488
Land-Ocean Systems in the Siberian Arctic: Dynamics and History
Pollen assemblages obtained from profile LA022 (Figure 7) indicated warmer climatic
conditions for the accumulation period of this section than we have at present A rich shrubtundra vegetation with open larch and birch woods dominated_ During the formation of zone I
and 3, a more humid climatic character can be assumed_ The pollen assemblages of zone 2
suggested drier conditions_ There was a significant increase of shrub pollen percentage with
dwarf birch dominance_ Tree pollen, including both alder types as well as spores, decreased_ A
small increase of Poaceae and other herbs was observed in the NAP_ The typical xerophyte
pollen of Ephedra was also observed_ The high amounts of redeposited Mesozoic but
apparently Cretaceous pollen in all samples is significant They indicate that glaciogenic
deposits of unit I were strongly eroded and redistributed_ Because all radiocarbon data
indicated ages greater than 46000 yr BP, we suppose that these sediments were likely formed
not later than the first warming phase of the Kargin Interstadial. Without a doubt, active glacier
ice decay took place during this time, leading to a strong activation of erosional processes and
to a rise of accumulation in adjacent lakes_
Site LA025 represents fluvio-Iacustrine (and likely deltaic) sediments which were exposed at
the basis of the 55 - 60 m lake terrace to the east of the Tolton-Pastakh-Yuryakh River mouth
(Figures I and 2)_ Exposed sediments showed a clear bedding with an inclination of about 10°
towards the W -WNW. The lower part of the section consisted of light grey sand interlaminated
by silt and clay with characteristic rust-coloured layer boundaries. Among various
allochthonous plant remains, tree branches were present From 3.6 to 2.8 m depth, layered
sands containing coal detritus and small gravels were interbedded by numerous floating peat
layers. The overlying horizon consisted of sand, silt and clay interbedding with several tree and
shrub remains as well as crushed angular gravels and pebbles. Sub vertical grass roots were
found in the upper two meters. The latter sediments seemed to be influenced by recent or
Holocene slope and soil forming processes. For wood remains from this section, radiocarbon
ages between about 34000 yr and more than 40000 yr BP were recorded including some
inverse data. A dating of 285OO±400 yr BP was obtained from floating peat material at a depth
of 2.8 m. These results indicate that the sediments contained potentially redeposited plant
material, especially wood remains.
The pollen diagram of site LA025 (Figure 8) showed similarities to that of site LA022
(Figure 7). Small percentages of NAP and a dominance of Betula sect. Nanea and Alnaster are
characteristic features. However, in contrast to site LA022, the pollen percentage of trees,
especially of Betula Alba and Alnus, was slightly higher at site LA025. Similarities between
both sites also existed in the composition of NAP and spores. Poaceae and Ericaceae were
found in appreciable amounts, with less Artemisia and Cyperaceae. For other herbs, Asteraceae
and Cichoriaceae were continuously present, and Carophyllaceae, Pedicularis, Dryas and
others less frequently. Spores observed belonged to Bryales, Polypodiaceae and Lycopodium
(especially L. alpinum, less L. pungens, and least of all L. annotium , L. complanatum and L.
