The Santa Teresa Formation (, Tist, Pgst) 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 expo ...

of the western

Eastern Ranges The Eastern Ranges is an Australian rules football team that currently competes in the Talent League, the Victorian statewide under-18s competition. History Inaugural playing squad (1992) Honours *Premiers (2): 2002, 2013 *Runners-up (6): 199 ...

of the

Colombia Colombia, officially the Republic of Colombia, is a country primarily located in South America with Insular region of Colombia, insular regions in North America. The Colombian mainland is bordered by the Caribbean Sea to the north, Venezuel ...

Andes The Andes ( ), Andes Mountains or Andean Mountain Range (; ) are the List of longest mountain chains on Earth, longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range ...

, west of the

Bituima Fault Bituima is a municipality and town of Colombia Colombia, officially the Republic of Colombia, is a country primarily located in South America with Insular region of Colombia, insular regions in North America. The Colombian mainland is bor ...

, and the southern

Middle Magdalena Valley The Middle Magdalena Valley, Middle Magdalena Basin or Middle Magdalena Valley Basin (, commonly abbreviated to VMM) is an intermontane basin, located in north-central Colombia between the Central and Eastern Ranges of the Andes. The basin, cove ...

. The formation spreads across the western part of Cundinamarca and the northern portion of Tolima. The formation consists of grey claystones intercalated by orange

quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The Atom, atoms are linked in a continuous framework of SiO4 silicon–oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tet ...

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. Although its permeabil ...

s and

sandstone Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...

s of small to conglomeratic

grain size Grain size (or particle size) is the diameter of individual grains of sediment, or the lithified particles in clastic rocks. The term may also be applied to other granular materials. This is different from the crystallite size, which ...

. The thickness at its type section has been measured to be and a maximum thickness of suggested. In the formation, dated on the basis of its fossil content to the

Late Oligocene The Chattian is, in the geologic timescale The geologic time scale or geological time scale (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the pro ...

, many leaf imprints and mollusks were found, suggesting a

lacustrine A lake is often a naturally occurring, relatively large and fixed body of water on or near the Earth's surface. It is localized in a basin or interconnected basins surrounded by dry land. Lakes lie completely on land and are separate from t ...

to deltaic

depositional environment In geology, depositional environment or sedimentary environment describes the combination of physical, chemical, and biological processes associated with the deposition of a particular type of sediment and, therefore, the rock types that will b ...

with periodical marine incursions.

Etymology

The formation was defined by De Porta in 1966 and named after the vereda Santa Teresa,

San Juan de Rioseco San Juan de Rioseco is a municipality and town of Colombia in the department of Cundinamarca with a population of about 10,000 people. It lies in mountainous terrain in the coffee land at an altitude of about 4,000 feet, high above the Magdalena ...

.Acosta & Ulloa, 2001, p.64

Description

The Santa Teresa Formation is the youngest unit outcropping in the Jerusalén-

Guaduas Guaduas () is a municipality and town in Colombia, in the Lower Magdalena Province department of Cundinamarca Department, Cundinamarca, about 117 km from Bogotá. It is an agricultural and tourist center of some importance with a populati ...

synclinal Synclinal may refer to: * Syncline, in structural geology, a syncline is a fold, with younger layers closer to the center of the structure. *Synclinal, in alkane stereochemistry, a torsion angle between 30° to 90° and –30° to –90° See als ...

, western

, covering the San Juan de Río Seco Formation. The formation was formerly called La Cira Formation. In the Balú quebrada, the formation shows a thickness of , while the maximum thickness could reach . The lower boundary of the formation is marked by the first occurrence of grey

claystone Mudrocks are a class of fine-grained siliciclastic sedimentary rocks. The varying types of mudrocks include siltstone, claystone, mudstone and shale. Most of the particles of which the stone is composed are less than and are too small to ...

s, covering the light brown claystones of the San Juan de Río Seco Formation. The formation comprises grey claystones intercalated by orange

s and

s of small to conglomeratic

. The

roundness Roundness is the measure of how closely the shape of an object approaches that of a mathematically perfect circle. Roundness applies in two dimensions, such as the cross sectional circles along a cylindrical object such as a shaft or a cylindr ...

of the sandstone grains has been characterized as angular to subangular by Lamus Ochoa et al. in 2013. The claystones occur in thick layers with wavy lamination. In these thick packages of claystones, the formation has provided fossil leaves in various forms and sizes, and to a lesser extent the remains of

mollusk Mollusca is a phylum of protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant species of molluscs are recognized, making it the second-largest animal phylum after Arthropoda. The ...

gastropod Gastropods (), commonly known as slugs and snails, belong to a large Taxonomy (biology), taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, freshwater, and fro ...

s and

bivalve Bivalvia () or bivalves, in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class (biology), class of aquatic animal, aquatic molluscs (marine and freshwater) that have laterally compressed soft bodies enclosed b ...

s. The basal contacts of these beds are straight to transitional and most of the time are coarsening upward towards

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 sil ...

s where the gastropods dominate. These

facies In geology, a facies ( , ; same pronunciation and spelling in the plural) is a body of rock with distinctive characteristics. The characteristics can be any observable attribute of rocks (such as their overall appearance, composition, or con ...

sequences have a thickness of about . Locally,

bioturbation Bioturbation is defined as the reworking of soils and sediments by animals or plants. It includes burrowing, ingestion, and defecation of sediment grains. Bioturbating activities have a profound effect on the environment and are thought to be a ...

siderite Siderite is a mineral composed of iron(II) carbonate (FeCO3). Its name comes from the Ancient Greek word (), meaning "iron". A valuable iron ore, it consists of 48% iron and lacks sulfur and phosphorus. Zinc, magnesium, and manganese commonly ...

nodules 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 Chemical element, elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. Coal i ...

beds occur in the formation. The sandstones occur in very thin to very thick beds, characterized by plain parallel lamination, in lenses and very locally in flasers. The cement of the arenites is

calcareous Calcareous () is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime (mineral), lime or being chalky. The term is used in a wide variety of Science, scientific disciplines. In zoology ''Calcare ...

