The Ayacara Formation is a sedimentary formation made up of

interbedded In geology, interbedding occurs when beds (layers of rock) of a particular lithology lie between or alternate with beds of a different lithology. For example, sedimentary rocks may be interbedded if there were sea level variations in their sedimen ...

sand Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a soil texture, textur ...

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, ...

cropping out around Hornopirén and

Ayacara Peninsula Ayacara Peninsula is a peninsula in northwestern Patagonia in Chile that protrudes to the northwest. The peninsula bounds to the southwest with Reñihué Fjord and to the northeast with Comau Fjord. The volcano Huequi lies in the central parts of ...

in western

Los Lagos Region Los Lagos Region ( es, Región de Los Lagos , ''Region of the Lakes'') is one of Chile's 16 regions, which are first order administrative divisions, and comprises four provinces: Chiloé, Llanquihue, Osorno and Palena. The region contains ...

, Chile. Less common rocks are

tuff Tuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is lithified into a solid rock. Rock that contains greater than 75% ash is considered tuff, while rock ...

and

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 ...

. The formation dates to the Early and Middle Miocene (no earlier than 21.8–17.6

million years ago The abbreviation Myr, "million years", is a unit of a quantity of (i.e. ) years, or 31.556926 teraseconds. Usage Myr (million years) is in common use in fields such as Earth science and cosmology. Myr is also used with Mya (million years ago). ...

) when it deposited during a

marine transgression A marine transgression is a geologic event during which sea level rises relative to the land and the shoreline moves toward higher ground, which results in flooding. Transgressions can be caused by the land sinking or by the ocean basins filling ...

References

{{Geology of Chile Geologic formations of Chile Miocene Series of South America Aquitanian (stage) Burdigalian Langhian Serravallian Neogene Chile Sandstone formations Siltstone formations Conglomerate formations Tuff formations Geology of Los Lagos Region

See also

References