1994 Arctic Ocean Section
1
2
Ellesmere Is.
GREENLAND
Northern
Axel Heiberg Is.
3
Axel Heiberg-
4
Ellef Ringnes Is.
Source areas for
10
North
Arctic ice-rafted
Melville and
Devon Is.
Slope
Bathurst Is.
6
debris based on
statistically unique
5
ALASKA
7
8
grain-type content
Grinnell Peninsula
N
and chemistry of
70
Lancaster Sound
iron oxide grains.
Not shown is
9
Banks and
another area in the
Victoria Is.
Mackenzie Delta
Kara Sea and the
and Tributaries
102 till and glacio-
N
65
marine sediment
sample locations
CANADA
used to define
these areas.
tributes on average less than 10% to the ice-rafted detritus in the cores anal-
yzed. Areas of existing ice caps such as Ellesmere Island, Axel Heiberg Island
and Greenland contribute even less to the western Arctic Ocean. About 25%
of the iron oxide grains in the studied Arctic Ocean core samples were from
unknown source areas. All glacial sources except those of the Barents Shelf and
adjacent land masses were sampled to varying degrees of thoroughness. We
suspect that many of the iron oxide grains from presently unknown sources
(the average from 17 cores is 26%) may have been rafted by sea ice from the
Russian shelves. This has serious implications because of the modern pollution
from radioactive dumps and other pollutants attached to sediment in parts of this
shelf area.
Down-core changes in source area contributions show that cyclic surging of
ice sheets and ice caps has occurred at least throughout the last 780,000 years
in the Arctic. The cyclicity is less than about 30,000 years and probably less than
10,000 years during glacial intervals, but because of the lack of a more detailed
chronostratigraphy in the Arctic cores, the frequency cannot be resolved further.
Pulses of ice rafting from different sources in 14C-dated Holocene sediments
(<10,000 years old) of the central Arctic Ocean lasted less than 2,000 years.
The Laurentide ice sheet that calved into the Arctic Ocean from Melville or
Banks Island to the Mackenzie Delta area coexisted with several small ice caps or
possibly a larger ice sheet over the Queen Elizabeth Islands. This is based on the
discovery of detritus from both ice masses in the same 0.5- to 1-cm-thick core
samples.
The last glaciation in the Queen Elizabeth Islands transported little ma-
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