Calico Bluff and Ford Lake Shale, undivided

Unit symbol: IPDcf
Age range Lower Pennsylvanian to Devonian (419.2 to 315.2 Ma)
Lithology: Sedimentary
Group name: Calico Bluff and Ford Lake Shale, undivided
Calico Bluff Formation consists of rhythmically interbedded, dark-brownish-gray and brownish-black limestone and shale, and laminated siliceous shale and chert. Its thickness is about 450 m. Ford Lake Shale is “* * * predominantly grayish-black siliceous shale and laminated grayish-black chert. Brownish-black phosphate concretions, some as large as 4 inches (10 cm) in maximum dimension and very pale orange carbonate concretions a few feet (~1 m) in length are common. Several limestone and dolomite beds and lenses occur in the upper part of the formation” (Brabb, 1969). Ford Lake Shale is about 600 m thick and grades upward to Calico Bluff Formation. Calico Bluff Formation is equivalent to Hart River Formation of the Yukon and is Late Mississippian to Early Pennsylvanian in age, whereas Ford Lake Shale is Late Devonian to Late Mississippian in age. Unit is restricted to the Charley River and northeast Eagle quadrangles

Source map information


Correlated geologic units

Label IPMcb
Description Calico Bluff Formation
Geologic age Late-Mississippian to Early-Pennsylvanian
Geologic setting Sedimentary, undivided
Lithology Form Importance
Limestone < Carbonate < Sedimentary Bed Major
Shale < Mudstone < Clastic < Sedimentary Bed Major