Dox Formation

Dox Formation
Stratigraphic range: Mesoproterozoic,
1,140–1,104 Ma
Dox Formation at Tanner Graben-(photo left, on river) and upstream on Colorado River (from Comanche Point, East Rim)
TypeGeological formation
Unit ofUnkar Group
Sub-unitsEscalante Creek Member,
Solomon Temple Member,
Comanche Point Member, and
Ochoa Point Member
UnderliesCardenas Basalt
OverliesShinumo Quartzite
Thickness350 to 410 m (1,150 to 1,350 ft)
Lithology
Primarysandstone
Othermudstone, dolomite, shale; interbedded basalt
Location
RegionArizona, Grand Canyon
Isis Temple region, southwest Bright Angel Canyon, at north side, Granite Gorge, and along Colorado River
CountryUnited States of America
Type section
Named forDox Castle, north side of Colorado River, Shinumo quadrangle, Coconino County, Arizona.
Named byNoble (1914)[1]

The Dox Formation, also known as the Dox Sandstone, is a Mesoproterozoic rock formation that outcrops in the eastern Grand Canyon, Coconino County, Arizona. The Dox Formation comprises the bulk of the Unkar Group, the older subdivision of the Grand Canyon Supergroup. The Unkar Group is about 1,600 to 2,200 m (5,200 to 7,200 ft) thick and composed of, in ascending order, the Bass Formation, Hakatai Shale, Shinumo Quartzite, Dox Formation, and Cardenas Basalt. The Unkar Group is overlain in ascending order 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 entire Grand Canyon Supergroup overlies deeply eroded granites, gneisses, pegmatites, and schists that comprise Vishnu Basement Rocks.[2][3][4]

Purple colored, layered Dox Formation, below black Cardenas Basalt.
(shows the ~15 degree dip)

The Dox Formation contains thick basaltic sills and a number of small, dark dikes. In the area of Desert View and west of Palisades of the Desert, the basaltic sills form very prominent, dark gray cliffs.[2][5]

The Dox Formation takes its name from frontier educator Virginia Dox, the first white woman to explore the Grand Canyon, for whom the Dox Castle butte was named.[6]

  1. ^ Noble, LF (1914) The Shinumo Quadrangle, Grand Canyon District, Arizona. Bulletin. no. 549. US Geological Survey, Reston, Virginia. 100 pp.
  2. ^ a b Cite error: The named reference HendricksOthers2003a was invoked but never defined (see the help page).
  3. ^ 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):681–699.
  4. ^ 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.
  5. ^ Elston, DP (1989) Middle and late Proterozoic Grand Canyon Supergroup, Arizona. In DP Elston, GH Billingsley, and RA Young, RA., eds., pp. 94–105, Geology of the Grand Canyon, Northern Arizona (with Colorado River Guides). American Geophysical Union Fieldtrip Guidebook T115/315 for International Geologic Congress, 28th. American Geophysical Union, Washington DC. 239 pp.
  6. ^ Wright, Lauren A.; Troxel, Bennie W. (2002). Levi Noble, Geologist. United States Geological Survey. p. 7.