608
Land-Ocean Systems in the Siberian Arctic: Dynamics and History
G. rubescens are evolutionary closely linked (Kennett and Srinivasan, 1983) and are
morphologically also quite similar. In Laptev Sea surface sediments only very few specimens
of G. bulloides and N. pachyderma have been reported so far (Tamanova, 1971). This
generally low number of specimens appears to be typical in this area and is corroborated by
more recent studies (Rossak, 1995; Bude, 1997).
Because a direct water mass influence from outside the Arctic Ocean seems unlikely to be
responsible for the occurrence of warm species in Holocene sediments, other processes such as
coastal erosion and reworking of older sediments may be considered. Although not mapped in
detail, cliffs composed of Miocene and Pliocene sediments are known to occur along the eastern
shores of the Laptev Sea (Okulitch et aI., 1989 Arctic Map) and are confirmed by recent field
observations (A. Basilyan, G. Ivanenko, P. Nikolskiy pers. com. 1997). Previous drilling in
the SE Laptev Sea yielded sediment successions down to the lower Miocene (Sudakov et aI.,
1991). But these sediments are shallow water sediments - like those from the terrestrial
outcrops - containing typically shallow-marine and freshwater microfossils. Furthermore,
detailed studies of the diatom and palynomorph assemblages in Laptev Sea surface sediments as
well as in core IK9373-10 could not confirm the possibility of reworking of older sediments
(Cremer, 1997; Kunz-Pirrung, this volume). However, previous studies have shown that
sediment transport by sea-ice is of major importance for sediment dynamics on Arctic shelfs
(Kempema et aI., 1989; Eicken et aI., 1997). Thus, sediment entrainment from shallow Arctic
shelfs and the later release of these sediments (Reimnitz et aI., 1987) may be a possible
mechanism to explain far-distance transport of recent or even much older fossil remains
(Abelmann, 1992; Reimnitz et aI., 1992). The mean field of sea-ice motion along the east
Siberian she1fs is from Bering Strait towards the Laptev Sea (Rigor, 1992). So, if the findings
of warm-water foraminifera in the Laptev Sea is due to sea-ice transport then the actual source
may be sought further east. But 'exotic' (mostly subtropical) planktic foraminifera have also
been reported from various Holocene and glacial deposits in the Barents and Kara seas area
(Gudina, 1966; Blaschishin et aI., 1985; Khusid et aI., 1995).
Conclusions
With the data presently available it is not possible to decipher the origin of the warm water
foraminiferal species in the Laptev Sea. It remains speCUlative if they had derived from
sediments deposited during times when subtropical water masses are known to have reached
the Arctic Ocean (Spiegler, 1996) or if they are of Holocene age. To eventually verify that the
findings of warm foraminiferal species in the Laptev Sea are actually caused by water inflow
during the Holocene further investigations are needed with regard to their true age. This
certainly should involve large quantities of sediment sampling in the hope that these large
samples may yield sufficient numbers of specimens for radiocarbon analyses.
Based on the foraminiferal record from the Lomonosov Ridge it is evident that the Arctic
Ocean fauna is composed of a single genus. Although this area is marked today by a perennial
coverage of sea-ice close to 100% with water temperatures in the upper 200 m well below 0 0 C
(Rudels, 1995), foraminiferal bioproductivity has increased steadily since about 7 ka. It is
therefore suggested that an inflow of non-polar water masses into the Arctic has a notable
influence on planktic productivity even at remote sites such as investigated in the central Arctic
Ocean. The relative changes of up to 5 % noted in the two coiling varieties of N. pachyderma
cannot be related to variations in surface water temperatures and, thus, seems independent of
major glacial-interglacial climate changes. The variability of the two coiling forms is more likely
caused by unknown population dynamics. To what extent the relatively small amount of Pacific
surface water inflow through Bering Strait (Coachman and Aagaard, 1988) is also influencing
Land-Ocean Systems in the Siberian Arctic: Dynamics and History
G. rubescens are evolutionary closely linked (Kennett and Srinivasan, 1983) and are
morphologically also quite similar. In Laptev Sea surface sediments only very few specimens
of G. bulloides and N. pachyderma have been reported so far (Tamanova, 1971). This
generally low number of specimens appears to be typical in this area and is corroborated by
more recent studies (Rossak, 1995; Bude, 1997).
Because a direct water mass influence from outside the Arctic Ocean seems unlikely to be
responsible for the occurrence of warm species in Holocene sediments, other processes such as
coastal erosion and reworking of older sediments may be considered. Although not mapped in
detail, cliffs composed of Miocene and Pliocene sediments are known to occur along the eastern
shores of the Laptev Sea (Okulitch et aI., 1989 Arctic Map) and are confirmed by recent field
observations (A. Basilyan, G. Ivanenko, P. Nikolskiy pers. com. 1997). Previous drilling in
the SE Laptev Sea yielded sediment successions down to the lower Miocene (Sudakov et aI.,
1991). But these sediments are shallow water sediments - like those from the terrestrial
outcrops - containing typically shallow-marine and freshwater microfossils. Furthermore,
detailed studies of the diatom and palynomorph assemblages in Laptev Sea surface sediments as
well as in core IK9373-10 could not confirm the possibility of reworking of older sediments
(Cremer, 1997; Kunz-Pirrung, this volume). However, previous studies have shown that
sediment transport by sea-ice is of major importance for sediment dynamics on Arctic shelfs
(Kempema et aI., 1989; Eicken et aI., 1997). Thus, sediment entrainment from shallow Arctic
shelfs and the later release of these sediments (Reimnitz et aI., 1987) may be a possible
mechanism to explain far-distance transport of recent or even much older fossil remains
(Abelmann, 1992; Reimnitz et aI., 1992). The mean field of sea-ice motion along the east
Siberian she1fs is from Bering Strait towards the Laptev Sea (Rigor, 1992). So, if the findings
of warm-water foraminifera in the Laptev Sea is due to sea-ice transport then the actual source
may be sought further east. But 'exotic' (mostly subtropical) planktic foraminifera have also
been reported from various Holocene and glacial deposits in the Barents and Kara seas area
(Gudina, 1966; Blaschishin et aI., 1985; Khusid et aI., 1995).
Conclusions
With the data presently available it is not possible to decipher the origin of the warm water
foraminiferal species in the Laptev Sea. It remains speCUlative if they had derived from
sediments deposited during times when subtropical water masses are known to have reached
the Arctic Ocean (Spiegler, 1996) or if they are of Holocene age. To eventually verify that the
findings of warm foraminiferal species in the Laptev Sea are actually caused by water inflow
during the Holocene further investigations are needed with regard to their true age. This
certainly should involve large quantities of sediment sampling in the hope that these large
samples may yield sufficient numbers of specimens for radiocarbon analyses.
Based on the foraminiferal record from the Lomonosov Ridge it is evident that the Arctic
Ocean fauna is composed of a single genus. Although this area is marked today by a perennial
coverage of sea-ice close to 100% with water temperatures in the upper 200 m well below 0 0 C
(Rudels, 1995), foraminiferal bioproductivity has increased steadily since about 7 ka. It is
therefore suggested that an inflow of non-polar water masses into the Arctic has a notable
influence on planktic productivity even at remote sites such as investigated in the central Arctic
Ocean. The relative changes of up to 5 % noted in the two coiling varieties of N. pachyderma
cannot be related to variations in surface water temperatures and, thus, seems independent of
major glacial-interglacial climate changes. The variability of the two coiling forms is more likely
caused by unknown population dynamics. To what extent the relatively small amount of Pacific
surface water inflow through Bering Strait (Coachman and Aagaard, 1988) is also influencing