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 QTw
Unit name Wrangell Lava (older part)
Description Undivided andesite and basaltic andesite flows, dacite flows and dacite domes, tuffs and breccias, and dacitic andesite agglutinate flows.
Lithology Igneous

Correlated geologic units

Label Twl
Description Wrangell Lava, Pliocene to Oligocene lower part, undivided
Geologic age Late-Oligocene to Pliocene
Geologic setting Extrusive
Lithology Form Importance
Hypabyssal-andesite < Mafic-hypabyssal < Hypabyssal < Igneous Dome Major
Basalt < Mafic-volcanic < Volcanic < Igneous Dome Major
Volcanic < Igneous Flow Indeterminate, major
Andesite < Mafic-volcanic < Volcanic < Igneous Flow Indeterminate, major
Volcanic < Igneous Pyroclastic Minor
Basalt < Mafic-volcanic < Volcanic < Igneous Flow Minor
Dacite < Felsic-volcanic < Volcanic < Igneous Flow Incidental