Study Guide: Paleozoic & Mesozoic Geology of Northern NM

Colorado Plateau

A major physiographic province characterized by elevated terrain and dissected plateaus.

Rio Grande Rift

A tectonic feature that represents an area of extension in the Earth's crust, forming a major drainage basin.

Jemez Lineament

A linear volcanic alignment formed during the Late Cenozoic Volcanics (~15 million years ago).

Great Plains

A broad expanse of flat land that stretches across the central United States, characterized by grassland.

Yavapai Orogeny

An orogenic event between 1.75 and 1.68 billion years ago, characterized by the attachment of island arcs to North America.

Mazatzal Orogeny

An orogenic event between 1.65 and 1.60 billion years ago that led to further expansion of the Earth's crust.

Grenville Orogeny

An orogenic event between 1.3 and 1.0 billion years ago, involving the collision of Laurentia with the African and South American cratons.

The Great Unconformity

A significant gap in geologic time marked by older Precambrian rocks covered by much younger Cambrian sandstones.

Vadito Group

Precambrian metavolcanic and metamorphic rocks dating around 1.7-1.72 billion years.

Hondo Group

A formation including quartzite and schists from the Precambrian period.

Marqueñas Formation

A formation with cross-bedded quartzite dated around 1.47 billion years using zircon dating.

Gilman Tunnels

A location containing Precambrian granite that has been metamorphosed into granitic gneiss.

Osha Canyon

A limestone formation overlying Precambrian granite, representing part of a shallow sea environment.

Environmental change in Abo & Yeso sediments

Indicates a transition from a marine environment to a river system, with Abo representing fluvial conditions.

Coelophysis bauri

A dinosaur fossil found in the Chinle Formation.

Limnoscelis

A primitive reptile fossil also found in the Chinle Formation.

Entrada Sandstone

A geological formation characterized by eolian dunes, indicative of ancient wind patterns.

Morrison Formation

A Late Jurassic formation filled with dinosaur fossils indicative of a humid floodplain.

Dakota Sandstone

A formation reflecting marine transgressions and regressions in the Western Interior Seaway.

Uranium Mining start date

Uranium mining in the Grants district began in 1948.

USAEC Role

The U.S. Atomic Energy Commission regulated uranium mining starting in 1947.

Peak uranium production year

The peak uranium production year in the Grants District was 1987.

Reasons for mine closures by 1989

Closures were due to overproduction, the Three Mile Island incident, rising operational costs, and better deposits elsewhere.

Primary uranium-bearing formation

The Morrison Formation, especially its Westwater Canyon Member.

Three uranium deposit types

Primary, redistributed, and remnant deposits characterized by their ore content and structural features.

Jurassic uranium source

Altered volcanic ash and shale from the Jurassic volcanic arcs west of the Morrison Basin.

Triassic formations in Northern New Mexico

Include Moenkopi Formation and Chinle Group.

Jurassic formations in Northern New Mexico

Include Entrada Sandstone, Todilto Formation, and Morrison Formation.

Sonoma Orogeny

An orogenic event around 150 million years ago related to subduction off western North America.

Sevier Orogeny

An orogenic event around 65 million years ago marked by inland subduction shifts.

Transcontinental Arch

A high-elevation landmass that prevented sediment deposition until the Pennsylvanian period.

End-Permian Mass Extinction

A major extinction event (~260-300 million years ago) leading to the loss of approximately 90% of marine species.

Precambrian geology timeframe

Spans from approximately 1.75 billion years ago to 1.35 billion years ago.

Laurentian Shield formation

Resulted from the suturing of continental blocks during Precambrian tectonics.

Coelophysis bauri occurrence

Indicates significant dinosaur findings in the Chinle Formation within the Ghost Ranch area.

Unconformity timeframe

A disconformity of 44 million years exists between the Chinle and Entrada formations.

Gypsum formation process

Formed through the evaporation of saline, oxygen-poor water bodies in Todilto Formation.