Slana Spur and Station Creek Formations and Tetelna Volcanics

Unit symbol: PIPt
Age range lower Permian to Middle Pennsylvanian (323.2 to 272.3 Ma)
Lithology: Sedimentary
Group name: Skolai and Mankomen Groups, undivided
Lower volcanic section chiefly submarine andesite and basalt flows, locally pillowed and brecciated; upper volcaniclastic section generally grades upward from coarse volcanic breccia to abundant volcanic graywacke and finally to volcanic lutite. No fossils are known in the type area. Age assignment is constrained by overlying Hasen Creek Formation (unit Peh) and stratigraphic and lithologic correlation with the Slana Spur Formation (Nokleberg and others, 1992a). As here mapped, includes units Pzt and IPt (Tetelna Volcanics) of Nokleberg and others (1992a). Unit Pzt of Nokleberg and others (1992a) consists of andesitic flows, mud and debris avalanches, and aquagene tuff interbedded with fine- to coarse-grained volcaniclastic rocks; this unit has yielded fragments of late Paleozoic bryozoans. The Tetelna Volcanics is similar, and consists chiefly of dark-green, dark-gray-green, and purplish-gray-green volcanic flows, locally graded mud and debris avalanches, and lapilli-pumice tuff interbedded with fine- to coarse-grained volcaniclastic rocks. In the Talkeetna Mountains quadrangle, Permian conodonts were collected from unit Pzv (Csejtey and others, 1978). Metamorphosed to lower greenschist facies. As here mapped, unit also includes greenstone of the Skolai Group in the Valdez quadrangle (Winkler and others, 1981) and early Permian(?) and Pennsylvanian andesitic volcanic rocks in the Healy quadrangle (Csejtey and others, 1992). Locally, may also include rocks that could be assigned to the Nikolai Greenstone (Trn) following more detailed mapping (J.M. Schmidt, written commun., 2007)

Source map information

Source map Nokleberg, W.J., Aleinikoff, J.N., Lange, I.M., Silva, S.R., Miyaoka, R.T., Schwab, C.E., and Zehner, R.E., with contribution for selected areas from Bond, G.C., Richter, D.H., Smith, T.E., and Stout, J.H., 1992, Preliminary geologic map of the Mount Hayes quadrangle, eastern Alaska Range, Alaska: U.S. Geological Survey Open File Report 92-594, scale 1:250,000 [Received as CAD coverage produced in 1996].
Symbol Pzt
Unit name Aquagene tuff, argillite, limestone, chert, andesite tuff, and greenstone
Description Chiefly andesite flows, mud and debris avalanche deposits, and tuff interbedded with fine- to coarse grained volcaniclastic rocks. Contains lesser interlayered basaltic aquagene tuff, gray-green andesite tuff, gray-green basalt, dark-gray siliceous argillite, light-gray to white calcite, limestone, and marble, and red and black chert. Unit generally granoblastic, locally weakly schistose; metamorphosed to lower greenschist facies.
Lithology Metamorphic

Correlated geologic units

Label IPt
Description Station Creek Formation andesitic volcanic rocks (correlated with Tetelna volcanics), Early Permian? and Pennsylvanian
Geologic age Pennsylvanian to Cisuralian
Geologic setting Extrusive
Lithology Form Importance
Andesite < Mafic-volcanic < Volcanic < Igneous Flow Major
Andesite < Mafic-volcanic < Volcanic < Igneous Volcaniclastic Minor