Metasedimentary rocks of Bluecloud Mountain

Unit symbol: PzPxb
Age range early Paleozoic to Proterozoic? (1000 to 485.4 Ma)
Lithology: Metamorphic
Group name: Metasedimentary and metavolcanic rocks of the Central Belt and Northern Thrust assemblage of Till and others (2008a)
Light- to dark-gray phyllite, dark-gray to black metaquartzite, dark-gray and grayish-brown calcareous phyllite, and reddish-brown-weathering impure marble exposed in fault-bounded lenses along the Schist belt-Central belt contact in the Wiseman quadrangle, as described by Till and others (2008a). Lithologic layering is visible in outcrop where it crosses foliation; locally, lithologic layering is transposed by foliation, which is defined by fine-grained mica. In thin section, lithologic layering and relict clasts are recognizable; metamorphic minerals include white mica, chlorite, stilpnomelane(?), and very fine-grained garnet or albite. No protolith age control is available; the protolith may have been a sequence of turbidites (Till and others, 2008a)

Source map information

Source map Dillon, J.T., Brosge, W.P., and Dutro, J.T., Jr., 1986, Generalized geologic map of the Wiseman quadrangle, Alaska: U.S. Geological Survey Open-File Report 86-219, 1 sheet, scale 1:250,000.
Symbol Dhs
Unit name Hunt Fork Schist
Description Twice metamorphosed sedimentary and volcanic rocks; middle to upper Greenschist facies. Metamorphic facies and texture increases southward; mostly phyllite and limestone in north; schist and marble in south. Lower Endicott Group- Carbonaceous siliceous clastic rocks. Grades downward into Beaucoup Formation in some places; unconformably overlies upper Middle Devonian and older rocks in other places. Black quartz schist and biotite garnet quartz schist.
Lithology Metamorphic

Correlated geologic units

Label PzZb
Description Metasedimentary rocks of Bluecloud Mountain, gray phyllite, dark-gray to black metaquartzite, calcareous phyllite, and impure marble
Geologic age Neoproterozoic to Devonian
Geologic setting Sedimentary, undivided
Lithology Form Importance
Phyllite < Metaclastic < Metasedimentary < Metamorphic Major
Quartzite < Metaclastic < Metasedimentary < Metamorphic Major
Marble < Metacarbonate < Metasedimentary < Metamorphic Minor