The

Cambrian The Cambrian Period ( ; sometimes symbolized C with bar, Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million ...

Muav Limestone is a

geologic unit A stratigraphic unit is a volume of rock of identifiable origin and relative age range that is defined by the distinctive and dominant, easily mapped and recognizable petrographic, lithologic or paleontologic features (facies) that characterize it ...

within the 5-member

Tonto Group The Tonto Group is a name for an assemblage of related sedimentary strata, collectively known by geologists as a ''Group'', that comprises the basal sequence Paleozoic strata exposed in the sides of the Grand Canyon. As currently defined, the T ...

. It is about thick at its maximum. It is a resistant cliff-forming unit. The Muav consists of dark to light-gray, brown, and orange red

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...

with

dolomite Dolomite may refer to: *Dolomite (mineral), a carbonate mineral *Dolomite (rock), also known as dolostone, a sedimentary carbonate rock *Dolomite, Alabama, United States, an unincorporated community *Dolomite, California, United States, an unincor ...

and calcareous

mudstone Mudstone, a type of mudrock, is a fine-grained sedimentary rock whose original constituents were clays or muds. Mudstone is distinguished from '' shale'' by its lack of fissility (parallel layering).Blatt, H., and R.J. Tracy, 1996, ''Petrology. ...

.Karlstrom, K.E., Mohr, M.T., Schmitz, M.D., Sundberg, F.A., Rowland, S.M., Blakey, R., Foster, J.R., Crossey, L.J., Dehler, C.M. and Hagadorn, J.W., 2020. ''Redefining the Tonto Group of Grand Canyon and recalibrating the Cambrian time scale''. ''Geology'', 48(5), pp. 425–430.Connors, T.B., Tweet, J.S., and Santucci, V.L., 2020. ''Stratigraphy of Grand Canyon National Park''. In: Santucci, V.L., Tweet, J.S., ed., pp. 54–74, ''Grand Canyon National Park: Centennial Paleontological Resource Inventory (Non-sensitive Version) ''. Natural Resource Report NPS/GRCA/NRR—2020/2103. National Park Service, Fort Collins, Colorado, 603 pp. The Muav Limestone is overlain in the western Grand Canyon by the late

Frenchman Mountain Dolostone. Eastward, the Frenchman Mountain Dolostone pinches out and the Mississippian

Redwall Limestone The Redwall Limestone is a resistant cliff-forming unit of Mississippian age that forms prominent, red-stained cliffs in the Grand Canyon, ranging in height from to . Lithology Redwall Limestone consists predominantly of light-olive-gray to ...

, which forms prominent vertical cliffs, directly lies upon the Muav Limestone. The

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 ...

Temple Butte Formation fill deep paleovalleys that have been cut through the Frenchman Mountain Dolostone and into the Muav Limestone. The Muav is in part younger than, and in-part grades into, the

Bright Angel Shale The Cambrian Bright Angel Shale is the middle layer of the three member Tonto Group geologic feature. The 3-rock Tonto section famously sits upon the Great Unconformity because of the highly resistant cliffs of the base layer, vertical Tapeats S ...

, which is less erosion resistant and is categorized as a slope-forming unit. The Muav is about 350 feet thick in the east and reaches about 600 feet thick in the western part of its exposure area in the Grand Canyon.Anonymous (2006d
''Muav Limestone''

. U.S. Geological Survey, Reston, Virginia. The two units lie above the erosion-resistant cliff-forming

Tapeats Sandstone Except where underlain by the Sixtymile Formation, Cambrian Tapeats Sandstone is typically the lowest geologic unit, about thick, at its maximum, of the 5-member Tonto Group. It is famous for being the highly-resistant mostly-horizontal unit abo ...

. In the eastern canyon, the Tapeats Sandstone creates the extremely horizontal Tonto Platform. In west Grand Canyon, the north-south

Toroweap Fault The Toroweap Fault of northwest Arizona and southwest Utah is part of a fault system of the west Grand Canyon region, Arizona, US; also the west perimeter regions of the Coconino and Colorado Plateaus. The Hurricane Fault originates at the T ...

is the west perimeter of the Tonto Platform, and west Grand Canyon is dominated by the erosion resistant unit of the

Esplanade Sandstone The Lower Permian Esplanade Sandstone is a cliff-forming, resistant sandstone, dark red, geologic unit found in the Grand Canyon. The rock unit forms a resistant shelf in the west Grand Canyon, south side of the Colorado River, at the east of t ...

. The

Tonto Trail The Tonto Trail is a hiking trail on the South Rim of the Grand Canyon in Grand Canyon National Park, located in the U.S. state of Arizona. Access The Tonto Trail does not terminate at either rim of the Grand Canyon, but begins along the south ...

is a mostly horizontal trail on the south side of Granite Gorge, on the Tonto Platform. The Tonto Group units were deposited on an ancient

erosion surface In geology and geomorphology, an erosion surface is a surface of rock or regolith that was formed by erosion and not by construction (e.g. lava flows, sediment deposition) nor fault displacement. Erosional surfaces within the stratigraphic reco ...

(

angular unconformity An unconformity is a buried erosion surface, erosional or non-depositional surface separating two Rock (geology), rock masses or Stratum, strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer ...

