Geologic mapping and potassium-argon dating by R. L. Detterman, F. H. Wilson, J. E. Case, and Nora Shew in the Ugashik and western part of the Karluk quadrangles have shown that the Eocene and Oligocene volcanic arc continues into these quadrangles from the south in the Chignik and Sutwik Island quadrangles. Surface exposures of the arc extend northward to approximately 57°30'N., or midway through the Ugashik quadrangle, but none are observed north of that point. Subsurface drill-hole data (Brockway and others, 1975) indicate continuation of the arc, possibly offset to the northwest of the northernmost known surface exposures.
In the extreme northern part of the Ugashik and Karluk quadrangles, volcanic rocks again become important. These volcanic rocks are as yet undated; however, they may be related to the Katmai late Tertiary volcanic centers.
Like the early Tertiary volcanic arc, the present-day Aleutian arc is also offset to the northwest in the northern part of the Ugashik and Karluk quadrangles. No major offset of the Mesozoic rocks is indicated through the offset zone; this fact suggests a change in the Tertiary tectonic regime in the area of the offset.
Additional publication details
|Publication Subtype||USGS Numbered Series|
|Title||Offset of Tertiary arcs on the Alaska Peninsula: A section in Geological Survey research, fiscal year 1981|
|Series title||Professional Paper|
|Publisher||U.S. Government Printing Office|
|Publisher location||Washington, D.C.|
|Contributing office(s)||Alaska Science Center|
|Larger Work Type||Report|
|Larger Work Subtype||USGS Numbered Series|
|Larger Work Title||Geological Survey research, fiscal year 1981 (Professional Paper 1375)|
|Other Geospatial||Alaska Peninsula, Karluk quadrangle, Ugashik quadrangle|
|Google Analytic Metrics||Metrics page|