638
Land-Ocean Systems in the Siberian Arctic: Dynamics and History
Material and stratigraphy
During RV Polarstern Cruise ARK-IX/4 sediment cores were recovered on four transects from
the Laptev Sea continental margin (Fiitterer, 1994; Niirnberg et a!., 1995). The three cores
PS2471, PS2474, and PS2476 discussed in this paper, were obtained from the western
continental slope at water depths of 3047 m, 1494 m, and 524 m, respectively (Figures 2 and 3;
cf. Table 2). In all cores, the sediments mainly consist of brown (upper part of the sedimentary
sequences), olive, gray to dark gray sandy, silty clays with abundant black spots. Occasionally,
sandy turbidites are intercalated in cores PS2471 and PS2474. Based on the visual core
description (Fiitterer, 1994), the sediments contain relatively high amounts of terrigenous
organic matter (plant fibers). Despite the turbidites, the sediments do not show any major
lithological change, thus preventing visual core correlation. Magnetic susceptibility records,
however, provide an excellent tool for core correlation (Figure 4; Fiitterer, 1994; Niirnberg et
a!., 1995), which is the basis for the correlation shown in Figures 5 and 6.
Based on the abundance maximum of the coccolithophoride Gephyrocapsa spp. which is an
indicator for Arctic interglacials (Gard, 1988), the upper 50 cm of Core PS2471 (Figure 5, Unit
A) is assumed to be of Oxygen Isotope Stage 1 (Holocene and late Termination 1) age
(Niirnberg et aI., 1995). This is also suported by correlation of magnetic susceptibility records
of cores PS 2471, PS2474, and PS2476 with the AMS 14C-dated magnetic susceptibility
record of the nearby Core PS2778 (Figures 3 and 4). This would result in Oxygen Isotope
Stage 1 (0-12 ka) mean linear sedimentation rates (LSR) of approximately 4 cm/ky, 22 cm/ky,
and 50 cm/ky in cores PS2471, PS2474, and PS2476, respectively. The occurrence of
Gephyrocapsa spp. between 200 and 300 cm in the sedimentary sequence of Core PS2471 is
related by Niirnberg et a!. (1995) to the Last Interglacial (Oxygen Isotope Stage 5). In
sedimentary records from the Nansen Basin, however, Gephyrocapsa spp. was also recorded
in Oxygen Isotope Stage 3 (Baumann, 1990).
Based on a detailed sedimentological study performed in the western Laptev Sea continental
margin area, including P ARASOUND profiles, magnetic susceptibility and clay mineral records
as well as AMS 14C datings, intervals with major occurrences of turbidites and debris flows are
correlated with glacial stages of lowered sea level (Weiel, 1997). This may suggest that incores
PS2471 and PS2474 the (upper) turbidite may fall either into Oxygen Isotope Stage 4 or
Oxygen Isotope Stage 2. Especially during Oxygen Isotope Stage 4, a deposition of thick
sequences of debris flows in the western Laptev Sea, triggered by a (in comparison to the Last
Glacial Maximum much more extended) major ice sheet on Taymyr Peninsula and thus
drastically increased supply of terrigenous matter, has been postulated by Weiel (1997) and
Niessen et al. (1997). If the depositional area of cores PS2471 and PS2474 is connected to this
sedimentary regime, the turbidites in Unit C are probably of Oxygen Isotope Stage 4 age or
older. If, on the other hand, the two cores are more influenced by processes controlling the
eastern Laptev Sea (i.e., influence by river Lena), a younger age of the upper turbidites is
possible. Taking the mean Holocene sedimentation rates and assuming that drastically reduced
pre-Holocene sedimentation rates are rather unrealistic (which is supported by the high preHolocene sedimentation rates recorded in several other cores from the central and eastern
Laptev-Sea area; Bauch et aI., 1996; Spielhagen et aI., 1996; Fahl and Stein, 1997b), an
Oxygen Isotope Stage 2 (LGM) age seems to be more probable for the upper turbidites. That
means, Unit B (Figure 5) may represent post-LGMlTermination I, overlying the turbidites of
Unit C. The two lower turbidites in Unit C of Core PS2471, occurring below the interval
characterized by significant abundances of (Oxygen Isotope Stage 3 ?) Gephyrocapsa spp.,
may have been deposited during older (Oxygen Isotope Stage 4?) glacial periods.
