Náttúrufræðingurinn - 1989, Blaðsíða 22

threshold for late Tertiary sediments. The
sheet is clearly a potential heat source.
Carbon isotope analyses (Table 5) on one
asphalt sample and a lignite sample show
values which are typical for terrestrial or-
ganic material of late Tertiary to Quater-
nary age. The carbon isotope data do not
contradict the hypothesis that the lignite is
the source rock of the asphalt. Finally, a
maturation analysis was performed on
three lignite samples taken close to the
sheet. The samples show high vitrinite re-
flectance values (2.4—3.18%), implying the
samples are well within the dry gas zone,
which does not contradict the idea, that
the oil generated from the lignite. There-
fore, it is concluded that the asphalt in all
probability originated in the lignite seam
and that the formation of the oil was due
to short term local heating from the
igenous sheet estimated to have taken
place 3 mill. years ago.
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