Geology Reference
In-Depth Information
7.6.3. Buried Glacier Ice
Notwithstanding the previous conclusion, it is probable that certain bodies of massive
ice and icy sediments are of buried glacier-ice origin. This hypothesis was initially
suggested by Russian Quaternary geologists (Astakhov and Isayeva, 1988; Kaplanskaya
and Tarnogradskiy, 1986). Terms such as “ice/sediment complex,” “sheet-ice complex,”
and “deposit-forming ice” are used to describe these icy sediments.
Several studies in the western Canadian arctic suggest that at least some massive icy
bodies may also be buried basal glacier ice (Dallimore and Wolfe, 1988; French and Harry,
1988, 1990; Lorrain and Demeur, 1985). Several lines of evidence support the buried-
glacier ice mechanism: (1) deformation structures and folds of varying dimensions and
intensities are typical of glacier ice; (2) sediment-rich layers often resemble shear planes
(Rampton and Walcott, 1974); (3) there is a range of grain and clast sizes contained within
the massive ice and icy bodies, from clay to pebbles to striated boulders; and (4) the
overlying soil-ice contact is often unconformable. It should also be pointed out that many
massive icy bodies in both Siberia and northern Canada that have been ascribed a glacial
origin occur in regions that were glaciated during the Pleistocene.
Recent stratigraphic investigations provide further support for a buried glacier ice
hypothesis. For example, at two locations in the Tuktoyaktuk Coastlands, features char-
acteristic of both basal glacier ice and intra-sedimental ice occur (Murton et al., 2004,
2005). The basal-ice features include (a) ice facies and ice-crystal fabrics similar to basal
ice in contemporary glaciers and ice-cored moraines, (b) an erosional unconformity that
truncates the top of the massive icy bodies, and (c) a covering of glacigenic or aeolian
sediment. A similar interpretation has been proposed for massive icy sediments in the
Kara Sea region of northern Russia. There, it is hypothesized that relict glacier ice, buried
in sediment and incorporated within permafrost, may survive for many tens of thousands
of years and even several interglacial and stadial events (Henricksen et al., 2003; Lokrantz
et al., 2003).
7.6.4. Other Mechanisms
In addition to the two main hypotheses discussed above, several others have also been
proposed. For example, K. Fujino et al. (1983, 1988) concluded that the massive ground
ice at Peninsula Point near Tuktoyaktuk, Canada, was regelation ice formed from the
episodic inundation of a perennial snow bank. However, none of the ice at that location
originated as fi rn, and chemical and isotopic data indicate it grew in-situ with ground water
as the source (Moorman et al., 1996, p. 265; 1998, p. 761). Massive tabular ice bodies are
also known to occur on Ellesmere Island, where the ice is interbedded with fi ne-grained
marine sediments lying below the maximum limit of marine submergence (Pollard, 2000b).
The ice is interpreted as intra-sedimental in origin, the result of permafrost aggradation
into recently-emerged marine sediments.
ADVANCED READING
Astakhov, V. I., Kaplyanskaya, F. A., Tarnogradsky, V. D. (1996). Pleistocene permafrost of West
Siberia as a deformable glacier bed. Permafrost and Periglacial Processes , 7 , 165-191.
Mackay, J. R., Dallimore, S. R. (1992). Massive ice of the Tuktoyaktuk area, Western Arctic Coast,
Canada. Canadian Journal of Earth Sciences , 29 , 1235-1249.
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