Estratos de Pupunahue is the name given to the sedimentary strata of Oligocene-Miocene age that crop out in
Pupunahue Pupunahue is a coal mine and hamlet in Los Ríos Region near the towns of Máfil and Los Lagos. The coal beds exploited in Pupunahue belong to the Pupunahue Beds. Geologically the sedimentary rocks of the Pupunahue Beds containing coal lie in Pupu ...
Valdivia
Valdivia (; Mapuche: Ainil) is a city and commune in southern Chile, administered by the Municipality of Valdivia. The city is named after its founder, Pedro de Valdivia, and is located at the confluence of the Calle-Calle, Valdivia, and ...
,
Chile
Chile, officially the Republic of Chile, is a country in western South America. It is the southernmost country in the world and the closest to Antarctica, stretching along a narrow strip of land between the Andes, Andes Mountains and the Paci ...
. Outside this locality Estratos de Pupunahue extends below the surface over a larger area. The thickness of the strata varies from a few meters to 530 meters. The strata were initially described by
Henning Illies
Jürgen Henning Illies (14 March 1924 – 2 August 1982) was a German geologist, an expert in taphrogenesis (rift formation). Apart from his work on rifts, including the Rhine Rift Valley, he is known for his contributions to Chilean geology.
...
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 ...
and
mudstone
Mudstone, a type of mudrock, is a fine-grained sedimentary rock whose original constituents were clays or muds. Mudstone is distinguished from ''shale'' by its lack of fissility.Blatt, H., and R.J. Tracy, 1996, ''Petrology.'' New York, New York, ...
(
Chilean Spanish
Chilean Spanish ( or ) is any of several varieties of the Spanish language spoken in most of Chile. Chilean Spanish dialects have distinctive pronunciation, grammar, vocabulary, and slang usages that differ from those of Standard Spanish, with ...
: ''fangolita''). The clast of the conglomerates are made up of
metamorphic rock
Metamorphic rocks arise from the transformation of existing rock to new types of rock in a process called metamorphism. The original rock ( protolith) is subjected to temperatures greater than and, often, elevated pressure of or more, caus ...
and the disposition of the conglomerates varies from clast-supported to matrix-supported. The sandstone and mudstone contain layers of
lignite coal
Lignite (derived from Latin ''lignum'' meaning 'wood'), often referred to as brown coal, is a soft, brown, combustible sedimentary rock formed from naturally compressed peat. It has a carbon content around 25–35% and is considered the lowest ...
that exceed 30 cm in thickness.
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 ...
layers found in the Estratos de Pupunahue have been exploited in the mines of
Catamutún
Catamutún is a coal mine and locality in Los Ríos Region, Chile.Pupunahue Pupunahue is a coal mine and hamlet in Los Ríos Region near the towns of Máfil and Los Lagos. The coal beds exploited in Pupunahue belong to the Pupunahue Beds. Geologically the sedimentary rocks of the Pupunahue Beds containing coal lie in Pupu ...
and Mulpún ("Mulpun Beds").
The strata are very similar to the
Cheuquemó Formation
Cheuquemó Formation () is a geological formation of sedimentary rock in south-central Chile. The sediments of the formation were deposited during the Late Oligocene and Early Miocene epochs. The formations lower sections are made up of conglome ...
found further north, with the sole difference that the fossil assemblage in both seems to indicate different ages. While Cheuquemó Formation is possibly about 14 million years old (Miocene), Estratos de Pupunahue are 35–25 million years old.