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 MacKevett, Jr., E.M., 1978, Geologic map of the McCarthy quadrangle, Alaska: U.S. Geological Survey Miscellaneous Investigations Series Map I-1032, 1 sheet, scale 1:250,000.
Symbol Th
Unit name Hypabyssal rocks
Description Dacite, andesite, and rhyodacite porphyry. Typically strongly porphyritic. Correlates with younger porphyry of Nabesna quadrangle and with hypabyssal rocks associated with the Wrangell Lava in Alaska and Canada
Lithology Igneous

Correlated geologic units

Label Twd
Description Wrangell Lava, dome and hypabyssal rocks
Geologic age Pliocene
Geologic setting Extrusive
Lithology Form Importance
Hypabyssal-dacite < Felsic-hypabyssal < Hypabyssal < Igneous Dome Indeterminate, major
Hypabyssal-dacite < Felsic-hypabyssal < Hypabyssal < Igneous Dome Indeterminate, major
Hypabyssal-rhyolite < Felsic-hypabyssal < Hypabyssal < Igneous Dome Indeterminate, major
Andesite < Mafic-volcanic < Volcanic < Igneous Dome Minor