shoe upper or ''vamp'', the part of a shoe on the top of the foot * Stimulant, drugs which induce temporary improvements in either mental or physical function or both * ''Upper'', the original film title for the 2013 found fo ...

(VSM), Caguán-Putumayo Basin,

Central Central is an adjective usually referring to being in the center of some place or (mathematical) object. Central may also refer to: Directions and generalised locations * Central Africa, a region in the centre of Africa continent, also known as ...

and

Eastern Ranges The Eastern Ranges is an Australian rules football team in the NAB League, the Victorian statewide under-18s competition. The club is a founding member of the competition (1992) and has produced several players for the Australian Football Leagu ...

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 ...

Andes The Andes, Andes Mountains or Andean Mountains (; ) are the longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range is long, wide (widest between 18°S – 20°S ...

. The

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates) ...

and

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 ...

formation dates to the

Middle Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...

period;

Aptian The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous Epoch or Series and encompasses the time from 121.4 ± 1.0 Ma to 113.0 ± 1.0 Ma (million years ago), a ...

Albian The Albian is both an age of the geologic timescale and a stage in the stratigraphic column. It is the youngest or uppermost subdivision of the Early/Lower Cretaceous Epoch/Series. Its approximate time range is 113.0 ± 1.0 Ma to 100.5 ± 0.9 M ...

epochs and has a maximum thickness of .

Etymology

The formation was defined and named in 1967 by Corrigan after Cerro Caballos, to the west of Olaya Herrera, Tolima.Velandia et al., 2001, p.53

Description

Lithologies

The Caballos Formation has a maximum thickness of in the Quebrada Bambucá and is characterized by a lower sequence of fine to coarse

s, of lithic arenite,

quartz arenite A quartz arenite or quartzarenite is a sandstone composed of greater than 90% detrital quartz. Quartz arenites are the most mature sedimentary rocks possible, and are often referred to as ultra- or super-mature, and are usually cemented by sili ...

and

feldspar Feldspars are a group of rock-forming aluminium tectosilicate minerals, also containing other cations such as sodium, calcium, potassium, or barium. The most common members of the feldspar group are the ''plagioclase'' (sodium-calcium) feldsp ...

arenite Arenite (Latin: ''arena'', "sand") is a sedimentary clastic rock with sand grain size between 0.0625 mm (0.00246 in) and 2 mm (0.08 in) and contain less than 15% matrix. The related adjective is ''arenaceous''. The equivalent ...

composition, a middle section of fossiliferous

black 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, especiall ...

s 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, intercalated by micritic

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...

s and

coal Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. Coal is formed when dea ...

s and very fine sandstones. The upper part of the formation contains conglomerates and

glauconitic Glauconite is an iron potassium phyllosilicate (mica group) mineral of characteristic green color which is very friable and has very low weathering resistance. It crystallizes with a monoclinic geometry. Its name is derived from the Greek () me ...

sandstones.

Stratigraphy and depositional environment

The Caballos Formation in some parts concordantly overlies the Yaví Formation and in other parts rests unconformably on the Saldaña Formation and Ibagué Batholith.Velandia et al., 2001, p.34 The formation is overlain by the

Hondita Formation The Hondita Formation ( es, Formación Hondita, Ksh) is a fossiliferous geological formation of the Upper Magdalena Valley (VSM) and surrounding Central and Eastern Ranges of the Colombian Andes, extending from Cundinamarca in the north to Huila ...

. The age has been estimated to be

. Stratigraphically, the formation is time equivalent with the

Une Une is a municipality and town of Colombia in the Eastern Province, Cundinamarca, Eastern Province, part of the Departments of Colombia, department of Cundinamarca Department, Cundinamarca. The urban centre is located at an altitude of at a dista ...

Aguardiente (Spanish), or (Portuguese) ( eu, pattar; ca, aiguardent; gl, augardente), is a generic term for alcoholic beverages that contain between 29% and 60% alcohol by volume (ABV). It originates in the Iberian Peninsula (Portugal and Spain) and in I ...

