Geology of New Mexico

The geology of New Mexico includes bedrock exposures of four physiographic provinces, with ages ranging from almost 1800 million years (Ma) to nearly the present day.

The geologic history of the state began with its assembly during the Yavapai and Mazatzal orogenies 1750 to 1650 million years ago (Mya).

Over a thousand million years of tectonic quiescence followed, ending with the rise of the Ancestral Rocky Mountains in Pennsylvanian time, 300 Mya.

The Permian and most of the Mesozoic were another interval of relative tectonic quiescence, where gradual subsidence deposited formations that preserve an impressive stratigraphic record across the state.

This ended with the Laramide orogeny, beginning around 70 Mya, which elevated most of the mountain ranges of modern New Mexico and was accompanied by violent volcanic activity.

Most of New Mexico has a semiarid to arid climate, and ground water in aquifers is an important geologic resource for farmers and municipal areas.

[5][6] Rocks exposed in the southern Rocky Mountains are as old as nearly 1800 million years (Ma),[7] while some volcanic flows in the state are geologically very young.

This extends from central Colorado to northern Chihuahua, Mexico, passing from north to south through the center of the state, cutting across the southern Rocky Mountains and the Basin and Range provinces, and roughly coinciding with the valley of the Rio Grande River.

[14] The island arcs were carried into a subduction zone along the margin of Laurentia, the ancient core of North America, around 1700 million years ago, an event called the Yavapai orogeny.

The rocks now exposed at the surface were uplifted during the Paleozoic, the early Cenozoic Laramide orogeny as well as block faulting and tilting in the more recent geologic past.

Metavolcanic rocks in the Tusas Mountains may be among the oldest, which are intruded by 1.65 billion year old trondhjemite, but display more than one metamorphic fabric.

Precambrian rocks formed volcanogenic polymettalic sulfides, rich in gold, silver and tungsten, kyanite, copper veins and pegmatite with beryllium, lithium, niobium, tantalum and mica.

[19] The region was tectonically quiescent until around 1400 Mya, when the poorly understood Picuris orogeny deformed and metamorphosed much of the crust of New Mexico.

[26] By the late Paleozoic, in the Pennsylvanian and Permian, the rise of the Ancestral Rocky Mountains broke the ancient peneplain into basins separated by uplifts.

[35] This pattern continued into the late Triassic, when the climate become somewhat cooler and wetter, and a substantial river system developed through New Mexico that deposited the Chinle Group.

[36][37] The Rock Point Formation of the Chinle Group preserved large numbers of fossils of Coelophysis, one of the earliest known genera of dinosaurs.

[40] This was followed by flooding of northern New Mexico by an arm of the Sundance Sea, leading to deposition of the limestone and gypsum beds of the Todilto Formation.

[43][44] Towards the end of the Cretaceous, shallow subduction of the Farallon plate drove the Laramide orogeny, which uplifted the Rocky Mountains and lasted into the Cenozoic.

The vast Mogollon-Datil volcanic field was active during this time, as were the smaller Latir volcanic field and the Ortiz porphyry belt[50][45] The rise of hot asthenosphere below New Mexico reversed the compression of the crust and put it into tension, resulting in the opening of the Rio Grande rift,[51][52] beginning about 30 Mya,[53] and the development of Basin and Range geology across the southern part of the state.

Rising costs and depleted ore bodies have led to widespread abandonment and ghost towns throughout the state, which remain comparatively well-preserved in the dry climate.

[59] Because of New Mexico's typically semiarid climate, ground water in aquifers is an important geologic resource for farmers[63] and municipal areas.

[64] The groundwater potential of the Santa Fe Group was recognized by Kirk Bryan in 1938,[65] and the Alamosa subbasin of the San Luis Valley, the central part of the Albuquerque Basin, and the southern Mesilla basin from Las Cruces to El Paso are now among the most productive groundwater reservoirs in the western United States.