Hakatai Shale

Hakatai Shale
Stratigraphic range:
Meso-Proterozoic,
1,200±50 Ma?
Three approximate equal-thickness formations outcropping below Isis Temple-prominence at north perimeter, Granite Gorge
(Unkar Group)–Shinumo Quartzite (vertical cliffs), upon basalt sills, upon orange-red Hakatai Shale, upon Bass Formation.
Dk blackish canyons are the Granite Gorge Vishnu Basement Rocks.
TypeGeological formation
Unit ofUnkar Group
UnderliesShinumo Quartzite
OverliesBass Formation
Thickness300 m (980 ft) approximate maximum
Lithology
Primaryshale
Othersiltstone, sandy siltstone, and sandstone (subarkose, arkose and quartz arenite)
Location
RegionArizona, Grand Canyon
Isis Temple region, southwest Bright Angel Canyon, at north side, Granite Gorge, and along Colorado River, also,
numerous side canyons to Granite Gorge / Colorado River
CountryUnited States
(Southwest United States)
Type section
Named forHakatai Canyon
Named byNoble (1914)[1]
Basalt dike in orange-red Hakatai Shale along Colorado River at Hance Rapid, river mile 76.5, Grand Canyon.
Many layers of rock. Tonto Group and Unkar units. Shows the Vishnu rocks; but also the orange Hakatai Shale, Shinumo Quartzite, some Bass Formation?, etc. The upper massive layers show the white cliffs of Coconino Sandstone over the Supai Group redbeds that sit upon the Redwall Limestone.
Geologic stratigraphic column of strata exposed in and near the Grand Canyon showing stratigraphic units and major unconformities.[2]

The Hakatai Shale is a Mesoproterozoic rock formation with important exposures in the Grand Canyon, Coconino County, Arizona. It consists of colorful strata that exhibit colors varying from purple to red to brilliant orange. These colors are the result of the oxidation of iron-bearing minerals in the Hakatai Shale. It consists of lower and middle members that consist of bright-red, slope-forming, highly fractured, argillaceous mudstones and shale and an upper member composed of purple and red, cliff-forming, medium-grained sandstone. Its thickness, which apparently increases eastwards, varies from 137 to 300 m (449 to 984 ft). In general, the Hakatai Shale and associated strata of the Unkar Group rocks dip northeast (10–30°) toward normal faults that dip 60° or more toward the southwest. This can be seen at the Palisades fault in the eastern part of the main Unkar Group outcrop area (below East Rim). In addition, thick, prominent, and dark-colored basaltic sills and dikes cut across the purple to red to brilliant orange strata of the Hakatai Shale.[3][4][5]

The bright orange-red slopes of the Hakatai Shale contrasts sharply against the grayish outcrops of the Bass Formation. The outcrop of the Hakatai Shale also contrasts greatly with the steep cliffs formed by Shinumo Quartzite as seen at the base of Isis Temple. In the central Grand Canyon north of Grand Canyon Village and viewed from the south at the South Rim, the bright orange-red unit can be seen below the Isis Temple and Cheops Pyramid landforms at the intersection of Bright Angel Canyon and Granite Gorge; the Bright Angel Trail from the South Rim traverses through the geographic region to the north, the North Kaibab Trail in Bright Angel Canyon.[3][5]

The Hakatai Shale is part of a conformable sequence of sedimentary strata that comprise the Unkar Group. The Unkar Group is about 1,600 to 2,200 m (5,200 to 7,200 ft) thick and composed, in ascending order, of the Bass Formation, Hakatai Shale, Shinumo Quartzite, Dox Formation, and Cardenas Basalt. In ascending order, the Unkar Group is overlain by the Nankoweap Formation, about 113 to 150 m (371 to 492 ft) thick; the Chuar Group, about 1,900 m (6,200 ft) thick; and the Sixtymile Formation, about 60 m (200 ft) thick. The Grand Canyon Supergroup, of which the Unkar Group is the lowermost part, overlies deeply eroded granites, gneisses, pegmatites, and schists that comprise Vishnu Basement Rocks.[3][6][7]

  1. ^ Noble, LF (1914) The Shinumo Quadrangle, Grand Canyon District, Arizona. Bulletin. no. 549. US Geological Survey, Reston, Virginia. 100 pp.
  2. ^ Karlstrom, K., Crossey, L., Mathis, A., and Bowman, C., 2021. Telling time at Grand Canyon National Park: 2020 update. Natural Resource Report NPS/GRCA/NRR—2021/2246. National Park Service, Fort Collins, Colorado. 36 pp.
  3. ^ a b c Hendricks, JD, and GM Stevenson (2003) Grand Canyon Supergroup: Unkar Group. In SS Beus and M Morales, eds., pp. 39–52, Grand Canyon Geology, 2nd ed. Oxford University Press, New York.
  4. ^ Billingsley, GH (2000) Geologic Map of the Grand Canyon 30 × 60 Quadrangle, Coconino and Mohave Counties, Northwestern Arizona, Pamphlet to accompany Geologic Investigations Series I–2688 Version 1.0.U.S. Geological Survey, Reston, Virginia. 15 pp.
  5. ^ a b Beus, SS, RR Rawson, RO Dalton, GM Stevenson, VS Reed, and TM Daneker (1974) Preliminary report on the Unkar Group (Precambrian) in Grand Canyon, Arizona. In TNV Karlstrom, GA Swann, and RL Eastwood, ed., pp. 34–53, Geology of northern Arizona, with notes on archaeology and paleoclimate; Part 1, Regional studies. Geological Society of America, Rocky Mountain Section, Boulder, Colorado. 407 pp.
  6. ^ Elton, DP, and EH McKee (1982) Age and correlation of the late Proterozoic Grand Canyon disturbance, northern Arizona. Geological Society of America Bulletin. 93(8): 681–99.
  7. ^ Karlstrom, KE, BR Ilg, Bradley, D Hawkins, ML Williams, G Dumond, KK. Mahan, and SA Bowring, Samuel (2012) Vishnu Basement Rocks of the Upper Granite Gorge: Continent formation 1.84 to 1.66 billion years ago. In JM Timmons and KE Karlstrom, eds., pp. 7–24, Grand Canyon geology: Two billion years of earth's history. Special Paper no 294, Geological Society of America, Boulder, Colorado.