Muav Limestone

Muav Limestone
Stratigraphic range: Middle Cambrian
502–499 Ma
[1]
representative sequence of Redwall Limestone, Temple Butte Formation, and Muav Limestone, in Grand Canyon
TypeGeological formation
Unit ofTonto Group[2]
Underlieseither the Frenchman Mountain Dolostone (Cambrian) or Redwall Limestone (Mississippian). Locally underlies Temple Butte Formation (Devonian) that fills narrow paleovalleys cut into the Muav Limestone.
OverliesBright Angel Shale
Thickness250 m (820 ft), at maximum
Lithology
Primarylimestone and dolomite
Othershale and intraformational conglomerate.
Location
RegionNorthern Arizona (Grand Canyon), central Arizona, southeast California, southern Nevada, and southeast Utah
CountryUnited States of America
Type section
Named forMuav Canyon, north side of Colorado River[3]
Named byNoble (1914)[3]

The Muav Limestone is a Cambrian geologic formation within the 5-member Tonto Group. It is a thin-bedded, gray, medium to fine-grained, mottled dolomite; coarse- to medium-grained, grayish-white, sandy dolomite and grayish-white, mottled, fine-grained limestone. It also contains beds of shale and intraformational conglomerate. The beds of the Muav Limestone are either structureless or exhibit horizontally laminations and cross-stratification. The Muav Limestone forms cliffs or small ledges that weather a dark gray or rusty-orange color. These cliffs or small ledges directly overlie the sloping surfaces of the Bright Angel Shale. The thickness of this formation decreases eastward from 76 m (249 ft) in the western Grand Canyon to 14 m (46 ft) in the eastern Grand Canyon. To the west in southern Nevada, its thickness increases to 250 m (820 ft) in the Frenchman Mountain region.[2][4]

Beyond the Grand Canyon area, the Muav Limestone is recognized in southern Utah, southern Nevada and southern California.[5] In parts of California, it is known and mapped as the Muav Marble.[6]

  1. ^ 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.
  2. ^ a b 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.
  3. ^ a b Noble, L.F., 1914. The Shinumo quadrangle, Grand Canyon district, Arizona. U.S. Geological Survey Bulletin. 549. doi:10.3133/B549. ISSN 0083-1093.
  4. ^ Middleton, L.T. and Elliott, D.K., 2003. Tonto Group, in Beus, S. S., and Morales, M., eds. Grand Canyon geology Museum of Northern Arizona Press, Flagstaff, Arizona. pp. 90–106.
  5. ^ Wood, W., 1966. Facies Changes in the Cambrian Muav Limestone, Arizona. Geological Society of America Bulletin, 77(11), pp.1235-1246.
  6. ^ Hamilton, W.B., 1987. Mesozoic geology and tectonics of the Big Maria Mountains region, southeastern California. Arizona Geological Society Digest, v. 18, pp. 33-45.