appressum). The spore pollen assemblages of zones I and 3 in the diagram correspond to a
shrub tundra vegetation growing under humid and warmer climatic conditions than those of
today. The pollen assemblages of zone 2 indicate the development of an almost pure birchshrub tundra, sparsely distributed, with open larch forest under drier but still warmer climatic
conditions than today. The considerable amounts of redeposited Cretaceous pollen in all
sediments should be noted again. With that, the pollen assemblages of section LA025 indicate a
shrub tundra vegetation with tree occurrence, characteristic for the "Pre-Sartan" warmer phase
of the Kargin Interstadia in the Taymyr region. Analogous pollen diagrams are published by
Belorusova and Ukraintseva (1980) and Andreeva and Kind (1982) from exposed interstadial
fluvio-lacustrine sediments, dated between 32000 and 24000 yr BP, in river valleys to the
north of the Labaz area. This means that a part of the available radiocarbon datings obtained
from wood material in the section LA025 cannot been used for determination of the age of
Land-Ocean Systems in the Siberian Arctic: Dynamics and History
Pollen assemblages obtained from profile LA022 (Figure 7) indicated warmer climatic
conditions for the accumulation period of this section than we have at present A rich shrubtundra vegetation with open larch and birch woods dominated_ During the formation of zone I
and 3, a more humid climatic character can be assumed_ The pollen assemblages of zone 2
suggested drier conditions_ There was a significant increase of shrub pollen percentage with
dwarf birch dominance_ Tree pollen, including both alder types as well as spores, decreased_ A
small increase of Poaceae and other herbs was observed in the NAP_ The typical xerophyte
pollen of Ephedra was also observed_ The high amounts of redeposited Mesozoic but
apparently Cretaceous pollen in all samples is significant They indicate that glaciogenic
deposits of unit I were strongly eroded and redistributed_ Because all radiocarbon data
indicated ages greater than 46000 yr BP, we suppose that these sediments were likely formed
not later than the first warming phase of the Kargin Interstadial. Without a doubt, active glacier
ice decay took place during this time, leading to a strong activation of erosional processes and
to a rise of accumulation in adjacent lakes_
Site LA025 represents fluvio-Iacustrine (and likely deltaic) sediments which were exposed at
the basis of the 55 - 60 m lake terrace to the east of the Tolton-Pastakh-Yuryakh River mouth
(Figures I and 2)_ Exposed sediments showed a clear bedding with an inclination of about 10°
towards the W -WNW. The lower part of the section consisted of light grey sand interlaminated
by silt and clay with characteristic rust-coloured layer boundaries. Among various
allochthonous plant remains, tree branches were present From 3.6 to 2.8 m depth, layered
sands containing coal detritus and small gravels were interbedded by numerous floating peat
layers. The overlying horizon consisted of sand, silt and clay interbedding with several tree and
shrub remains as well as crushed angular gravels and pebbles. Sub vertical grass roots were
found in the upper two meters. The latter sediments seemed to be influenced by recent or
Holocene slope and soil forming processes. For wood remains from this section, radiocarbon
ages between about 34000 yr and more than 40000 yr BP were recorded including some
inverse data. A dating of 285OO±400 yr BP was obtained from floating peat material at a depth
of 2.8 m. These results indicate that the sediments contained potentially redeposited plant
material, especially wood remains.
The pollen diagram of site LA025 (Figure 8) showed similarities to that of site LA022
(Figure 7). Small percentages of NAP and a dominance of Betula sect. Nanea and Alnaster are
characteristic features. However, in contrast to site LA022, the pollen percentage of trees,
especially of Betula Alba and Alnus, was slightly higher at site LA025. Similarities between
both sites also existed in the composition of NAP and spores. Poaceae and Ericaceae were
found in appreciable amounts, with less Artemisia and Cyperaceae. For other herbs, Asteraceae
and Cichoriaceae were continuously present, and Carophyllaceae, Pedicularis, Dryas and
others less frequently. Spores observed belonged to Bryales, Polypodiaceae and Lycopodium
(especially L. alpinum, less L. pungens, and least of all L. annotium , L. complanatum and L.
appressum). The spore pollen assemblages of zones I and 3 in the diagram correspond to a
shrub tundra vegetation growing under humid and warmer climatic conditions than those of
today. The pollen assemblages of zone 2 indicate the development of an almost pure birchshrub tundra, sparsely distributed, with open larch forest under drier but still warmer climatic
conditions than today. The considerable amounts of redeposited Cretaceous pollen in all
sediments should be noted again. With that, the pollen assemblages of section LA025 indicate a
shrub tundra vegetation with tree occurrence, characteristic for the "Pre-Sartan" warmer phase
of the Kargin Interstadia in the Taymyr region. Analogous pollen diagrams are published by
Belorusova and Ukraintseva (1980) and Andreeva and Kind (1982) from exposed interstadial
fluvio-lacustrine sediments, dated between 32000 and 24000 yr BP, in river valleys to the
north of the Labaz area. This means that a part of the available radiocarbon datings obtained
from wood material in the section LA025 cannot been used for determination of the age of