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Owl Rock, Kayenta, Navajo Co., Arizona, USAi
Regional Level Types
Owl Rock- not defined -
Navajo Co.County

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Latitude & Longitude (WGS84):
36° 49' 14'' North , 110° 14' 57'' West
Latitude & Longitude (decimal):
Nearest Settlements:
Kayenta5,189 (2011)10.3km
Oljato-Monument Valley154 (2017)19.2km
Oljato-Monument Valley674 (2016)23.3km
Chilchinbito506 (2011)35.8km
Dennehotso746 (2011)35.9km

Located about 7½ miles North of Kayenta. Type locality for the Owl Rock member of the Chinle Formation.


The Owl Rock member of the Chinle formation is made up of cherty limestone and limestone conglomerate beds alternating with claystone, mudstone, and siltstone beds. Wherever this member crops out, the resistant limestone beds form a series of jutting ledges that serve partly to protect the underlying strata. In the Monument Valley area, Arizona, the Owl Rock member is best exposed at its type locality near the base of Owl Rock. Limestone conglomerate beds give way along the strike to massive cherty limestone beds which have subangular to angular nodules of black chert scattered irregularly throughout the beds. A light bluish-gray (5B 7/1) color predominates, although locally greater concentrations of chert tend to darken the limestone beds to gray blue. The ledges formed by these limestone beds normally range from about 2 to 20 feet in thickness and are separated one from another by siltstone and mudstone masses as much as 30 feet thick. The cherty limestone beds weather to form nodular blocky well-jointed ledges. As many as six of these limestone ledges were noted in the Monument Valley area. Of these only five were persistent and could be traced with any degree of confidence.

The Owl Rock member ranges in thickness from about 120 to 166 feet. At Owl Rock the member is 166 feet thick; farther south along Comb Ridge near Chaistla Butte it is about 134 feet thick; to the west along the east flank of Skeleton Mesa it is about 128 feet thick.

A comparable thickness for this unit is reported by Gregory (1917, p. 44-45) who cites a thickness of 152 feet for this member of the Chinle at the mouth of Segihatsosi Canyon near Boot Mesa (pl. 1). The following is presented as the type section of the Owl Rock member of the Chinle formation:

Section of 0wl Rock member of Chinle formation measured at Owl Rock about 7% miles north of Kayenta, Ariz.

Church Rock member of Chinle formation.

Owl Rock member of Chinle formation------------------------ Feet thickness

Limestone, pale-grayish-green, cherty; persistent cliff former; weathers to form blocky masses -------------------------------------- 7
Mudstone, pale-reddish-brown; some intercalated siltstone lenses; forms gentle slopes ----------------------------------------------- 11
Limestone, pale-grayish-green ; includes black angular chert nodules; persistent cliff former ---------------------------------------- 2
Mudstone, pale-reddish-brown; forms gentle slopes -------------------- 2
Limestone, grayish-green; includes black angular chert nodules; cliff former --------------------------------------------------------------- 2
Siltstone, brown, massive, very slightly fissile; locally stands as vertical face ---------------------------------------------------------- 11
Mudstone; pale-reddish-brown to mottled appearance resulting from scattered small green specks; forms gentle slopes ------------------- 26
Limestone, pale-gray ; includes black angular chert nodules; persistent
cliff former -------------------------------------------------------- 10
Mudstone, pale-reddish-brown; locally grades into siltstone; forms gentle slopes -------------------------------------------- 16
Limestone, light-gray, massive; includes black angular chert nodules; persistent cliff former --------------------------------------10
Mudstone, pale-red; locally altered to conglomeratic siltstone near top; lower part forms slopes, upper part stands as vertical face --- 33
Claystone, gray to purple, discontinuous; locally forms ledges ------- 1
Mudstone, reddish-brown; forms gentle slopes --------------------- 16
Limestone, light-gray: includes black angular chert nodules; weathers to form blocky masses--------------------------------------- 19

Total thickness: 166

Regions containing this locality

North America PlateTectonic Plate
Colorado Plateau, USAPlateau
Navajo Nation Indian Reservation, USAReservation
Hopi-Navajo Indian Reservations, Colorado Plateau, Apache; Navajo and San Juan Cos., Arizona & Utah, USA

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Regional Geology

This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.

Click on geological units on the map for more information. Click here to view full-screen map on

Early Jurassic - Late Triassic
174.1 - 237 Ma

ID: 3185972
Mesozoic sedimentary rocks

Age: Mesozoic (174.1 - 237 Ma)

Lithology: Sandstone-conglomerate

Reference: Chorlton, L.B. Generalized geology of the world: bedrock domains and major faults in GIS format: a small-scale world geology map with an extended geological attribute database. doi: 10.4095/223767. Geological Survey of Canada, Open File 5529. [154]

Norian - Carnian
208.5 - 237 Ma

ID: 2847322
Chinle Formation

Age: Late Triassic (208.5 - 237 Ma)

Stratigraphic Name: Chinle Formation

Description: Colorful mudstone, such as in the Painted Desert, and less abundant lenses of sandstone and conglomerate, deposited by a large river system. This unit typically is eroded into badlands topography and contains clays that are prone to shrinking and swelling. (210-230 Ma)

Comments: Original map source: Arizona Geological Survey, DI-8 Geologic Map of Arizona, Digital Spatial data for the Geologic Map of Arizona, v. 3.0, edited by S.M. Richard and S.M. Kneale, 2002, 10 p., 2 DOS HD disks. Arc/INFO export file (.e00) format, scale 1:1,000,000.

Lithology: Major:{mudstone}, Minor:{sandstone,conglomerate}

Reference: Horton, J.D., C.A. San Juan, and D.B. Stoeser. The State Geologic Map Compilation (SGMC) geodatabase of the conterminous United States. doi: 10.3133/ds1052. U.S. Geological Survey Data Series 1052. [133]

Data and map coding provided by, used under Creative Commons Attribution 4.0 License


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Witkind, I.J. & Thaden (1963), Geology and uranium-vanadium deposits of the Monument Valley area, Apache and Navajo Counties, Arizona, USGS Bulletin 1103: 30-31.

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