Marble of the Brooks Range

Unit symbol: Pzm
Age range Devonian and older (541 to 358.9 Ma)
Lithology: Metamorphic
Group name: Marble
As described by Till and others (2008a), unit consists of “white to gray (less commonly black), fine to coarsely crystalline, massive to platy marble and subordinate metalimestone and dolostone occurs discontinuously in all quadrangles within the map area. |m locally contains abundant disseminated quartz or mica grains, and (or) interlayers of schist, quartzite, or phyllite. In some areas, these strata contain no relict sedimentary textures and few or no fossils; elsewhere, relict sedimentary structures and fossils occur, but rocks have not been studied in sufficient detail to allow assignment to * * *” other better defined carbonate units of Devonian and older age. “Existing fossil data and regional relationships suggest that most |m is Cambrian through Mississippian in age” (Till and others, 2008a). As shown here, unit includes exposures in the Ambler River, Survey Pass, Wiseman, Chandalar, Philip Smith Mountains, Christian, and Arctic quadrangles that were traditionally assigned to the Skajit Limestone of Baird Group, a formal unit not used herein. It excludes part of unit Pzm of Till and others (2008a) in the Baird Mountains quadrangle, which is here included in unit Pzcn

Source map information

Source map Brosge', W.P., Reiser, H.N., Dutro, J.T., Jr., and Detterman, R.L., 1979, Bedrock geologic map of the Phillip Smith Mountains quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-879-B, 2 sheets, scale 1:250,000.
Symbol DSs
Unit name Skajit Limestone
Description Gray weathering, light to dark gray limestone and dolomite, mostly recrystallized or with slatey cleavage; rare chert nodules. In southeast part of quadrangle top beds partly replaced by massive or brecciated black recrystallized chert in discontinuous layer 1 - 10 meters thick that commonly contains pyrite and other sulfides. Marine
Lithology Sedimentary

Correlated geologic units

Label DSbs
Description Baird Group, Skajit Limestone
Geologic age Middle-Cambrian to Devonian
Geologic setting Sedimentary, carbonate
Lithology Form Importance
Dolostone < Carbonate < Sedimentary Bed Major
Limestone < Carbonate < Sedimentary Bed Major
Marble < Metacarbonate < Metasedimentary < Metamorphic Greenschist Indeterminate, major
Schist < Metamorphic Greenschist Incidental