National Geochronological Database sample #5251

Outcrop or artificial surface exposure, Granite

Geographic location
-76.175, 39.733333
76° 10' 30" W, 39° 44' " N
Lancaster county, PA
Conowingo Dam 1:24,000 scale map quadrangle
Accurate to within 1 minute (~1 mile)
APPROX 0.7 MILE NORTH OF PENNSYLVANIA-MARYLAND STATE LINE
Source of sample Outcrop or artificial surface exposure
Rock name Granite
Description GRANITIZED PETERS CREEK FORMATION (MODERATE ALTERATION)
Laboratories Berkeley Geochronology Center
Compiler name Godoy, M.M.
Date compiled 1979 03
Precision of location Accurate to within 1 minute (~1 mile)
Location comment APPROX 0.7 MILE NORTH OF PENNSYLVANIA-MARYLAND STATE LINE
Bibliographic reference Lapham, D.M., and Bassett, W.A., 1964, K-Ar dating of rocks and tectonic events in the Piedmont of southeastern Pennsylvania: Geological Society of America Bulletin, v. 75, p. 661-668
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Geologic map unit -76.175, 39.733333
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K-Ar age determinations

Age estimate 360 ± 18Ma
Type of analysis conventional K-Ar
NO ANALYTICAL DATA GIVEN
Rock or mineral analyzed muscovite
Analytical details
Lab sample ID 15
Decay constants 4.83E-04, 0.585E-04
Comments AGE REFLECTS THE EFFECTS OF A REGIONAL THERMAL EVENT ABOUT 330 M.Y. AGO