Based on the present data base, the stratigraphic framework of the three cores is still
preliminary; it is not possible yet to prefer one age model and reject the other. The stratigraphy
Land-Ocean Systems in the Siberian Arctic: Dynamics and History
Material and stratigraphy
During RV Polarstern Cruise ARK-IX/4 sediment cores were recovered on four transects from
the Laptev Sea continental margin (Fiitterer, 1994; Niirnberg et a!., 1995). The three cores
PS2471, PS2474, and PS2476 discussed in this paper, were obtained from the western
continental slope at water depths of 3047 m, 1494 m, and 524 m, respectively (Figures 2 and 3;
cf. Table 2). In all cores, the sediments mainly consist of brown (upper part of the sedimentary
sequences), olive, gray to dark gray sandy, silty clays with abundant black spots. Occasionally,
sandy turbidites are intercalated in cores PS2471 and PS2474. Based on the visual core
description (Fiitterer, 1994), the sediments contain relatively high amounts of terrigenous
organic matter (plant fibers). Despite the turbidites, the sediments do not show any major
lithological change, thus preventing visual core correlation. Magnetic susceptibility records,
however, provide an excellent tool for core correlation (Figure 4; Fiitterer, 1994; Niirnberg et
a!., 1995), which is the basis for the correlation shown in Figures 5 and 6.
Based on the abundance maximum of the coccolithophoride Gephyrocapsa spp. which is an
indicator for Arctic interglacials (Gard, 1988), the upper 50 cm of Core PS2471 (Figure 5, Unit
A) is assumed to be of Oxygen Isotope Stage 1 (Holocene and late Termination 1) age
(Niirnberg et aI., 1995). This is also suported by correlation of magnetic susceptibility records
of cores PS 2471, PS2474, and PS2476 with the AMS 14C-dated magnetic susceptibility
record of the nearby Core PS2778 (Figures 3 and 4). This would result in Oxygen Isotope
Stage 1 (0-12 ka) mean linear sedimentation rates (LSR) of approximately 4 cm/ky, 22 cm/ky,
and 50 cm/ky in cores PS2471, PS2474, and PS2476, respectively. The occurrence of
Gephyrocapsa spp. between 200 and 300 cm in the sedimentary sequence of Core PS2471 is
related by Niirnberg et a!. (1995) to the Last Interglacial (Oxygen Isotope Stage 5). In
sedimentary records from the Nansen Basin, however, Gephyrocapsa spp. was also recorded
in Oxygen Isotope Stage 3 (Baumann, 1990).
Based on a detailed sedimentological study performed in the western Laptev Sea continental
margin area, including P ARASOUND profiles, magnetic susceptibility and clay mineral records
as well as AMS 14C datings, intervals with major occurrences of turbidites and debris flows are
correlated with glacial stages of lowered sea level (Weiel, 1997). This may suggest that incores
PS2471 and PS2474 the (upper) turbidite may fall either into Oxygen Isotope Stage 4 or
Oxygen Isotope Stage 2. Especially during Oxygen Isotope Stage 4, a deposition of thick
sequences of debris flows in the western Laptev Sea, triggered by a (in comparison to the Last
Glacial Maximum much more extended) major ice sheet on Taymyr Peninsula and thus
drastically increased supply of terrigenous matter, has been postulated by Weiel (1997) and
Niessen et al. (1997). If the depositional area of cores PS2471 and PS2474 is connected to this
sedimentary regime, the turbidites in Unit C are probably of Oxygen Isotope Stage 4 age or
older. If, on the other hand, the two cores are more influenced by processes controlling the
eastern Laptev Sea (i.e., influence by river Lena), a younger age of the upper turbidites is
possible. Taking the mean Holocene sedimentation rates and assuming that drastically reduced
pre-Holocene sedimentation rates are rather unrealistic (which is supported by the high preHolocene sedimentation rates recorded in several other cores from the central and eastern
Laptev-Sea area; Bauch et aI., 1996; Spielhagen et aI., 1996; Fahl and Stein, 1997b), an
Oxygen Isotope Stage 2 (LGM) age seems to be more probable for the upper turbidites. That
means, Unit B (Figure 5) may represent post-LGMlTermination I, overlying the turbidites of
Unit C. The two lower turbidites in Unit C of Core PS2471, occurring below the interval
characterized by significant abundances of (Oxygen Isotope Stage 3 ?) Gephyrocapsa spp.,
may have been deposited during older (Oxygen Isotope Stage 4?) glacial periods.
Based on the present data base, the stratigraphic framework of the three cores is still
preliminary; it is not possible yet to prefer one age model and reject the other. The stratigraphy