418
Land-Ocean Systems in the Siberian Arctic: Dynamics and History
and about SoC for June on the northern Taymyr Peninsula, insufficient for the establishment of
a boreal forest.
The transition from the Boreal to the Atlantic period, as recorded in the cores from LevinsonLessing and Lama Lakes (LL8 and L8), is characterized by significant decreases in AP values,
indicating a slight climatic deterioration. This event presumably coincides with the
"Novosanchu-govskyi Cooling" in Central Siberia, which is dated to 8.0 - 7.9 ka BP
(Khotinskiy, 1984) and probably also occurred in West Siberia, North America, and Europe
(Kind, 1974).
Within the Atlantic period, different vegetation trends are recorded on the northern and
southern Taymyr Peninsula. In the Levinson-Lessing Lake profile, slowly but continuously
decreasing AP values (shrubs) indicate that the climatic deterioration continued throughout the
Atlantic period. As a consequence, the Boreal shrub tundra was gradually eliminated and
replaced by a graminoid-herb tundra. Simultaneously rising Cyperaceae values may indicate
increasing moisture during this period, whilst rising Pinus contents are traced back to
increasing long-distance transport from beyond the studied area.
At Lama Lake, in contrast, the Atlantic period was characterized by rather small vegetation
changes. The climate was favourable for a continuous advance of spruce (Picea obovata) and
for the establishment of a closed taiga composed of Larix, Betula, and Picea. Hence, the
decrease in summer temperatures of about I to 2°C, indicated by the elimination of shrub tundra
at Levinson-Lessing Lake, was either lower in the Lama Lake area or too slight to diminish the
larch-spruce-birch forests persistently. In the upper part of the Atlantic period, small variations
in the Picea concentration at Lama Lake may coincide with Alnus and Betula variations in the
Levinson-Lessing Lake profile.
The Atlantic/Subboreal boundary in the diagram from Levinson-Lessing Lake (LL8ILL9) is
poorly recorded by the pollen assemblage. It is probably located at 350 em, where a linear
interpolation using mean Holocene sedimentation rates indicates an age of 5.0 ka BP and where
NAP values exceed 50 %. The PAZ LL 9 comprises the Subboreal and Subatlantic periods,
which cannot be separated from pollen stratigraphic aspects because arboreal indicators are
missing. At a depth of about 220 em (around 3.0 ka BP), a more or less continuous increase of
non-arboreal pollen changes to roughly constant NAP values. This is the time when the climatic
decline, which had started in the Atlantic period, probably reached its end. The elimination of
the birch and alder shrubs was complete, resulting in a nearly pure grass-herb tundra until the
present.
In the Lama Lake diagram, in contrast, the Subboreal period (L9; 5.0 - 2.5 ka BP) is clearly
expressed. From alternating spruce values it can be subdivided into two cooling events (PAZs
L9a and L9c) and one intervening warming event (PAZ L9b), which have been described
previously by Khotinskiy (1984). The slight Subboreal temperature variations are best reflected
by the spruce values, because the Lama Lake area was probably very close to the northern
range of Picea obovata during that period. Following the last Subboreal cooling event, spruce
values remain below 5 % during Subboreal times (LlO; 2.5 - 0 ka BP), whereas NAP values
increase distinctly. A spread of heliophytes, such as Artemisia, Thalictrum, Filicinae,
Lycopodium, and Selaginella suggest a thinning of the previous dense forest communities, and
high values of Sphagnum may indicate increased precipitation.
Shift of vegetation zones in northern Central Siberia
The detailed palynological investigations on the sediment cores PG 1111 and PG 1228,
presented and discussed above, have illustrated that the Weichselian and Holocene evolution of
the summer temperatures on the Taymyr Peninsula is best reflected in the contents of arboreal
Land-Ocean Systems in the Siberian Arctic: Dynamics and History
and about SoC for June on the northern Taymyr Peninsula, insufficient for the establishment of
a boreal forest.
The transition from the Boreal to the Atlantic period, as recorded in the cores from LevinsonLessing and Lama Lakes (LL8 and L8), is characterized by significant decreases in AP values,
indicating a slight climatic deterioration. This event presumably coincides with the
"Novosanchu-govskyi Cooling" in Central Siberia, which is dated to 8.0 - 7.9 ka BP
(Khotinskiy, 1984) and probably also occurred in West Siberia, North America, and Europe
(Kind, 1974).
Within the Atlantic period, different vegetation trends are recorded on the northern and
southern Taymyr Peninsula. In the Levinson-Lessing Lake profile, slowly but continuously
decreasing AP values (shrubs) indicate that the climatic deterioration continued throughout the
Atlantic period. As a consequence, the Boreal shrub tundra was gradually eliminated and
replaced by a graminoid-herb tundra. Simultaneously rising Cyperaceae values may indicate
increasing moisture during this period, whilst rising Pinus contents are traced back to
increasing long-distance transport from beyond the studied area.
At Lama Lake, in contrast, the Atlantic period was characterized by rather small vegetation
changes. The climate was favourable for a continuous advance of spruce (Picea obovata) and
for the establishment of a closed taiga composed of Larix, Betula, and Picea. Hence, the
decrease in summer temperatures of about I to 2°C, indicated by the elimination of shrub tundra
at Levinson-Lessing Lake, was either lower in the Lama Lake area or too slight to diminish the
larch-spruce-birch forests persistently. In the upper part of the Atlantic period, small variations
in the Picea concentration at Lama Lake may coincide with Alnus and Betula variations in the
Levinson-Lessing Lake profile.
The Atlantic/Subboreal boundary in the diagram from Levinson-Lessing Lake (LL8ILL9) is
poorly recorded by the pollen assemblage. It is probably located at 350 em, where a linear
interpolation using mean Holocene sedimentation rates indicates an age of 5.0 ka BP and where
NAP values exceed 50 %. The PAZ LL 9 comprises the Subboreal and Subatlantic periods,
which cannot be separated from pollen stratigraphic aspects because arboreal indicators are
missing. At a depth of about 220 em (around 3.0 ka BP), a more or less continuous increase of
non-arboreal pollen changes to roughly constant NAP values. This is the time when the climatic
decline, which had started in the Atlantic period, probably reached its end. The elimination of
the birch and alder shrubs was complete, resulting in a nearly pure grass-herb tundra until the
present.
In the Lama Lake diagram, in contrast, the Subboreal period (L9; 5.0 - 2.5 ka BP) is clearly
expressed. From alternating spruce values it can be subdivided into two cooling events (PAZs
L9a and L9c) and one intervening warming event (PAZ L9b), which have been described
previously by Khotinskiy (1984). The slight Subboreal temperature variations are best reflected
by the spruce values, because the Lama Lake area was probably very close to the northern
range of Picea obovata during that period. Following the last Subboreal cooling event, spruce
values remain below 5 % during Subboreal times (LlO; 2.5 - 0 ka BP), whereas NAP values
increase distinctly. A spread of heliophytes, such as Artemisia, Thalictrum, Filicinae,
Lycopodium, and Selaginella suggest a thinning of the previous dense forest communities, and
high values of Sphagnum may indicate increased precipitation.
Shift of vegetation zones in northern Central Siberia
The detailed palynological investigations on the sediment cores PG 1111 and PG 1228,
presented and discussed above, have illustrated that the Weichselian and Holocene evolution of
the summer temperatures on the Taymyr Peninsula is best reflected in the contents of arboreal