Volcanic member

Unit symbol: Trsyv
Age range Upper Triassic (235 to 201.3 Ma)
Lithology: Sedimentary
Group name: Shuyak Formation, undivided
Tholeiitic vesicular pillow greenstone; locally contains beds of pillow-breccia agglomerate, tuff, and argillite (Connelly and Moore, 1979). Also includes diabasic bodies intruding Shuyak Formation on west side of Shuyak Island that do not have visible thermal aureoles (Connelly and Moore, 1979)

Source map information

Source map Connelly, William, and Moore, J.C., 1979, Geologic map of the northwest side of the Kodiak and adjacent islands, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-1057, 2 sheets, scale 1:250,000.
Symbol Trsv
Unit name Shuyak Formation, volcanic member
Description Vesicular pillowed greenstone, locally containing beds of pillow breccia agglomerate, tuff, and argillite. Greenstone is tholeiitic in composition.
Lithology Igneous

Correlated geologic units

Label Trsv
Description Shuyak Formation, volcanic member
Geologic age Late-Triassic
Geologic setting Extrusive
Lithology Form Importance
Greenstone < Metaigneous < Metamorphic Major
Mafic-volcanic < Volcanic < Igneous Flow, pillows Indeterminate, major
Mafic-volcanic < Volcanic < Igneous Pyroclastic, tuff Indeterminate, major
Argillite < Metaclastic < Metasedimentary < Metamorphic Indeterminate, major