410
Land-Ocean Systems in the Siberian Arctic: Dynamics and History
are around 250 AP, and for parts of extremely cold sequences they decrease down to 20 - 30
AP.
The palynological results are represented as total pollen diagrams (Figures 2 and 3), i.e. the
pollen sums (100 %) include all pollen, with the exception of aquatics, spores, and algae
(Pediastrum).
In the diagram from Lama Lake (Figure 2), the Alnus curve consists of tree alders (Alnus) and
of shrub alders, which in the Russian literature are generally called" Alnaster". Its pollen grains
are very similar to those of Alnus viridis (small and oval pores) and are therefore listed in the
diagram under ,,Alnus viridis-type". The Betula curve consists of tree birches (Betula trees),
Betula nana (smaller pollen grains) and other shrub birches without clearly visible vestibulum
(several species, which are collected under "Betula exilis-type"). Not mentioned are very rare
finds of Hippophae, Ephedra distachya-type and Ericaceae (Ledum and Vaccinium-type). An
initial, regional interpretation of the palynological results from the Lama Lake core PG 1111 was
presented by Hahne and Melles (1997).
In the diagram from Levinson-Lessing Lake (Figure 3), the presence of Larix, Picea, and
Pinus pollens is probably the result of long-distance transport. The curves of Alnus and Betula
consist predominantly of shrub types as tree pollen contribute less than 5 %. Hippophae,
Ephedra distachya-type, Primulaceae, Lentibulariaceae, Liliaceae, Dipsacaceae, Polygonaceae,
Epilobium, Boraginaceae, Scrophulariaceae, Centaurea-types, Pedicularis and Lloydia are not
recorded due to their extremely rare occurrence.
Results aud stratigraphy
The 10.6 m long sediment core PG 1111 from the central part of Lama Lake did not reach the
lacustrine sediment base. It consists of clayey silts and silty clays, with sand contents of less
than 5 % (Figure 2). Clastic sediment components clearly predominate over biogenic
components. Neither terrestrial macrofossils, which are promising for reliable radiocarbon
dating, nor time-synchronous marker horizons, such as tephra layers, were found. The
sediment color change repeatedly throughout the succession. Within the uppermost 0.3 m and
below 7.3 m, brownish and yellowish colors indicate oxic conditions, whereas in the
intervening horizon, grayish and dark greenish colors indicate anoxic conditions in the
sediment. Down to a depth of 7.2 m the sediment is well to crudely stratified, below 7.2 m it is
laminated with individual layers being less than 1 mm thick.
The pollen diagram from core PG 1111 was subdivided into eleven regional pollen
assemblage zones (PAZs), LI - LIl (Table 2, Figure 2), whose boundaries reflect distinct
vegetation changes in the catchment area of Lama Lake. In order to obtain initial chronological
information for this core, the PAZ succession was correlated with the Late Weichselian and
Holocene chronozones defined by Mangerud et al. (1974). This correlation can only supply a
rough approximation of sediment ages because: 1) the climate and vegetation changes in Siberia
could have been time-transgressive relative to those in northern Europe, which have been
studied and dated by Mangerud et al. (1974), 2) the ages of the zone boundaries, originally
defined by radiocarbon dates measured on bulk sediment, underwent repeated modifications
with progress in radiocarbon dating techniques (Wohlfarth, 1996), and 3) some of the zone
boundaries, such as the Younger Dryas to Preboreal boundaries, are dated to 14C age plateaus,
hampering calibrations and thus accurate age determinations (Bjorck et a!., 1996).
Nevertheless. the correlation of the PAZs with the chronozones supplies sufficient information
for a discussion of general trends in the climate and vegetation history in the Siberian study
area.
Land-Ocean Systems in the Siberian Arctic: Dynamics and History
are around 250 AP, and for parts of extremely cold sequences they decrease down to 20 - 30
AP.
The palynological results are represented as total pollen diagrams (Figures 2 and 3), i.e. the
pollen sums (100 %) include all pollen, with the exception of aquatics, spores, and algae
(Pediastrum).
In the diagram from Lama Lake (Figure 2), the Alnus curve consists of tree alders (Alnus) and
of shrub alders, which in the Russian literature are generally called" Alnaster". Its pollen grains
are very similar to those of Alnus viridis (small and oval pores) and are therefore listed in the
diagram under ,,Alnus viridis-type". The Betula curve consists of tree birches (Betula trees),
Betula nana (smaller pollen grains) and other shrub birches without clearly visible vestibulum
(several species, which are collected under "Betula exilis-type"). Not mentioned are very rare
finds of Hippophae, Ephedra distachya-type and Ericaceae (Ledum and Vaccinium-type). An
initial, regional interpretation of the palynological results from the Lama Lake core PG 1111 was
presented by Hahne and Melles (1997).
In the diagram from Levinson-Lessing Lake (Figure 3), the presence of Larix, Picea, and
Pinus pollens is probably the result of long-distance transport. The curves of Alnus and Betula
consist predominantly of shrub types as tree pollen contribute less than 5 %. Hippophae,
Ephedra distachya-type, Primulaceae, Lentibulariaceae, Liliaceae, Dipsacaceae, Polygonaceae,
Epilobium, Boraginaceae, Scrophulariaceae, Centaurea-types, Pedicularis and Lloydia are not
recorded due to their extremely rare occurrence.
Results aud stratigraphy
The 10.6 m long sediment core PG 1111 from the central part of Lama Lake did not reach the
lacustrine sediment base. It consists of clayey silts and silty clays, with sand contents of less
than 5 % (Figure 2). Clastic sediment components clearly predominate over biogenic
components. Neither terrestrial macrofossils, which are promising for reliable radiocarbon
dating, nor time-synchronous marker horizons, such as tephra layers, were found. The
sediment color change repeatedly throughout the succession. Within the uppermost 0.3 m and
below 7.3 m, brownish and yellowish colors indicate oxic conditions, whereas in the
intervening horizon, grayish and dark greenish colors indicate anoxic conditions in the
sediment. Down to a depth of 7.2 m the sediment is well to crudely stratified, below 7.2 m it is
laminated with individual layers being less than 1 mm thick.
The pollen diagram from core PG 1111 was subdivided into eleven regional pollen
assemblage zones (PAZs), LI - LIl (Table 2, Figure 2), whose boundaries reflect distinct
vegetation changes in the catchment area of Lama Lake. In order to obtain initial chronological
information for this core, the PAZ succession was correlated with the Late Weichselian and
Holocene chronozones defined by Mangerud et al. (1974). This correlation can only supply a
rough approximation of sediment ages because: 1) the climate and vegetation changes in Siberia
could have been time-transgressive relative to those in northern Europe, which have been
studied and dated by Mangerud et al. (1974), 2) the ages of the zone boundaries, originally
defined by radiocarbon dates measured on bulk sediment, underwent repeated modifications
with progress in radiocarbon dating techniques (Wohlfarth, 1996), and 3) some of the zone
boundaries, such as the Younger Dryas to Preboreal boundaries, are dated to 14C age plateaus,
hampering calibrations and thus accurate age determinations (Bjorck et a!., 1996).
Nevertheless. the correlation of the PAZs with the chronozones supplies sufficient information
for a discussion of general trends in the climate and vegetation history in the Siberian study
area.