The Cancañiri Formation, also named as Cancañiri Tillite, is a
Katian
The Katian is the second stage of the Upper Ordovician. It is preceded by the Sandbian and succeeded by the Hirnantian Stage. The Katian began million years ago and lasted for about 7.6 million years until the beginning of the Hirnantian mill ...
to
Hirnantian
The Hirnantian is the final internationally recognized stage of the Ordovician Period of the Paleozoic Era. It was of short duration, lasting about 2.1 million years, from to Ma (million years ago). The early part of the Hirnantian was char ...
geologic
formation of central Bolivia. The pebbly,
argillaceous
Clay minerals are hydrous aluminium phyllosilicates (e.g. kaolin, Al2 Si2 O5( OH)4), sometimes with variable amounts of iron, magnesium, alkali metals, alkaline earths, and other cations found on or near some planetary surfaces.
Clay mineral ...
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,
shale
Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of Clay mineral, clay minerals (hydrous aluminium phyllosilicates, e.g., Kaolinite, kaolin, aluminium, Al2Silicon, Si2Oxygen, O5(hydroxide, OH)4) and tiny f ...
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.
Although its permeabil ...
s of the up to thick formation,
[Díaz Martínez, 2005, p.237] were deposited in a
glacial
A glacier (; or ) is a persistent body of dense ice, a form of rock, that is constantly moving downhill under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires ...
foreshore to deep water
turbiditic
A turbidity current is most typically an underwater current of usually rapidly moving, sediment-laden water moving down a slope; although current research (2018) indicates that water-saturated sediment may be the primary actor in the process. ...
environment.
[Díaz Martínez, 1997, p.55] The formation is named after Cancañiri, a mining town close to
Llallagua, where a local legend of a possessed woman is believed.
The formation overlies the
San Benito Formation in Cochabamba and the
Amutara Formation in other parts. The Cancañiri Formation is overlain by the
Uncía Formation.
[Díaz Martínez, 1997, p.56]
Fossil content
The formation has provided the following fossils:
* ''
Destombesium pacochicoensis''
* ''
Dinorthis flabellulum''
* ''
Drabovinella curiosa''
* ''
Tunariorthis cardocanalis''
* ''
Oanduporella sp.''
* ''
Rostricellula sp.''
See also
*
List of fossiliferous stratigraphic units in Bolivia
This is a list of fossiliferous stratigraphic units in Bolivia.
__NOTOC__
List of fossiliferous stratigraphic units
See also
*
* Gomphothere fossils in Bolivia
* South American land mammal ages
* List of fossiliferous stratigraphic units ...
References
Bibliography
*
*
Further reading
* V. Havlicek and L. Branisa. 1980. Ordovician brachiopods of Bolivia: Succession of assemblages, climate control, affinity to Anglo-French and Bohemian provinces. Rozpravy Ceskoslovenske Akademie Ved. Rada Matematickych a Prirodnich Ved. Academia Praha, Prague, Czechoslovakia 90(1):1-54
{{DEFAULTSORT:Cacaniri Formation
Geologic formations of Bolivia
Ordovician System of South America
Silurian System of South America
Ordovician Bolivia
Silurian Bolivia
Katian
Hirnantian
Sandstone formations
Shale formations
Siltstone formations
Glacial deposits
Deep marine deposits
Turbidite deposits
Ordovician southern paleotemperate deposits
Silurian southern paleotemperate deposits
Paleontology in Bolivia
Geology of Cochabamba Department
Geology of Potosí Department