Rit (Vísindafélag Íslendinga) - 01.06.1976, Side 166

The water from the well at Siglufjörður (sample No. 178) also
has a 5D-value, 5n = — 77%0, similar to present-day precipitation in
the nearest mountains north of the well. The same is also the case
for the thermal water in Ólafsfjörður (samples No. 182—184).
Consequently the thermal water observed on the northemmost
part on the Tröllaskagi peninsula seems to be local precipitation
derived from the nearest mountainous area.
The origin of the thermal water in Svarfaðardalur (samples No.
185 and 186), with 8n = — 91.5%0 and ðD = — 103.7%0 respectively,
and Hrísey (sample No. 196), with ðD = — 91.3%0, on the other
hand, seems more questionable. It may well be possible that this
water and conceivably also the water at Laugaland (sample No.
195), with 8D = — 100.0%0, originates in the highest mountainous
part of Tröllaskagi. This water, however, may also be derived from
the same deep groundwater stream that feeds the hot springs in
the inner part of the valley Eyjafjörður.
15. 16 Eyjafjörður and Fnjóskadalur.
This area includes the thermal water in the valleys Eyjafjörður
(see Fig. 40, samples No. 189—195 and No. 197—199), Fnjóskadalur
(samples No. 200 and 202) and Stóru-Tjamir (sample No. 201).
Although Fnjóskadalur and Stóru-Tjarnir belong to the district S-
Þingeyjarsýsla (see section 15.18), these places are discussed here
because they are located outside the neo-volcanic zone.
In these areas the situation seems to be similar to that in Skaga-
fjörður. The lowest 8D-value in Eyjafjörður, 8D = — 107%0, is ap-
proximately as low as those found in Skagafjörður, hut the 8D-value
varies from — 92%0 til — 107%0 within the area, either due to mix-
ing of deep water with more local groundwater or to different origin
or age of the water.
Thus deuterium measurements seem to indicate that the thermal
water in Eyjafjörður is derived from a deep groundwater flow that
originates in central Iceland but flows to the north along the valley
and possibly further north under the bed of the ocean. A similar
flow model also accounts for the hot springs in Fnjóskadalur and at
Stóru-Tjarnir.
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