Paradise Fork Formation and correlative units

Unit symbol: DSpf
Age range Lower Devonian and Silurian (443.4 to 393.3 Ma)
Lithology: Sedimentary
Group name: Farewell basinal facies carbonate rocks
“Deep-water turbiditic and hemipelagic deposits of dark, thin-bedded, fissile to laminated limestone, limy shale, and siltstone. The formation has an abundant graptolite, conodont, and ostracode fauna. It was originally assigned an Early to Late Silurian age by Dutro and Patton (1982), but subsequent investigations by Dumoulin and others (1997) indicate that it ranges from Silurian to Early Devonian” (Patton and others, 2009). The type area of the Paradise Fork Formation is in the Medfra quadrangle, and similar rocks are present in the Taylor Mountains quadrangle (Blodgett and Wilson, 2001) and in the Lime Hills, Talkeetna, and McGrath quadrangles (Wilson and others, 1998). In the Taylor Mountains quadrangle, unit is primarily thin- to medium-bedded, laminated, dark-gray to dark-brown, platy lime mudstone, and has a strong petroliferous odor (Blodgett and Wilson, 2001). Coarse-grained limestone debris-flow deposits that have clasts of algal boundstone reef material are common in uppermost part of the unit (Blodgett and Wilson, 2001). In the Talkeetna quadrangle, unit includes Silurian limestone mapped by Reed and Nelson (1980) that consists of light-gray to light-brown, massive-weathering metalimestone and local thin-bedded to laminated limestone

Source map information

Source map Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, 2009, Geologic map of the Yukon-Koyukuk basin, Alaska: U.S. Geological Survey Scientific Investigations Map SIM-2909, 26 p., 2 sheets, scale 1:500,000.
Symbol DSp
Unit name Paradise Fork Formation
Description Deep-water turbiditic and hemipelagic deposits of dark, thin-bedded, fissile to laminated limestone, limy shale, and siltstone. The formation has an abundant graptolite, conodont, and ostracod fauna. It was originally assigned an Early to Late Silurian age by Dutro and Patton (1982), but subsequent investigations by Dumoulin and others (1997) indicate that it ranges from Silurian to Early Devonian
Lithology Sedimentary

Correlated geologic units

Label Spf
Description Paradise Fork Formation and correlative units
Geologic age Llandovery to Wenlock
Geologic setting Sedimentary, slope-and-deep-water
Lithology Form Importance
Limestone < Carbonate < Sedimentary Bed Major
Shale < Mudstone < Clastic < Sedimentary Calcareous Minor