Marble, southeast Alaska

Unit symbol: Pzce
Age range early Permian to Devonian (419.2 to 272.3 Ma)
Lithology: Metamorphic
Group name: Marble
Ranges from dark-gray to white, purple, or tan partly recrystallized limestone to coarsely crystalline marble and dolostone (Redman and others, 1985; Gilbert and others, 1987; Gilbert, 1988). Unit may be sooty, thin-bedded to massive, and locally contains argillite, greenstone, and marble breccia. Exposed primarily in the northern part of southeast Alaska, unit is spatially associated with the Cheetdeekahyu group of Redman and others (1985) (unit |fw, here) and the Porcupine slate of Gilbert and others (1987) (unit ^Dps, here). Includes Paleozoic marble in the Glacier Bay area (D.A. Brew, written commun., 1997) and on Chichagof Island (Loney and others, 1963). S.M. Karl, (unpub. data) suggests that the marble on Chichagof Island is likely of Silurian age and possibly part of the Point Augusta Formation. Redman and others (1985) reported brachiopods of Mississippian to early Permian age and corals of Late Mississippian age, and Green and others (2003) reported Devonian conodonts from the same unit. Gilbert and others (1987) reported Mississippian and Devonian fossils for limestone associated with his Porcupine slate unit (MDm) and reported Triassic and Devonian fossils for the Glacier Creek volcanics of Redman and others (1985, their units uPzva, uPzvs, and uPzvb). The Triassic fossils, however, were most likely from Hyd Group limestone. In the southern part of southeast Alaska, in the Ketchikan region, a similar but unrelated marble is massive to platy, white, gray, and bluish gray, and weathers light-brown; it consists of a sugary to coarse-grained aggregate of calcite or dolomite and contains subordinate to minor amounts of muscovite, phlogopite, quartz, graphite, garnet, and pyrite (Berg and others, 1988). This marble contains relict fossils, thought to be crinoids, which suggest possible correlation of some marble lenses with the Permian crinoidal marble on Revillagigedo Island (unit TrMa). It is mapped in the Ketchikan and Prince Rupert quadrangles, where it is associated with the Kah Shakes sequence of Rubin and Saleeby, (1991) (unit Pzks here)

Source map information

Source map Karl, S.M., 2012, Unpublished data.
Symbol MDm
Unit name Marble
Description Medium bedded gray marble, locally fossiliferous. Mapped along south side of Klehini River, underlies Porcupine Slate
Lithology Metamorphic

Correlated geologic units

Label Pzm
Description Marble, Lower Permian to Devonian, northern southeast Alaska
Geologic age Devonian to Cisuralian
Geologic setting Metamorphic, undivided
Lithology Form Importance
Marble < Metacarbonate < Metasedimentary < Metamorphic Major
Limestone < Carbonate < Sedimentary Calcareous Minor