The Sierra del Tontal is a mountain range in the southern part of

San Juan Province, Argentina San Juan Province () is a province of Argentina, located in the western part of the country. Neighbouring provinces are, moving clockwise from the north, La Rioja, San Luis and Mendoza. It borders with Chile to the west. The province has an a ...

. The range is in the

precordillera Precordillera is a Spanish geographical term for hills and mountains lying before a greater range, foothills. The term is derived from ''cordillera'' (mountain range)—literally "pre-mountain range"—and applied usually to the Andes. Some places ...

area of

La Rioja La Rioja () is an autonomous community and province in Spain, in the north of the Iberian Peninsula. Its capital is Logroño. Other cities and towns in the province include Calahorra, Arnedo, Alfaro, Haro, Santo Domingo de la Calzada, and N� ...

, San Juan and Mendoza, in the Cuyo region. It extends south of the

Sierra del Tigre Sierra del Tigre is a mountain range in northeastern Sonora, Mexico at the northern region of the Sierra Madre Occidental. The region contains sky island mountain ranges, called the Madrean Sky Islands, some separated from the Sierra Madre Occid ...

, from which it is separated by the valley of the San Juan River. Its southern foothills are located in

Mendoza Province Mendoza, officially Province of Mendoza, is a province of Argentina, in the western central part of the country in the Cuyo region. It borders San Juan to the north, La Pampa and Neuquén to the south, San Luis to the east, and the republic o ...

. The city of San Juan is located east of the mountains and the Calingasta valley to the west. The range extends for about in a northwest–southeast direction. The highest point is the Ojo de Agua mountain at . Most of the range extends to the south of this peak, and is over in elevation. The rocks include

greywacke Greywacke or graywacke (German ''grauwacke'', signifying a grey, earthy rock) is a variety of sandstone generally characterized by its hardness, dark color, and poorly sorted angular grains of quartz, feldspar, and small rock fragments or lit ...

s and

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especial ...

s. The fossil remains of plants that probably date to the middle or upper

Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, whe ...

period are found in the shales.

References

Citations Sources * Mountain ranges of Argentina Landforms of San Juan Province, Argentina {{SanJuanAR-geo-stub