Sierra Baguales or Sierra de los Baguales is a mountain range in the southernmost Andes. Sierra Baguales is a long east–west chain, secondary to the main chain of the Andes that lie further west. It lies along the border between Chile and Argentina near the localities of

Puerto Natales Puerto Natales is a city in Chilean Patagonia. It is the capital of both the commune of Natales and the province of Última Esperanza, one of the four provinces that make up the Magallanes and Antartica Chilena Region in the southernmost part of ...

and Río Turbio.

Geology

The mountain range contains a series of

cirque A (; from the Latin word ) is an amphitheatre-like valley formed by Glacier#Erosion, glacial erosion. Alternative names for this landform are corrie (from , meaning a pot or cauldron) and ; ). A cirque may also be a similarly shaped landform a ...

s formed by

glaciers 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 ...

. Many cirques developed in the

Pleistocene Epoch The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...

from isolated glaciers that existed separedly from

ice sheet In glaciology, an ice sheet, also known as a continental glacier, is a mass of glacier, glacial ice that covers surrounding terrain and is greater than . The only current ice sheets are the Antarctic ice sheet and the Greenland ice sheet. Ice s ...

s further west. The rocks of Sierra Baguales belong to various formations of

Magallanes Basin The Magallanes Basin or Austral Basin is a major sedimentary basin in southern Patagonia. The basin covers a surface of about and has a NNW-SSE oriented shape. The basin is bounded to the west by the Andes mountains and is separated from the Mal ...

. These rocks contain fossils of plants, mammals and marine invertebrates.

Stratigraphy

From top to bottom the following formations make up Sierra Baguales: *

Santa Cruz Formation The Santa Cruz Formation is a geological formation in the Magallanes Basin, Magallanes/Austral Basin in southern Patagonia in Argentina and adjacent areas of Chile. It dates to the late Early Miocene epoch, and is contemporaneous with the eponym ...

, sedimentary rocks belonging to a non-marine succession and hosting many vertebrate fossilsBostelmann et al., 2013 * Estancia 25 de Mayo Formation, a succession of fossil-bearing sedimentary rocks that date to the

Early Miocene The Early Miocene (also known as Lower Miocene) is a sub-epoch of the Miocene epoch (geology), Epoch made up of two faunal stage, stages: the Aquitanian age, Aquitanian and Burdigalian stages. The sub-epoch lasted from 23.03 ± 0.05 annum, Ma to ...

. Sediments were deposited in a marine environment. * La Cumbre Formation, an

olivine The mineral olivine () is a magnesium iron Silicate minerals, silicate with the chemical formula . It is a type of Nesosilicates, nesosilicate or orthosilicate. The primary component of the Earth's upper mantle (Earth), upper mantle, it is a com ...

-bearing

gabbro Gabbro ( ) is a phaneritic (coarse-grained and magnesium- and iron-rich), mafic intrusive igneous rock formed from the slow cooling magma into a holocrystalline mass deep beneath the Earth's surface. Slow-cooling, coarse-grained gabbro is ch ...

sill * Río Leona Formation, a succession of non-marine fossils, some of which contain ''

Nothofagus ''Nothofagus'', also known as the southern beeches, is a genus of 43 species of trees and shrubs native to the Southern Hemisphere, found across southern South America (Chile, Argentina) and east and southeast Australia, New Zealand, New Guin ...

'' fossils * Bandurrías Formation, an olivine-bearing gabbro sill *

Loreto Formation Loreto Formation () is a sedimentary formation of Late Eocene age in the southernmost Magallanes Basin. It overlies the Leña Dura Formation and the contact with an overlying formation is not observed.Torres et al., 2009, p.2 From 2013 to 2020 it ...

, sedimentary rocks variously assigned a Late Eocene to Early Miocene age. Contains fossil

shark teeth Sharks continually shed their teeth; some Carcharhiniformes shed approximately 35,000 teeth in a lifetime, replacing those that fall out. There are four basic types of shark teeth: dense flattened, needle-like, pointed lower with triangular up ...

. On the eastern slopes of Sierra Baguales various lithic artifacts have been found. Human occupation of eastern foothills begun no later than 4,500 years before present.

References

Bibliography

* {{Geology of Chile Mountain ranges of Argentina Mountain ranges of Chile Mountains of Magallanes Region Landforms of Santa Cruz Province, Argentina Última Esperanza Province Argentina–Chile border Two-thousanders of the Andes