National Geochronological Database sample #16531

Outcrop or artificial surface exposure, Hornblende andesite porphyry

Geographic location
-157.483333, 56.633333
157° 29' " W, 56° 38' " N
Sutwik Island C-5 1:63,360 scale map quadrangle
Accurate to within 0.1 minute (~500 feet)
eastern Cape Kumlik
Source of sample Outcrop or artificial surface exposure
Rock name Hornblende andesite porphyry
Description altered
Laboratories USGS Menlo Park
Compiler name Moscati, R.
Date compiled 1992 04
Precision of location Accurate to within 0.1 minute (~500 feet)
Location comment eastern Cape Kumlik
Bibliographic reference Wilson, F.H., 1978, Map showing preliminary results of K-Ar studies in the Chignik and Sutwik Island quadrangles, Alaska: U.S. Geologica Survey Open File Report 78-1064.
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Geologic map unit -157.483333, 56.633333
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K-Ar age determinations

Age estimate 34.95 ± 10Ma
age of intrusion
Rock or mineral analyzed hornblende
Analytical details
Lab sample ID 77AWs 40
Decay constants 4.962E-04, 0.581E-04, 1.1167E-04
K2O concentration 0.467 %
Radiogenic 40Ar concentration 0.2372
Radiogenic Ar 30 %