Surprise Canyon Formation

Usage of Geologic Unit Name:
Surprise Canyon Formation*
Mississippian, Late*
Chesterian, late*

Late Mississippian - 320 million years (age used by National Park Service; Mathis and Bowman, 2005)
Geologic Province:
Plateau sedimentary province*
Areal Extent:
Type Locality:
Type section: Tributary canyon of Colorado River about 3 mi southeast of Bat Tower Overlook (Long 113 deg, 48 min, Lat 36 deg) and 18 km west of Surprise Canyon, for which unit is named, Mohave Co, AZ (Billingsley, Beus, 1985).
Description from Grand Canyon Area (from Billingsley, George H., 2000)

Surprise Canyon Formation (Upper Mississippian)—Dark-reddish-brown siltstone and sandstone, gray limestone and dolomite, and grayish-white chert conglomerate in dark-red or black sandstone matrix. Formation locally absent throughout map area; present only in paleovalleys and karst caves eroded into top half of Redwall Limestone (Mr). Consists of an upper slope unit, a middle cliff unit, and a lower slope unit in western half of map area; forms slope in eastern half of map area. Upper slope unit consists of red-brown, thin-bedded siltstone, calcareous sandstone, and reddish-gray, thin-bedded sandy limestone. Contains numerous ripple marks and marine fossils. Thickness ranges from about 50 to 75 ft (15 to 23 m). Middle cliff unit consists of a reddish-gray, thin-bedded, coarse-grained silty and sandy limestone containing numerous marine fossils. Average thickness about 50 ft (15 m) in western third of map area, thinning and pinching out eastward in eastern two-thirds of map area. Lower slope unit consists of dark-redbrown to black, iron-stained, thin-bedded, coarse- to medium-grained siltstone, sandstone, limestone, and conglomerate. Sandstone and siltstone beds contain numerous plant fossils, bone fossils, mudcracks, and ripplemarks. Sandstone is coarse grained and thin bedded with some low-angle, cross-beditors Conglomerate beds consists of white and gray chert clasts supported in dark-red to black, coarse-grained chert sandstone or gravel matrix, all derived from the Redwall. Thickness of lower unit about 3–60 ft (1–18 m), averaging about 25 ft (8 m). In eastern half of map area, the Surprise Canyon consists mainly of dark-red-brown, slope-forming, massive to thin-bedded, poorly sorted siltstone and sandstone, containing localized plant fossils. The Surprise Canyon is the most fossiliferous rock unit in the Grand Canyon. Overall, thickness averages about 145 ft (45 m) in western half of map area, thinning to less than 50 ft (15 m) in eastern half.
Unit Name History:
Named (Billingsley, Beus, 1985). Age modified on basis of conodont biostratigraphy (Martin, 1992).

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

Beus, S.S., 1990, Redwall Limestone And Surprise Canyon Formation. In: Beus, S.S., Morales, M., editors, Grand Canyon Geology, Oxford University Press, New York, p. 119-145.

Martin, Harriet, 1992, Conodont Biostratigraphy and Paleoenvironment of the Surprise Canyon Formation (Late Mississippian), Grand Canyon, Arizona, 298 p.

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:

Mathis, A. and Bowman, C., 2005, What's in a number? Numeric ages for rocks exposed within the Grand Canyon, Part 2: Nature Notes ( Grand Canyon National Park ), v. 21, no. 2, p. 1-5.

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Note that data on this page contains information that has been partly revised from bibliographic resources available via the National Geologic Map Database GEOLEX:
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Last modified: 1/7/2011