Geologic Map of Alaska: Slana Spur and Station Creek Formations and Tetelna Volcanics

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	PIPsl
Unit name	Slana Spur Formation -- Volcaniclastic rocks member
Description	Dark-gray, dark-green, and maroon volcanic and volcaniclastic rocks. Chiefly volcanic flows interbedded with lapilli tuff, volcanic breccia, graywacke, argillite, and limestone to marble. Local massive to bedded conglomerate, graywacke, and siltstone. Metamorphosed to lower greenschist facies.
Lithology	Metamorphic

Correlated geologic units

Label	Pzv
Description	Slana Spur Formation, volcaniclastic rocks, Early Permian-Middle Penn. [equivalent to part of Station Creek Fm.]
Geologic age	Pennsylvanian to Cisuralian
Geologic setting	Extrusive

Lithology	Form	Importance
Mafic-volcanic < Volcanic < Igneous	Volcaniclastic	Indeterminate, major
Mafic-volcanic < Volcanic < Igneous	Flow	Indeterminate, major
Greenstone < Metaigneous < Metamorphic		Indeterminate, major
Phyllite < Metaclastic < Metasedimentary < Metamorphic	Zeolitic (prehnite-pumpellyite)	Indeterminate, major
Conglomerate < Clastic < Sedimentary	Bed	Indeterminate, major
Marble < Metacarbonate < Metasedimentary < Metamorphic	Zeolitic (prehnite-pumpellyite)	Minor
Mudstone < Clastic < Sedimentary	Bed	Minor