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Watahomigi Formation

Usage of Geologic Unit Name:
Watahomigi Formation* of Supai Group
Mississippian, Late* (local)
Chesterian, late* (local)
Pennsylvanian, Early*
Morrowan, middle*
Pennsylvanian, Middle*
Atokan, early*
Geologic Province:
Plateau sedimentary province*
Areal Extent:
Type Locality:
Type section: Watahomigi Point, west side of Havasu Canyon about 1 1/2 mi northwest of Supai village, Coconino Co, AZ (McKee, 1975).

Unit Name History:
Named as lowest formation of Supai Group (McKee, 1975). Revised (McKee, 1982). Revised in that rocks previously assigned to the lower part of the Watahomigi Formation are included in the newly named Surprise Canyon Formation (Billingsley, Beus, 1985). Age modified locally (where Surprise Canyon Formation underlies the Watahomigi Formation of the Supai) on basis of conodont biostratigraphy (Martin and Barrick, 1999).

Description from Grand Canyon Area (from Billingsley, George H., 2000)

Watahomigi Formation—Gray and purplish-red, slope-forming limestone, siltstone, mudstone, and conglomerate. Forms an upper ledge/slope unit and a 7 lower slope unit. Upper ledge/slope unit consists of alternating gray, thin-bedded cherty limestone ledges interbedded with purplish-gray siltstone and mudstone; limestone beds contain Lower Pennsylvanian conodont fossils (Martin and Barrick, 1999); red chert lenses and nodules common. Includes limestone chertpebble conglomerate at base, locally containing Lower Pennsylvanian fossils. Upper ledge/slope unit averages about 70 ft (21 m) thick throughout map area. Lower slope unit consists mainly of purplish-red mudstone and siltstone, interbedded with thin-bedded, aphanitic to granular limestone in upper part with red chert veins and nodules. Conodonts in lower thin limestone beds are Upper Mississippian (Martin and Barrick, 1999). Unit includes purple siltstone and gray limestone interbedded with conglomerate that fill small erosion channels cut into either Surprise Canyon Formation or Redwall Limestone. Purple shale and mudstone of lower slope unit unconformably overlies the gray Redwall in majority of map area. Contact with the Surprise Canyon is often based on color change from purple mudstone of the Watahomigi to dark-red mudstone of the Surprise Canyon. Unit averages about 100 ft (30 m) thick along eastern edge of map area, thickening to about 200 ft (60 m) along western edge.


McKee, E.H., 1975, The Supai Group; subdivision and nomenclature, IN Contributions to stratigraphy: U.S. Geological Survey Bulletin, 1395-J, p. J1-J7.

McKee, E.D. (editor), 1982, The Supai Group of Grand Canyon: U.S. Geological Survey Professional Paper, 1173, 504 p.

Billingsley, G.H. and Beus, S.S., 1985, The Surprise Canyon Formation; an Upper Mississippian and Lower Pennsylvanian(?) rock unit in the Grand Canyon, Arizona, IN Stratigraphic notes, 1984: U.S. Geological Survey Bulletin, 1605-A, p. A27-A33.

Martin, Harriet, and Barrick, J.E., 1999, Conodont biostratigraphy, chapter F, in Billingsley, G.H., and Beus, S.S., editors, Geology of the Surprise Canyon Formation of the Grand Canyon, Arizona: Museum of Northern Arizona Bulletin 61, p. 97-116.

Billingsley, George H., 2000, Geologic Map of the Grand Canyon 30' by 60' Quadrangle, Coconino and Mohave Counties, Northwestern Arizona: U.S. Geological Survey Geologic Investigation Series I-2688, available on-line at:

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* show accepted USGS usage. Note that data on this page is modified from information available via the National Geologic Map Database GEOLEX:

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