The Mazatzal Group is a

group A group is a number of persons or things that are located, gathered, or classed together. Groups of people * Cultural group, a group whose members share the same cultural identity * Ethnic group, a group whose members share the same ethnic iden ...

geologic formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exp ...

s that crops out in portions of central

Arizona Arizona ( ; nv, Hoozdo Hahoodzo ; ood, Alĭ ṣonak ) is a state in the Southwestern United States. It is the 6th largest and the 14th most populous of the 50 states. Its capital and largest city is Phoenix. Arizona is part of the Fou ...

, US.

Detrital zircon geochronology Detrital zircon geochronology is the science of analyzing the age of zircons deposited within a specific sedimentary unit by examining their inherent radioisotopes, most commonly the uranium–lead ratio. Zircon is a common accessory or trace ...

establishes a maximum age for the formation of 1660 to 1630 million years ( Mya), in the

Statherian The Statherian Period (; grc, σταθερός, statherós, meaning "stable, firm") is the final geologic period in the Paleoproterozoic Era and lasted from Mya to Mya (million years ago). Instead of being based on stratigraphy, these dates ar ...

period Period may refer to: Common uses * Era, a length or span of time * Full stop (or period), a punctuation mark Arts, entertainment, and media * Period (music), a concept in musical composition * Periodic sentence (or rhetorical period), a concept ...

of the

Precambrian The Precambrian (or Pre-Cambrian, sometimes abbreviated pꞒ, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of the ...

. The group gives its name to the

Mazatzal orogeny The Mazatzal orogeny was an orogenic event in what is now the Southwestern United States from 1650 to 1600 Mya in the Statherian Period of the Paleoproterozoic. Preserved in the rocks of New Mexico and Arizona, it is interpreted as the collisi ...

, a mountain-building event that took place between 1695 and 1630 Mya.

Description

The Mazatzal Group consists mostly of fine-grained light-brown to gray

quartzite Quartzite is a hard, non- foliated metamorphic rock which was originally pure quartz sandstone.Essentials of Geology, 3rd Edition, Stephen Marshak, p 182 Sandstone is converted into quartzite through heating and pressure usually related to tect ...

which often shows

cross-bedding In geology, cross-bedding, also known as cross-stratification, is layering within a stratum and at an angle to the main bedding plane. The sedimentary structures which result are roughly horizontal units composed of inclined layers. The origina ...

;

metaconglomerate Metaconglomerate is a rock type which originated from conglomerate after undergoing metamorphism. Conglomerate is easily identifiable by the pebbles or larger clasts in a matrix of sand, silt, or clay. Metaconglomerate looks similar to conglome ...

containing

clasts Clastic rocks are composed of fragments, or clasts, of pre-existing minerals and rock. A clast is a fragment of geological detritus,Essentials of Geology, 3rd Ed, Stephen Marshak, p. G-3 chunks, and smaller grains of rock broken off other rocks ...

up to or more in size; and occasional lenses, up to in thickness, of maroon to gray

argillite :''"Argillite" may also refer to Argillite, Kentucky.'' Argillite () is a fine-grained sedimentary rock composed predominantly of indurated clay particles. Argillaceous rocks are basically lithified muds and oozes. They contain variable amounts ...

showing

ripple mark In geology, ripple marks are sedimentary structures (i.e., bedforms of the lower flow regime) and indicate agitation by water (current or waves) or wind. Defining ripple cross-laminae and asymmetric ripples * ''Current ripple marks'', ''unidi ...

s and

mudcracks Mudcracks (also known as mud cracks, desiccation cracks or cracked mud) are sedimentary structures formed as muddy sediment dries and contracts.Jackson, J.A., 1997, ''Glossary of Geology'' (4th ed.), American Geological Institute, Alexandria, VA, ...

. The lower beds of the group are intruded by

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 mineral ...

domes A dome () is an architectural element similar to the hollow upper half of a sphere. There is significant overlap with the term cupola, which may also refer to a dome or a structure on top of a dome. The precise definition of a dome has been a m ...

and sills. The total thickness of the group is up to . The group lies disconformably on top of the Red Rock Rhyolite and is in turn overlain by the Hopi Springs Shale. The group crops out in the Mazatzal Mountains, where it has been strongly deformed (with up to 50% shortening to the northwest) and in the Prescott area, where it has been only mildly

metamorphosed Metamorphic rocks arise from the transformation of existing rock to new types of rock in a process called metamorphism. The original rock (protolith) is subjected to temperatures greater than and, often, elevated pressure of or more, causin ...

. It is also present in the upper Salt River canyon. The group gives its name to the

, a mountain-building event that took place between 1695 and 1630 Mya.

Members

In the northern Mazatzal Mountains, the Mazatzal Group is divided (in ascending stratigraphic order) into the

Deadman Quartzite Deadman or Deadman's may refer to: * "Deadman" or "dead man", are alternative terms for a dead man's switch * "Deadman's foot" is another name for a Salamander in metallurgy * "Deadman anchor" is a buried object (log, concrete, block, etc.) used ...

, the

Maverick Shale Maverick, Maveric or Maverik may refer to: History * Maverick (animal), an unbranded range animal, derived from U.S. cattleman Samuel Maverick Aviation * AEA Maverick, an Australian single-seat sportsplane design * General Aviation Design Bure ...

, and the Mazatzal Peak Quartzite. In the upper Salt River Canyon, the Mazatzal Group is represented by the

White Ledges Formation The White Ledges Formation is a geologic formation that crops out in central Arizona, US. Detrital zircon geochronology establishes a maximum age for the formation of 1726 million years ( Mya), in the Statherian period of the Precambrian. The f ...

. In the Four Peaks area, the Mazatzal Group is divided (in ascending stratigraphic order) into an informal lower quartzite, an informal lower pelite, and the

Four Peaks Quartzite 4 (four) is a number, numeral and digit. It is the natural number following 3 and preceding 5. It is the smallest semiprime and composite number, and is considered unlucky in many East Asian cultures. In mathematics Four is the smallest c ...

. These are interpreted as a single sequence of sediment deposition. The lower quartzite is an extremely pure quartzite up to thick. The lower pelite is about thick and consists of

pelite A pelite (Greek: ''pelos'', "clay") or metapelite is a metamorphosed fine-grained sedimentary rock, i.e. mudstone or siltstone. The term was earlier used by geologists to describe a clay-rich, fine-grained clastic sediment or sedimentary rock, ...

and

psammite Psammite (Greek: ''psammitēs'' "(made) from sand", from ''psammos'' "sand") is a general term for sandstone. It is equivalent to the Latin-derived term areniteU.S. Bureau of Mines Staff (1996) ''Dictionary of Mining, Mineral, & Related Terms.'' R ...

beds. The Four Peaks Quartzite is up to thick and is mostly extremely pure quartzite with a few

layers.

History of investigation

The unit was first described by E.D. Wilson in 1922 as the Mazatzal Quartzite. It was raised to group rank in 1981 by P. Anderson and W.R. Wirth. The group was assigned to the Tonto Basin Supergroup in 1988 by Karl Karlstrom and Samuel Bowring.

References

{{Reflist Precambrian Arizona Geologic groups of Arizona Quartzite formations