Kulthieth Formation

Unit symbol: Tkf
Age range Tertiary, Eocene (56 to 33.9 Ma)
Lithology: Sedimentary
Group name: Sedimentary rocks of eastern Prince William Sound
Exposed in eastern Prince William Sound, unit consists of mostly fluvial and lacustrine deposits and local debris flow deposits and some shallow marine deposits. Unit contains at least 3,000 m of orange-weathering, light-gray feldspathic to lithofeldspathic sandstone and calcareous sandstone interbedded with dark-gray siltstone, pebble conglomerate, and many thin beds of coal. Commonly well-indurated with bituminous coal. “Sandstone to shale ratios in measured sections of the Kulthieth Formation (Martin, 1908) average about 1:1. Sandstone varies from massive intervals as much as 150 m thick to thin-bedded and shaly intervals. Bituminous to semi-anthracite coal in beds as much as 3 m thick is conspicuous, but minor part of sequence. Commonly intensely deformed into imbricated stacks of fault-bounded chevron folds displaying shearing and structural thinning and thickening of coal beds” (Winkler and Plafker, 1993). Bedding plane thrusts tend to be localized in coal beds (George Plafker, written commun., 2003). Sparse warm-water marine molluscan megafauna and locally abundant subtropical plant fossils are present; unit has minor tongues of transitional marine strata lithologically similar to the underlying Stillwater Formation and overlying Tokun Formation (Nelson and others, 1985). Age control derived from widespread fossil plant collections and a single mollusk collection near the top of the section (Winkler and Plafker, 1981). Mollusks indicate a late Eocene age, whereas fossil plant collections indicate wider range, from late middle Eocene to early Oligocene (Winkler and Plafker, 1981; Wolfe, 1977), but the widely accepted age for the unit is Eocene

Source map information

Source map Winkler, G.R., and Plafker, George, 1993, Geologic map of the Cordova and Middleton Island quadrangles, southern Alaska: U.S. Geological Survey Miscellaneous Investigations Map I-1984, 1 sheet, scale 1:250,000.
Symbol Tk
Unit name Kulthieth Formation
Description Includes at least 1,500 m of interbedded, massive to thin-bedded, coal-bearing arkosic sandstone, dark-gray to black carbonaceous siltstone and shale, and minor coal. Commonly intensely deformed into imbricated stacks of fault-bounded chevron folds.
Lithology Sedimentary

Correlated geologic units

Label Tak
Description Amphithreatre (Canada) and Kulthieth, mostly fluvial and lacustrine deposits, local debris-flow deposits; some shallow marine
Geologic age Eocene
Geologic setting Sedimentary, continental
Lithology Form Importance
Conglomerate-mudstone < Mixed-clastic < Clastic < Sedimentary Bed Major