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Source map Karl, S.M., 2012, Unpublished data.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 MDcp
Unit name Carbonaceous phyllite
Description Black argillite in Tsirku River area, Skagway quadrangle. On Admiralty and Kupreanof Islands includes black, carbonaceous phyllite, with subordinate metagraywacke, greenstone, or marble. Phyllite contains graphite, chlorite, and pyrite. Greenstone is recrystallized to plagioclase, actinolite, chlorite, epidote, and calcite, sometimes with relict augite. In Saginaw Bay includes black chert member of the Saginaw Bay Formation, consisting of thin-bedded black chert and minor thin-bedded dense dark gray limestone (Muffler, 1967). With lenses of marble. Stratigraphically adjacent to or above Devonian Gambier Bay Formation. No fossils recovered. Black chert member of the Saginaw Bay Formation overlies Devonian volcanic member of the Saginaw Bay Formation. Black chert member limestone beds contain late Eifelian conodonts Tortodus kockelianus kockelianus (Bischoff and Ziegler), pb elements of Oulodus sp., pa element of Polygnathus aff. P. pseudofoliatus Wittekindt, and late Emsian to early Frasnian Polygnathus linguiformis linguiformis (A. G. Harris in www.alaskafossil.org). Inferred stratigraphic position and lithology correlate with black massive siltstone and marble of the Kaskawulsh Group.
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