Simijaca Simijaca () is a town and municipality in the Ubaté Province, part of the Cundinamarca Department, Colombia. The town centre is located at an altitude of on the Altiplano Cundiboyacense at from the capital Bogotá. Simijaca borders the Boyacá D ...

, El Peñón, Capotes, Tablazo, Tibú-Mercedes and Pacho Formations.Velandia et al., 2001, p.54 The formation has been deposited in a

fluvial In geography and geology, fluvial processes are associated with rivers and streams and the deposits and landforms created by them. When the stream or rivers are associated with glaciers, ice sheets, or ice caps, the term glaciofluvial or fluviog ...

estuarine An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environment ...

and

shallow marine Shallow water marine environment refers to the area between the shore and deeper water, such as a reef wall or a shelf break. This environment is characterized by oceanic, geological and biological conditions, as described below. The water in this ...

environment Environment most often refers to: __NOTOC__ * Natural environment, all living and non-living things occurring naturally * Biophysical environment, the physical and biological factors along with their chemical interactions that affect an organism or ...

. The Caballos Formation is a

source Source may refer to: Research * Historical document * Historical source * Source (intelligence) or sub source, typically a confidential provider of non open-source intelligence * Source (journalism), a person, publication, publishing institute o ...

reservoir A reservoir (; from French ''réservoir'' ) is an enlarged lake behind a dam. Such a dam may be either artificial, built to store fresh water or it may be a natural formation. Reservoirs can be created in a number of ways, including contro ...

and

seal rock A petroleum reservoir or oil and gas reservoir is a subsurface accumulation of hydrocarbons contained in porous or fractured rock formations. Such reservoirs form when kerogen (ancient plant matter) is created in surrounding rock by the presence ...

in the

, and a source and reservoir rock in the Caguán-Putumayo Basin. The Orito and Moqueta Fields of the latter basin produce from Caballos reservoirs.

Fossil content

The formation has provided fossils of '' Heminautilus etheringtoni'', '' Araucarites sp.'', '' Brachyphyllum sp.'', '' Cladophlebis sp.'', and '' Weichselia sp.'', as well as many types of

pollen Pollen is a powdery substance produced by seed plants. It consists of pollen grains (highly reduced microgametophytes), which produce male gametes (sperm cells). Pollen grains have a hard coat made of sporopollenin that protects the gametophyt ...

.Los Mangos
at

Fossilworks Fossilworks is a portal which provides query, download, and analysis tools to facilitate access to the Paleobiology Database The Paleobiology Database is an online resource for information on the distribution and classification of fossil animals ...

.org

Outcrops

The Caballos Formation is apart from its type locality, found in Huila, Tolima and Putumayo Departments.

Regional correlations

Notes

References

Bibliography

* * * * * * *

Maps

* * * * * * * * * * * * * * * * * * * * * * * * {{cite LSA , last=Núñez , first=Alberto , last2=Gómez , first2=Jorge , year=2002 , title=Plancha 465 - Churiyaco - 1:100,000 , url=https://drive.google.com/open?id=0BwFQPMJEi17QdC0zUmFoZnl1cmc , publisher=

INGEOMINAS The Colombian Geological Survey (CGS) ( es, Servicio Geológico Colombiano; formerly known as INGEOMINAS) is a scientific agency of the Colombian government in charge of contributing to the socioeconomic development of the nation through research ...

, pages=1 , accessdate=2017-06-06 Geologic formations of Colombia Cretaceous Colombia Lower Cretaceous Series of South America Albian Stage Aptian Stage Sandstone formations Shale formations Siltstone formations Limestone formations Coal formations Fluvial deposits Shallow marine deposits Source rock formations Reservoir rock formations Seal rock formations Fossiliferous stratigraphic units of South America Paleontology in Colombia Formations Formations Formations