. The grain composition of the lithic fraction comprises

zircon Zircon () is a mineral belonging to the group of nesosilicates and is a source of the metal zirconium. Its chemical name is zirconium(IV) silicate, and its corresponding chemical formula is Zr SiO4. An empirical formula showing some of th ...

epidote Epidote is a calcium aluminium iron sorosilicate mineral. Description Well developed crystals of epidote, Ca2Al2(Fe3+;Al)(SiO4)(Si2O7)O(OH), crystallizing in the monoclinic system, are of frequent occurrence: they are commonly prismatic in ha ...

zoisite Zoisite, first known as saualpite, after its type locality, is a calcium aluminum hydroxy sorosilicate belonging to the epidote group of minerals. Its chemical formula is Ca2 Al3( Si O4)(Si2O7)O(O H). Zoisite occurs as prismatic, orthorho ...

clinozoisite Clinozoisite is a complex calcium aluminium sorosilicate mineral with formula: Ca2Al3(Si2O7)(SiO4)O(OH). It forms a continuous solid solution series with epidote by substitution of iron(III) in the aluminium (m3 site) and is also called ''aluminiu ...

and

pyroxene The pyroxenes (commonly abbreviated Px) are a group of important rock-forming inosilicate minerals found in many igneous and metamorphic rocks. Pyroxenes have the general formula , where X represents ions of calcium (Ca), sodium (Na), iron ( ...

s, which at the top of the formation amounts to 86 percent.

Stratigraphy and depositional environment

The Santa Teresa Formation conformably overlies the San Juan de Río Seco Formation and is covered by subrecent

alluvium Alluvium (, ) is loose clay, silt, sand, or gravel that has been deposited by running water in a stream bed, on a floodplain, in an alluvial fan or beach, or in similar settings. Alluvium is also sometimes called alluvial deposit. Alluvium is ...

. The formation is part of the sequence after the

Eocene The Eocene ( ) is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes ...

unconformity An unconformity is a buried erosional or non-depositional surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval ...

. The age has been inferred to be

. The

has been interpreted as

with marine influence in the form of channels. The abundance of

brackish Brackish water, sometimes termed brack water, is water occurring in a natural environment that has more salinity than freshwater, but not as much as seawater. It may result from mixing seawater (salt water) and fresh water together, as in estuari ...

and fresh water gastropods suggests these environmental conditions prevailed in the Oligocene of central Colombia. In the type section at the Balú quebrada, facies traits that confirm this interpretation can be observed. The lacustrine areas were probably shallow water environments with reducing conditions and a continuous supply of

siliciclastic Siliciclastic (or ''siliclastic'') rocks are clastic noncarbonate sedimentary rocks that are composed primarily of silicate minerals, such as quartz or clay minerals. Siliciclastic rock types include mudrock, sandstone Sandstone is a Clastic ...

s by small

deltas A river delta is a landform, wikt:archetype#Noun, archetypically triangular, created by the deposition (geology), deposition of the sediments that are carried by the waters of a river, where the river merges with a body of slow-moving water or ...

. The many leaf imprints and coal layers support the presence of a lush vegetation at the time of deposition. The abundance of lithic clasts near the top of the formation supports a renewed

provenance Provenance () is the chronology of the ownership, custody or location of a historical object. The term was originally mostly used in relation to works of art, but is now used in similar senses in a wide range of fields, including archaeology, p ...

area to the east; the uplift of the Eastern Ranges of the Colombian Andes, due to activity of the La Salina Fault.Caballero et al., 2010, p.74

Paleontology

The Santa Teresa Formation has provided fossil

s, described by De Porta and Solé De Porta in 1962 and De Porta '' Anodontites laciranus'', '' Diplodon oponcintonis'', '' Diplodon waringi'',Acosta Garay et al., 2002, p.49 and '' Corbula sp.'', among other mollusks described by De Porta in 1966.

Regional correlations

Notes and references

Notes

References

Bibliography

''See also sources for the correlation table'' * * * *

Maps

* * * * {{citation , last=Acosta , first=Jorge E. , last2=Guatame , first2=Rafael , last3=Torres , first3=Oscar , last4=Solano , first4=Frank , year=1999 , title=Plancha 245 - Girardot - 1:100,000 , url=https://drive.google.com/open?id=0BwFQPMJEi17QUmhEQTdMNmcxT28 , publisher=

INGEOMINAS The Colombian Geological Survey (CGS) (; 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 in basic and applied geosciences ...

, pages=1 , accessdate=2017-06-06 Geologic formations of Colombia Paleogene Colombia Oligocene Series of South America Deseadan Chattian Stage Shale formations Sandstone formations Siltstone formations Coal formations Deltaic deposits Lacustrine deposits Fossiliferous stratigraphic units of South America Formations Formations