) on the Vishnu Basement Rocks. The Vishnu sequence has a dip of about 45 degrees. As this long-timeframe unconformity represents about 1,000 million years (1.0 billion years) of non–deposition, tectonic activity and erosion, on the

Vishnu Basement Rocks The Vishnu Basement Rocks is the name recommended for all Early Proterozoic crystalline rocks (metamorphic and igneous) exposed in the Grand Canyon region. They form the crystalline basement rocks that underlie the Bass Limestone of the Unkar G ...

, is called the

Great Unconformity Of the many unconformities (gaps) observed in geological strata, the term Great Unconformity is frequently applied to either the unconformity observed by James Hutton in 1787 at Siccar Point in Scotland,Rance, H (1999''Historical Geology: The Pre ...

. Beyond the Grand Canyon area the Muav occurs in southern

Utah Utah ( , ) is a state in the Mountain West subregion of the Western United States. Utah is a landlocked U.S. state bordered to its east by Colorado, to its northeast by Wyoming, to its north by Idaho, to its south by Arizona, and to it ...

, southern

Nevada Nevada ( ; ) is a U.S. state, state in the Western United States, Western region of the United States. It is bordered by Oregon to the northwest, Idaho to the northeast, California to the west, Arizona to the southeast, and Utah to the east. N ...

and southern

California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...

. In the California occurrence it is known as the Muav Marble.

Geologic sequence

The units of the Tonto Group: * 5 – Frenchman Mountain Dolostone * 4 – Muav Limestone * 3 – Bright Angel Shale * 2 – Tapeats Sandstone (start of transgression series) * 1 – Sixtymile Formation

Gallery – Muav Limestone

File:Grand Canyon National Park, North Kaibab Trail in Redwall 0990 - Flickr - Grand Canyon NPS.jpg, upright=1.2, Muav Limestone cliff example, below

cliff, on the

North Kaibab Trail The North Kaibab Trail is a hiking trail in the North Rim side of the Grand Canyon, in Grand Canyon National Park, located in the U.S. state of Arizona. Access Access to this part of the park by car is seasonal, open from mid-May to mid-Octobe ...

(closeup photos, often show purple erosion debris)(expandable photo) File:Grand Canyon01.jpg, (view due-north, northeast, from

Bright Angel Trail The Bright Angel Trail is a hiking trail located in Grand Canyon National Park in the U.S. state of Arizona. Description The trail originates at Grand Canyon Village on the south rim of the Grand Canyon, descending 4380 feet to the Colorado ...

, (''South Rim section'') – View of south-draining Bright Angel Canyon, containing in its lowest section with the Tapeats Sandstone, upon the Granite Gorge, the ''cliffs of gray-brown'' Muav Limestone (25% at base of

), laid upon the ''slope-forming & greenish'' Bright Angel Shale. (The trail also descends/ascends through units on the South Rim, at near photo view.) File:Grand Canyon-Mather point.jpg, View to Sumner Butte, Redwall Limestone peak & vertical cliff, sitting on Muav Limestone

References

External links

{{commons category, Muav Limestone * Abbot, W, (2001
''Revisiting the Grand Canyon – Through the Eyes of Seismic Sequence Stratigraphy.''Search and Discovery Article # 40018
America Association of Petroleum Geologists, Tulsa, Oklahoma. * Anonymous (2006a

U.S. Geological Survey, Reston, Virginia. * Anonymous (2006b

U.S. Geological Survey, Reston, Virginia. * Anonymous (2006c

U.S. Geological Survey, Reston, Virginia. * Anonymous (2006d

U.S. Geological Survey, Reston, Virginia. * Hartman, J. H. (2001
''Muav Limestone, Grand Canyon National Park, Coconino County, Arizona.''GeoDIL, A Geoscience Digital Image Library
University of North Dakota, Grand Forks, North Dakota. * Mathis, A., and C. Bowman (2007
''The Grand Age of Rocks: The Numeric Ages for Rocks Exposed within Grand Canyon''Grand Canyon National Park, Arizona
National Park Service, Grand Canyon National Park, Arizona. * Noble, L. F. (1923a
Unconformity between Temple Butte limestone and Muav limestone, Coconino County, Arizona, Plate 22-A.
Reston, Virginia. * Noble, L. F. (1923b
Unconformity between Temple Butte limestone and Muav limestone, Coconino County, Arizona, Plate 22-B.
Reston, Virginia. * Noble, L. F. (1923c
Unconformity between Temple Butte limestone and Muav limestone, Coconino County, Arizona, Plate 23-A.
Reston, Virginia. * Rowland, S. (nda
Department of Geoscience
University of Nevada, Las Vegas, Nevada. * Rowland, S. (ndb
Department of Geoscience
University of Nevada, Las Vegas, Nevada. * Stamm, N. (2013
National Geologic Database
U.S. Geological Survey, Reston, Virginia. * Timmons, S. S. (2003

National Park Service, Grand Canyon National Park, Arizona. Limestone formations of the United States Natural history of the Grand Canyon Geologic formations of Arizona Geologic formations of Nevada Cambrian Arizona Cambrian Nevada Cambrian System of North America

Geologic sequence

Gallery – Muav Limestone

See also

References

Further reading

External links