274
Land-Ocean Systems in the Siberian Arctic: Dynamics and History
(Reimnitz et ai., 1992)_ This is the reason why sediment samples from first-year ice of the
Laptev Sea (Wollenburg, 1993) are probably not showing expected clear gradients, which were
found in mineralogical parameters in sediments from the shelf floor (clay: Wahsner 1995,
Wahsner et ai., 1996, 1998; heavy minerals: Lapina, 1965; Silverberg, 1972; Behrends et ai.
1996)_ Nevertheless, mineralogical data display an eastern-Laptev-Sea-influenced Transpolar
Drift and Polar branch in the central Arctic Ocean, while the Siberian branch can be related to
the western shelf area of the Laptev Sea_
Concerning the distribution of heavy minerals in the Arctic Ocean, a clear relation between the
mineralogical characteristics of the central Arctic Ocean and the heavy mineral inventory of the
Laptev Sea shelf and slope is obvious. Underneath the Siberian branch, a clinopyroxene
maximum can be related to the western Laptev Sea. The sea-ice-sediment input from the Kara
Sea is probably rather small due to deeper water depth and therefore worse conditions for
sediment entrainment into sea ice (Kempema et aI., 1989; Ntirnberg et aI., 1995; Pfirmann et
aI., 1989, 1997). Based on the low orthopyroxene concentrations the Kara Sea can be excluded
as a main source. The generally low orthopyroxene concentration and, compared with the
Laptev Sea, lower contents of clinopyroxene also suggest the East Siberian Sea not to be a
potential source area.
Underneath the Transpolar Drift as well as the Polar Branch the mineralogical characteristics
show a heavy mineral pattern related to the eastern Laptev Sea shelf and slope. The values of
heavy mineral components are highly variable on the Lomonosov Ridge, probably due to
mixing and export of sediment-laden sea ice of the Beaufort Gyre into the Transpolar Drift
System. This is indicated by a higher content of detrital carbonate, which does not occur in
such high amounts on the Siberian shelves. Until now, detrital carbonate is not found in the
sea-ice sediment samples. On the East Siberian Sea shelf detrital carbonate is not listed as a
separate component (Figure 7), but included in "traces", showing an irregular distribution with
only two samples with high values of 4 % (Naugler, 1967).
Detrital carbonate is not only indicating the influence of the Beaufort Gyre and therefore the
sediment input from the Amerasian shelves into the eastern Arctic Ocean (Darby et aI., 1989;
N0rgaard-Pedersen, 1996), but also shows the input from Svalbard along the Barents Sea
continental slope (Solheim and Elverh0i, 1996; Vogt 1997). In this area, however, the
interpretation is more difficult due to mixing of signals, caused by different transport
mechanisms of sediment, such as ice rafting and melting, and downslope transport of sediment.
Another mineral group typical for the Amerasian shelves are opaque minerals. Other mineral
combinations already excluded the Kara Sea (see above), where also higher amounts of
opaques were found, as a main source. Thus, the ice-rafted sediment from the Beaufort Sea and
the Chukchi Sea transported via the Beaufort Gyre to the Lomonosov Ridge, are probably
causing the slightly higher concentration of opaque minerals in the Arctic Ocean sediment in
comparison to the Laptev Sea shelf sediments. The discrepancy of concentrations of
investigated heavy minerals found on the shelf in comparison with those in the river sediments
are probably due to different maximum output of suspended particular matter of the single
rivers and/or the different hydromorphology.
Conclusion
Heavy minerals in the Arctic Ocean were studied with respect to their relevance for tracing
transport pathways. This study shows that heavy minerals can be used to identify source areas
and to reconstruct sea-ice sediment input and surface water circulation patterns. The
investigation of heavy minerals on core material will give new important information about past
sea-ice drift pattern.
Land-Ocean Systems in the Siberian Arctic: Dynamics and History
(Reimnitz et ai., 1992)_ This is the reason why sediment samples from first-year ice of the
Laptev Sea (Wollenburg, 1993) are probably not showing expected clear gradients, which were
found in mineralogical parameters in sediments from the shelf floor (clay: Wahsner 1995,
Wahsner et ai., 1996, 1998; heavy minerals: Lapina, 1965; Silverberg, 1972; Behrends et ai.
1996)_ Nevertheless, mineralogical data display an eastern-Laptev-Sea-influenced Transpolar
Drift and Polar branch in the central Arctic Ocean, while the Siberian branch can be related to
the western shelf area of the Laptev Sea_
Concerning the distribution of heavy minerals in the Arctic Ocean, a clear relation between the
mineralogical characteristics of the central Arctic Ocean and the heavy mineral inventory of the
Laptev Sea shelf and slope is obvious. Underneath the Siberian branch, a clinopyroxene
maximum can be related to the western Laptev Sea. The sea-ice-sediment input from the Kara
Sea is probably rather small due to deeper water depth and therefore worse conditions for
sediment entrainment into sea ice (Kempema et aI., 1989; Ntirnberg et aI., 1995; Pfirmann et
aI., 1989, 1997). Based on the low orthopyroxene concentrations the Kara Sea can be excluded
as a main source. The generally low orthopyroxene concentration and, compared with the
Laptev Sea, lower contents of clinopyroxene also suggest the East Siberian Sea not to be a
potential source area.
Underneath the Transpolar Drift as well as the Polar Branch the mineralogical characteristics
show a heavy mineral pattern related to the eastern Laptev Sea shelf and slope. The values of
heavy mineral components are highly variable on the Lomonosov Ridge, probably due to
mixing and export of sediment-laden sea ice of the Beaufort Gyre into the Transpolar Drift
System. This is indicated by a higher content of detrital carbonate, which does not occur in
such high amounts on the Siberian shelves. Until now, detrital carbonate is not found in the
sea-ice sediment samples. On the East Siberian Sea shelf detrital carbonate is not listed as a
separate component (Figure 7), but included in "traces", showing an irregular distribution with
only two samples with high values of 4 % (Naugler, 1967).
Detrital carbonate is not only indicating the influence of the Beaufort Gyre and therefore the
sediment input from the Amerasian shelves into the eastern Arctic Ocean (Darby et aI., 1989;
N0rgaard-Pedersen, 1996), but also shows the input from Svalbard along the Barents Sea
continental slope (Solheim and Elverh0i, 1996; Vogt 1997). In this area, however, the
interpretation is more difficult due to mixing of signals, caused by different transport
mechanisms of sediment, such as ice rafting and melting, and downslope transport of sediment.
Another mineral group typical for the Amerasian shelves are opaque minerals. Other mineral
combinations already excluded the Kara Sea (see above), where also higher amounts of
opaques were found, as a main source. Thus, the ice-rafted sediment from the Beaufort Sea and
the Chukchi Sea transported via the Beaufort Gyre to the Lomonosov Ridge, are probably
causing the slightly higher concentration of opaque minerals in the Arctic Ocean sediment in
comparison to the Laptev Sea shelf sediments. The discrepancy of concentrations of
investigated heavy minerals found on the shelf in comparison with those in the river sediments
are probably due to different maximum output of suspended particular matter of the single
rivers and/or the different hydromorphology.
Conclusion
Heavy minerals in the Arctic Ocean were studied with respect to their relevance for tracing
transport pathways. This study shows that heavy minerals can be used to identify source areas
and to reconstruct sea-ice sediment input and surface water circulation patterns. The
investigation of heavy minerals on core material will give new important information about past
sea-ice drift pattern.