Porcupine slate of Redman and others (1985)

Unit symbol: Pzps
Age range late Paleozoic (419.2 to 252.2 Ma)
Lithology: Metamorphic
Group name: Cannery Formation and Porcupine slate of Redman and others (1985), undivided
Limonite-stained black slate and dark-gray phyllite with subordinate black argillite and banded siltstone in the Skagway quadrangle (Gilbert and others, 1987). As originally described, includes gray bioclastic limestone and marble, but we show those rocks as part of unit |ce herein. The Porcupine slate of Redman and others (1985) intertongues with rocks mapped here as part of the Hyd Group (unit ^hg) and, because of locally intense deformation, in many places workers could not distinguish a difference between the Porcupine slate, older rocks, and the Hyd Group (Green and others, 2003). The Porcupine slate contains Devonian to Triassic fossils and locally overlies marble (unit Pzce, here) that contains Devonian to Mississippian fossils (Gilbert and others, 1987). We suggest, however, that the Triassic fossils are more likely associated with the interleaved Hyd Group. The Porcupine slate has been correlated with the Cannery Formation (unit PDcf) (Karl and others, 2010)

Source map information

Source map Redman, E.C., Gilbert, W.G., Jones, B.K., Rosenkrans, D.S., and Hickok, B.D., 1985, Preliminary bedrock-geologic map of the Skagway B-4 quadrangle: Alaska Division of Geological and Geophysical Surveys Report of Investigations 85-6, 1 sheet, scale 1:40,000.
Symbol uPzs
Unit name Porcupine slate
Description Black slate and phyllite, with banded siltstone, graywacke, chert, limestone, conglomerate, and volcanic layers. Gradational below Glacier Creek units and above marble limestone unit. Porcupine Creek area.
Lithology Metamorphic

Correlated geologic units

Label TrDps
Description Porcupine slate of southeast Alaska (uPzs, SK004)
Geologic age Devonian to Triassic
Geologic setting Sedimentary, marine, shallow to deep association, undivided
Lithology Form Importance
Slate < Metaclastic < Metasedimentary < Metamorphic Major
Argillite < Metaclastic < Metasedimentary < Metamorphic Indeterminate, major
Phyllite < Metaclastic < Metasedimentary < Metamorphic Indeterminate, major
Marble < Metacarbonate < Metasedimentary < Metamorphic Minor
Chert < Chemical < Sedimentary Bed Minor
Limestone < Carbonate < Sedimentary Calcareous Incidental
Conglomerate < Clastic < Sedimentary Bed Incidental
Graywacke < Sandstone < Clastic < Sedimentary Bed Incidental