Geology Reference
In-Depth Information
Table 7. 5.
Isotopic and geochemical composition of water (ice) in mg/L at two drained lake sites
in the Mackenzie Delta region, Canada. Site 1: lake drained about 150 years ago, permafrost is
20-35 m thick. Site 2: lake drained between 1935 and 1950, permafrost is 15-20 m thick.
Site 1
Site 2
Surface water
Permafrost
Sub-permafrost
Surface
Sub-permafrost
(residual lake)
(at 20.5 m)
water (at 21.5 m)
water
water (at 17 m)
δ
H
2
18
0(in ‰)
−
21.6
−
16.2
−
28.8
−
19.7
−
27.7
(at 14.5 m)
Specifi c
188
190
1224
134
1714
conductance
(
mho\cm)
Chloride
µ
16
-
106
18
141
Magnesium
7
2.3
49
4
148
Potassium
2.4
2
5.6
1.5
7.3
Calcium
14
17
93
10
54
Sodium
2
4
83
9
92
Source: Mackay and Lavkulich (1974).
Table 7.6.
Ty p i c a l
O
18
values reported from different ground ice types in western Arctic
Canada and Siberia, together with typical values of basal meltwater/regelation ice from Svalbard
and the Swiss Alps.
δ
δ
0
18
Reference
Basal meltwater/regelation ice:
Tranfeuron Glacier, Swiss Alps
−
10 to
−
15‰
Lemmens et al. (1982)
Gruve 7, Adventdalen, Svalbard
−
15‰
Christiansen et al. (2005)
Longyearbreen, Svalbard
−
12‰
O. Humlum (pers. communication)
Ground ice:
Massive ice
−
28 to
−
35‰
Mackay (1983b)
Buried glacier ice
−
26 to
−
35‰
Lorrain & Demeur (1985)
French & Harry (1990)
Modern ice wedges:
−
22 to
−
26‰
Mackay (1983b), Michel (1990),
Lauriol et al. (1995)
Late-Pleistocene ice wedges:
−
28 to
−
34‰
Mackay (1983b)
Va si l'chuck a nd Va si l'chuck (19 9 7)
that signifi cant fractionation has occurred during freezing. The values for surface water
compare favorably with annual SMOW values.
δ
O
18
values are useful not only in inferring thaw unconformities but, because different
ground-ice types have different isotopic signatures, can characterize ground-ice bodies.
For example, Table 7.6 provides typical
O
18
isotope values for massive ground ice of
intra-sedimental origin, massive icy sediments of presumed buried glacier-ice origin,
modern and Pleistocene-age ice wedges, and basal meltwater/regelation ice.
Tritium (H
3
) is a radioactive isotope of modern age with a short half-life (12.43 years).
Its detection in the upper layers of permafrost, in the active layer, and in seasonal ice
δ
