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

Correlated geologic units

Label Trvm
Description Mafic dikes, sills, and plugs intruding Shuyak Formation
Geologic age Late-Triassic
Geologic setting Extrusive
Lithology Form Importance
Gabbro < Gabbroic < Plutonic < Igneous Diabase Major