Tobífera Formation ( es, Formación Tobífera) is a volcano-sedimentary

formation Formation may refer to: Linguistics * Back-formation, the process of creating a new lexeme by removing or affixes * Word formation, the creation of a new word by adding affixes Mathematics and science * Cave formation or speleothem, a secondary ...

Middle Middle or The Middle may refer to: * Centre (geometry), the point equally distant from the outer limits. Places * Middle (sheading), a subdivision of the Isle of Man * Middle Bay (disambiguation) * Middle Brook (disambiguation) * Middle Creek (d ...

Late Jurassic The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 163.5 ± 1.0 to 145.0 ± 0.8 million years ago (Ma), which is preserved in Upper Jurassic strata.Owen 1987. In European lithostratigraphy, the ...

age. The formation is crops out in the

Magallanes Region The Magallanes Region (), officially the Magallanes y la Antártica Chilena Region ( es, Región de Magallanes y de la Antártica Chilena), is one of Chile's 16 first order administrative divisions. It is the southernmost, largest, and second lea ...

in southern

Patagonia Patagonia () refers to a geographical region that encompasses the southern end of South America, governed by Argentina and Chile. The region comprises the southern section of the Andes Mountains with lakes, fjords, temperate rainforests, and ...

and

Tierra del Fuego Tierra del Fuego (, ; Spanish for "Land of the Fire", rarely also Fireland in English) is an archipelago off the southernmost tip of the South American mainland, across the Strait of Magellan. The archipelago consists of the main island, Isla ...

of Chile, the

Santa Cruz Province Santa Claus, also known as Father Christmas, Saint Nicholas, Saint Nick, Kris Kringle, or simply Santa, is a legendary figure originating in Western Christian culture who is said to bring children gifts during the late evening and overnigh ...

of southern Argentina, and in the subsurface of the

Malvinas Basin The Malvinas Basin ( es, Cuenca de Malvinas) is a major sedimentary basin in the Argentine Shelf offshore southern Patagonia. The basin borders to the west with the Río Chico-Dungeness High that separates it from the Magallanes Basin.Gallardo ...

offshore Argentina and the

Falkland Islands The Falkland Islands (; es, Islas Malvinas, link=no ) is an archipelago in the South Atlantic Ocean on the Patagonian Shelf. The principal islands are about east of South America's southern Patagonian coast and about from Cape Dubou ...

Description

The bulk of the formation originates from

silicic Silicic is an adjective to describe magma or igneous rock rich in silica. The amount of silica that constitutes a silicic rock is usually defined as at least 63 percent. Granite and rhyolite are the most common silicic rocks. Silicic is the group ...

pyroclastic material during a period of

bimodal volcanism Bimodal volcanism is the eruption of both mafic and felsic lavas from a single volcanic centre with little or no lavas of intermediate composition. This type of volcanism is normally associated with areas of extensional tectonics, particularly rif ...

in Rocas Verdes Basin, a

rift In geology, a rift is a linear zone where the lithosphere is being pulled apart and is an example of extensional tectonics. Typical rift features are a central linear downfaulted depression, called a graben, or more commonly a half-grabe ...

basin Basin may refer to: Geography and geology * Depression (geology) ** Back-arc basin, a submarine feature associated with island arcs and subduction zones ** Debris basin, designed to prevent damage from debris flow ** Drainage basin (hydrology), ...

.Fildani, Andrea, Romans, B.W., Fosdick, J.C., Crane, W.H., and Hubbard, S.M. (2008)
Orogenesis of the Patagonian Andes as reflected by basin evolution in southernmost South America
in Spencer, J.E., and Titley, S.R., eds., Ores and orogenesis: Circum-Pacific tectonics, geologic evolution, and ore deposits: ''Arizona Geological Society Digest'' 22: 259-268. The Tobífera Formation is grouped together with other formations of similar age in Patagonia in the Chon Aike Province an extraordinarily large province of silicic volcanism. Except for some western and southern exposures most of the formation is buried and known only from

borehole A borehole is a narrow shaft bored in the ground, either vertically or horizontally. A borehole may be constructed for many different purposes, including the extraction of water ( drilled water well and tube well), other liquids (such as petro ...

s in the

Magallanes Magallanes may refer to: * Ferdinand Magellan (1480–1521), Portuguese explorer who led part of the first expedition around the world * Strait of Magellan, the strait between the Pacific and Atlantic Oceans, located in Chile Places * Magallane ...

and

s. The formation is equivalent to El Quemado and Ibañez Formations. Tobífera Formation has an up to thick Basal Clastic Complex, a sub-unit made up of

conglomerate Conglomerate or conglomeration may refer to: * Conglomerate (company) * Conglomerate (geology) * Conglomerate (mathematics) In popular culture: * The Conglomerate (American group), a production crew and musical group founded by Busta Rhymes ** C ...

and

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 ...

. Tobífera Formation

unconformably 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 o ...

overlies

metamorphic 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, cau ...

and

igneous Igneous rock (derived from the Latin word ''ignis'' meaning fire), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rock is formed through the cooling and solidification of magma o ...

basement A basement or cellar is one or more Storey, floors of a building that are completely or partly below the storey, ground floor. It generally is used as a utility space for a building, where such items as the Furnace (house heating), furnace, ...

complexes of Cambrian age.

Deformation and metamorphism

Much of the formation is folded and faulted as consequence of the

Andean orogeny The Andean orogeny ( es, Orogenia andina) is an ongoing process of orogeny that began in the Early Jurassic and is responsible for the rise of the Andes mountains. The orogeny is driven by a reactivation of a long-lived subduction system along ...

. At

Última Esperanza Province Última Esperanza ( es, Provincia de Última Esperanza, meaning "Last Hope Province") is one of four provinces in the southern Chilean region of Magallanes and Antártica Chilena. The capital is Puerto Natales and it is named after Última E ...

the formation

metamorphosed 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, causi ...

first under

greenschist facies Greenschists are metamorphic rocks that formed under the lowest temperatures and pressures usually produced by regional metamorphism, typically and 2–10 kilobars (). Greenschists commonly have an abundance of green minerals such as chlorite, ...

and then under

prehnite-pumpellyite facies The prehnite-pumpellyite facies is a metamorphic facies typical of subseafloor alteration of the oceanic crust around mid-ocean ridge spreading centres. It is a metamorphic grade transitional between zeolite facies and greenschist facies repres ...

conditions. Some

rhyolite Rhyolite ( ) is the most silica-rich of volcanic rocks. It is generally glassy or fine-grained ( aphanitic) in texture, but may be porphyritic, containing larger mineral crystals ( phenocrysts) in an otherwise fine-grained groundmass. The min ...

s of Tobífera Formation were incorporated into

Cordillera Darwin Metamorphic Complex The Cordillera Darwin Metamorphic Complex is a geologic complex composed chiefly of metamorphic rocks located in southern Tierra del Fuego. It has been suggested that the Cordillera Darwin Metamorphic Complex is analogous to the Eastern Andes Meta ...

. The incorporation of part of Tobífera Formation in the metamorphic complex was accompanied by deformation and metamorphism and occurred in the context of the Andean orogeny in the

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 ...

References

{{DEFAULTSORT:Tobifera Formation Geologic formations of Chile Geologic formations of Argentina Jurassic System of South America Jurassic Argentina Jurassic Chile Jurassic volcanism Tuff formations Formations Geology of Magallanes Region Geology of Santa Cruz Province, Argentina Geology of Patagonia Geology of the Atlantic Ocean