Kayak Shale

Unit symbol: Mk
Age range Mississippian (358.9 to 323.2 Ma)
Lithology: Sedimentary
Group name: Kayak Shale (Endicott Group)
Widely exposed across northern Alaska, the Kayak Shale is commonly the uppermost exposed unit of the Endicott Group. It consists of dark-gray to black fissile clay shale with yellowish-brown-weathering thin fossiliferous limestone beds near top. Commonly contains conspicuous reddish-brown-weathering nodules; lower part contains thin interbeds of gray and brown, irregularly bedded fine- to medium-grained, impure, partly worm-burrowed sandstone near base. Unit disconformably overlies the Kanayut Conglomerate (unit MDegk) in its type area and the central Brooks Range and the Neruokpuk (unit CPxwn) in northeast Alaska. It is complexly deformed by isoclinal folding and shearing; its lower contact is commonly a thrust fault; it acted as a detachment zone for the overlying Lisburne. Thickness is probably more than 500 m (Brosgé and others, 1976, 1979; Mull and others, 1994). Bioclastic limestone beds are generally less than 1.8 m thick and are reddish- and yellowish-brown-weathering fossil hash. Crinoids, brachiopods, bryozoan, and corals are locally abundant (Kelley, 1990a). Siderite concretions are characteristic in places. Locally contains felsic to intermediate intrusive, extrusive, and volcaniclastic rocks (Dover and others, 2004), as well as red- and green-weathering slaty phyllite and argillite and minor semischistose quartz-rich siltstone and marble (Nelson and Grybeck, 1980)

Source map information

Source map Dover, J.H., Tailleur, I.L., and Dumoulin, J.A., 2005, Unpublished data.
Symbol Mi
Unit name Isikut unit of Mull and Werdon (1994) - Endicott, sequence, Endicott group, Aniuk River facies
Description Reddish-tan to grayish-green, tan- to reddish-brown-weathering, thin- bedded to platy siltstone and phyllitic shale; bioturbation and flaser structure common. Locally contains quartzitic sandstone interbeds at the base and thin, sandy limestone interbeds higher in the section. Includes some interbeds typical of the Kayak Shale. Minimum thickness about 200 m. Pervasively folded; typically displays prominent axial-plane cleavage.
Lithology Sedimentary

Correlated geologic units

Label Mk
Description Endicott Group, Kayak Shale
Geologic age Mississippian to Visean
Geologic setting Sedimentary, slope-and-deep-water
Lithology Form Importance
Shale < Mudstone < Clastic < Sedimentary Bed Major
Phyllite < Metaclastic < Metasedimentary < Metamorphic Indeterminate, major
Limestone < Carbonate < Sedimentary Bed Incidental