Jökull - 01.12.1990, Page 10
Figure 3. A simplified geologic map of the Hvalfjörðurregion with location of diamictite units (based on Arason
et al., 1974 Guðmundsson, 1976; Gunnlaugsson et al., 1972; Jónasson et al., 1973; Kristjánsson et al., 1980;
Sæmundsson, pers. comm. 1990). The numbers 1 to 10 refer to diamictite units. —Einfaldað jarðfrœðikort
af Hvalfirði og staðsetning seteininga (sett saman úr skýrslum eftir Arason o.fl., 1974; Guðmundsson, 1976;
Gunnlaugssono. fl., 1972; Jónasson o.fl., 1973; Kristjánsson o. fl., 1980; Sœmundsson.viðrœður 1990).
Table I. K/Ar age results for lavas on top of the mountain Akrafjall. —KIAr aldursákvörðun á hraunum efst úr
Akrafjalli.
Sample (Tr #) Weight (g) k2o (%) 40Ar*/gm (E-12) 40/36 (corr) 40 Ar* a (%) Age (Ma)(2 sigma)
FA51-1 5.0501 0.266 1.16077 321.7 8.4 3.12±0.23
(889) 0.250
0.258
FB01 3.2758 0.510 2.07501 314.7 6.28 2.87 ±0.23
(890) 0.493
0.502
a 40Ar* js tj,e radiogenic component of 40Ar. K measurements were made in duplicate on an IL 144 flame photometer using the
LÍBO5 fusion method. Argon measurements were made on a MS10 mass spectrometer at Case Westem Reserve University, in which the
Trap Current, Filament Current, Electrometer Voltage, Ion Repeller Voltage, Accelerating Voltage, Gain and Data Acquisition are controlled
by microprocessor. An input resistor of lxEIO Ohm was used throughout. The 40Ar/36Ar ratio measured for atmospheric argon, before
and after the analyses, yielded a value of 297.3 ±.03; all sample 40/36 (corr) values are corrected for the ideal atmospheric value of 295.5
40Ar/36Ar.
8 JÖKULL, No. 40, 1990