Geology and Paleoceanography
terial from the interior areas, inland from the Arctic
Ocean, such as the Precambrian Shield. Grain-type
percentages in glacial deposits on and around these
islands closely match rock types of local formations.
Heavy mineral and iron oxide grains show less-clear
affinities to local rock types but generally corrobo-
rate the local nature of tills and glaciomarine sedi-
ments in the Queen Elizabeth Islands.
Thick
Ice
Today's Beaufort Gyre circulation in the western
Arctic Ocean, a clockwise ice drift, cannot explain
the observed compositional differences between wide-
ly spaced core locations. The data obtained thus far
suggest that the surface circulation in the western
Arctic was toward Fram Strait, even along the Cana-
dian Arctic coast during glacial intervals. This means
that surface currents were opposite or perpendicular
to the southwestward currents today within a couple
of hundred kilometers of the Canadian Arctic coast. Thus large numbers of
Iceberg drift tracks
and surface currents
icebergs moved northeastward near the coast and into the North Atlantic dur-
for earlier glacial
ing glacial maxima, while a thick floating ice cap blocked or greatly inhibited
maxima in the west-
ern Arctic Ocean
icebergs from reaching the central and western parts of the Arctic Ocean. This
based on drop-
is further supported by the slower sedimentation rates in these central areas.
stones and iron
Unusual magnetite spherules (4060 m) with about 618% zinc oxide
oxide grains. The
zone of thick ice
and 18% nickel oxide were found at over 30 sites in the Queen Elizabeth
inhibits iceberg drift
Islands and in several Arctic Ocean cores in sediment as old as 780,000 years.
and causes low
sedimentation rates.
Iron meteorites lack zinc because of its volatility at temperatures of atmo-
Arrows depict ice-
spheric entry, so an impact event in zinc-bearing limestones such as the Haugh-
berg drift from the
ton Astrobleme (~22 million years ago) is still considered to be a likely expla-
Laurentide Ice Sheet
(open arrows) and
nation for such spherules. However, a detailed search for these spherules in
glaciers from the
ejecta from the Haughton Astrobleme on Devon Island was negative. Thus, if
Queen Elizabeth
Islands (solid
these spherules were formed by such an event, it is yet to be discovered in the
arrows). Core loca-
Queen Elizabeth Islands.
tions used for this
reconstruction are
shown as black dots.
REFERENCE
Darby, D.A. and J.F. Bischof (1996) A statistical approach to source determi-
nation of lithic and Fe oxide grains: An example from the Alpha Ridge, Arctic
Ocean. Journal of Sedimentary Research, 66: 599607.
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