Wrangell Lava

Unit symbol: Twv
Age range Tertiary, Pliocene to Oligocene (33.9 to 1.806 Ma)
Lithology: Igneous - Volcanic
Group name: Volcanic rocks, undivided
Consists of basaltic andesite, andesite, and dacite lava flows; andesitic lahar deposits and andesite to dacite porphyry, diorite, and quartz diorite. This is the older part of the Wrangell Lava in the McCarthy and Nabesna quadrangle, exposed on either side of the Totshunda Fault and in the adjacent Yukon. Includes the Sonya Creek and other Tertiary volcanic centers. Includes rhyolitic rocks, domes, hypabyssal, and plutonic rocks (Richter and others, 2006). K/Ar ages of volcanic rocks range between 26.3±0.8 and 8.8±0.9 Ma, whereas intruding plutons have K/Ar ages that range from 9.4±0.7 to 3.41±0.46 Ma

Source map information

Source map Richter, D.H., 1976, Geologic map of the Nabesna quadrangle, Alaska: U.S. Geological Survey Miscellaneous Geologic Investigations Map I-932, 1 sheet, scale 1:250,000.
Symbol Tp
Unit name Younger porphyry
Description Porphyries ranging from andesite to rhyodacite. Dikes and sills with alteration. Porphyries may represent hypabyssal equivalent of the older part of the Wrangell Lava
Lithology Igneous

Correlated geologic units

Label Twp
Description Wrangell Lava, hypabyssal and plutonic rocks
Geologic age Bartonian to Burdigalian
Geologic setting Extrusive
Lithology Form Importance
Hypabyssal-dacite < Felsic-hypabyssal < Hypabyssal < Igneous Dike or sill Major
Hypabyssal-andesite < Mafic-hypabyssal < Hypabyssal < Igneous Dike or sill Major