The Doña Ana Mountains are a

mountain range A mountain range or hill range is a series of mountains or hills arranged in a line and connected by high ground. A mountain system or mountain belt is a group of mountain ranges with similarity in form, structure, and alignment that have arise ...

in Doña Ana County, New Mexico. The highest elevation in the range is Doña Ana Peak at 5835 feet / 1779 meters, at .

Description

The Doña Ana Mountains are a small, rugged mountain range in the desert a few kilometers north of the city of

Las Cruces, New Mexico Las Cruces (; "the crosses") is the second-largest city in the U.S. state of New Mexico and the seat of Doña Ana County. As of the 2020 census the population was 111,385. Las Cruces is the largest city in both Doña Ana County and southern Ne ...

and just east of the

Rio Grande The Rio Grande ( and ), known in Mexico as the Río Bravo del Norte or simply the Río Bravo, is one of the principal rivers (along with the Colorado River) in the southwestern United States and in northern Mexico. The length of the Rio ...

. The range is bounded by escarpments to the east and south. Doña Ana Peak is located in the southeastern part of the range, where it is prominent viewed from Las Cruces, and Summerford Mountain is prominent in the northeast corner of the range. The range is heavily eroded and largely barren of vegetation, exposing some of bedrock.

Geology

The mountains were formed in the late

Tertiary Tertiary ( ) is a widely used but obsolete term for the geologic period from 66 million to 2.6 million years ago. The period began with the demise of the non- avian dinosaurs in the Cretaceous–Paleogene extinction event, at the start ...

as a fault block, which was uplifted on the east side along the Jornada fault and subsided to the west along the Robledo fault. This tilted the block by about 15 degrees towards the west. The northern part of the mountains is underlain by

Pennsylvanian Pennsylvanian may refer to: * A person or thing from Pennsylvania * Pennsylvanian (geology) The Pennsylvanian ( , also known as Upper Carboniferous or Late Carboniferous) is, in the International Commission on Stratigraphy, ICS geologic timesca ...

and

Permian The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last period of the Pale ...

sedimentary rock Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particle ...

, with a large syenite

sill Sill may refer to: * Sill (dock), a weir at the low water mark retaining water within a dock * Sill (geology), a subhorizontal sheet intrusion of molten or solidified magma * Sill (geostatistics) * Sill (river), a river in Austria * Sill plate, a ...

at Summerford Mountain. The middle section is

Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', " ...

lava flows and volcaniclastics (broken volcanic debris) of the

Palm Park Formation The Palm Park Formation is a geologic formation in southern New Mexico. It preserves fossils dating back to the Eocene epoch. Description The formation consists of reddish clastic sediments, including some beds of boulder conglomerate with ...

, which were erupted about 43 million years ago. The southern part of the range exposes part of the Dona Ana

caldera A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcano eruption. When large volumes of magma are erupted over a short time, structural support for the rock above the magma chamber ...

, which formed during the eruption of the Dona Ana

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 ...

about 36 million years ago. Beds of the Dona Ana Rhyolite ash flow

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 ...

are up to thick. The Summerford Mountain sill was intruded somewhat later, at around 33 million years ago.

Mining

The mountains contain limited volcanic- epithermal vein deposits. These are minerals deposited in fractures by hot groundwater associated with the Dona Ana caldera. Limited mining of these deposits took place during the early 1900s, producing just $5000 in copper, silver, and gold. There is limited potential for lead-zinc, gold skarn, and carbonate-hosted replacement ores at depth below the surface.

Marble Marble is a metamorphic rock composed of recrystallized carbonate minerals, most commonly calcite or dolomite. Marble is typically not foliated (layered), although there are exceptions. In geology, the term ''marble'' refers to metamorpho ...

has been quarried in small amounts for crushed stone from the mountains.

References

{{DEFAULTSORT:Dona Ana Mountains Mountain ranges of New Mexico Mountain ranges of Doña Ana County, New Mexico Organ Mountains–Desert Peaks National Monument