484
Land-Ocean Systems in the Siberian Arctic: Dynamics and History
Results and interpretations
On the basis of the obtained results, four stratigraphic units representing different historical
periods of the Late Quaternary environmental development can be differentiated in the study
area (Figure 2 ).
Unit 1: Glacial sediments
Unit 1 consists of different glaciogenic sediments most probably formed during the Zyryan
(Early Weichselian) stadial. These deposits built up the highest relief levels in the study area.
Their observed thickness reaches a maximum of about 60 m.
The bottom of unit 1 consists of dense dark grey or grey-brown boulder clay with a massive
or fine lens-shaped cryostructure. In places, the horizon was exposed up to a height of 5-7 m
above the modern lake level. Upwards, the boulder clay is overlain by glaciolacustrine
sediments. This horizon consists of grey rhythmically interbedded and partially interiaminated
clay, silt and sand, in parts with gravel and single boulders. The cryostructure of these ice-rich
(more than 50 weight%) deposits is characterized by fine to coarse reticulate networks of ice
lenses typical for perennially frozen lacustrine deposits transformed epigenetic ally into
permafrost under the influence of water migration processes. Such sediments were studied and
sampled during the summer of 1994 in a large thermocirque with a maximum depth of 31 m
(LA08, Figures 1 and 2). The analytic results confirmed a glacio-lacustrine origin: first, all
sediments were characterized by a very low content of organic matter. The total amounts of
C org and N did not exceed 0.12% and 0.08%, respectively. Secondly, the pollen assemblages
of the studied samples were strongly dominated by redeposited Mesozoic and Tertiary pollen
and spores, while Quaternary pollen were found only as single grains. The observed pollen and
spores from the Pleistocene belong to tundra vegetation.
Within unit 1, buried glacier ice bodies were found at two sites (LA024, LA029; Figures 1
and 2) during the field work in 1995. The first (thickness about 8 m) started to become exposed
after an earth slide in a newly activated recent thermocirque located on the SW exposed slope of
glaciogenic sediments (see Figure 2). In the ice body, layers of various ice structures including
characteristic glacier ice crystals could be observed. The stable isotopic composition in this ice
profile ranged from -22.35%0 to -26.90%0 and -172.1%0 to -201.0%0 for 0 18 0 and 02H,
respectively. Towards the end of the field work in 1995, a second buried glacier ice body
became exposed on the shore bank near the stabilized thermocirque of LA08. This glacier ice
was observed from the beach up to an altitude of more than 10m above lake level, and in a
bowl-like thermokarst depression along a deep erosion valley, oriented almost vertically to the
beach (Figure 3). The wall of the thermocirque consisted of dark-grey layered loamy-sandy
deposits with gravel and small boulders, which belong to the upper horizon of unit 1. The
stable isotope composition of ice sampled at the near-surface horizon varied between -24.55%0
and -29.51%0, and -188.3%0 and -225.6%0 for 0 18 0 and 02H, respectively. All values obtained
from the two sites plot on the Meteoric Water Line (Figure 4).
The upper horizon of unit 1 was built up of crudely stratified loamy sands with gravel. These
deposits are interpreted as flow till, probably formed during deglaciation They contained a small
amount of ground ice and were characterized by massive cryostructures. At the surface, these
sediments were under the influence of aeolian processes - boulder pavements were observed.
Unit 2: Sediments of the Kargin Interstadial
Unit 2 represents a complex strata which comprises primarily lacustrine and fluvio-lacustrine
sediments, overlying deposits of unit 1 with an erosional unconformity. These sediments fill
extended depressions within unit 1 as well as erosional forms, developed later within sediments
Land-Ocean Systems in the Siberian Arctic: Dynamics and History
Results and interpretations
On the basis of the obtained results, four stratigraphic units representing different historical
periods of the Late Quaternary environmental development can be differentiated in the study
area (Figure 2 ).
Unit 1: Glacial sediments
Unit 1 consists of different glaciogenic sediments most probably formed during the Zyryan
(Early Weichselian) stadial. These deposits built up the highest relief levels in the study area.
Their observed thickness reaches a maximum of about 60 m.
The bottom of unit 1 consists of dense dark grey or grey-brown boulder clay with a massive
or fine lens-shaped cryostructure. In places, the horizon was exposed up to a height of 5-7 m
above the modern lake level. Upwards, the boulder clay is overlain by glaciolacustrine
sediments. This horizon consists of grey rhythmically interbedded and partially interiaminated
clay, silt and sand, in parts with gravel and single boulders. The cryostructure of these ice-rich
(more than 50 weight%) deposits is characterized by fine to coarse reticulate networks of ice
lenses typical for perennially frozen lacustrine deposits transformed epigenetic ally into
permafrost under the influence of water migration processes. Such sediments were studied and
sampled during the summer of 1994 in a large thermocirque with a maximum depth of 31 m
(LA08, Figures 1 and 2). The analytic results confirmed a glacio-lacustrine origin: first, all
sediments were characterized by a very low content of organic matter. The total amounts of
C org and N did not exceed 0.12% and 0.08%, respectively. Secondly, the pollen assemblages
of the studied samples were strongly dominated by redeposited Mesozoic and Tertiary pollen
and spores, while Quaternary pollen were found only as single grains. The observed pollen and
spores from the Pleistocene belong to tundra vegetation.
Within unit 1, buried glacier ice bodies were found at two sites (LA024, LA029; Figures 1
and 2) during the field work in 1995. The first (thickness about 8 m) started to become exposed
after an earth slide in a newly activated recent thermocirque located on the SW exposed slope of
glaciogenic sediments (see Figure 2). In the ice body, layers of various ice structures including
characteristic glacier ice crystals could be observed. The stable isotopic composition in this ice
profile ranged from -22.35%0 to -26.90%0 and -172.1%0 to -201.0%0 for 0 18 0 and 02H,
respectively. Towards the end of the field work in 1995, a second buried glacier ice body
became exposed on the shore bank near the stabilized thermocirque of LA08. This glacier ice
was observed from the beach up to an altitude of more than 10m above lake level, and in a
bowl-like thermokarst depression along a deep erosion valley, oriented almost vertically to the
beach (Figure 3). The wall of the thermocirque consisted of dark-grey layered loamy-sandy
deposits with gravel and small boulders, which belong to the upper horizon of unit 1. The
stable isotope composition of ice sampled at the near-surface horizon varied between -24.55%0
and -29.51%0, and -188.3%0 and -225.6%0 for 0 18 0 and 02H, respectively. All values obtained
from the two sites plot on the Meteoric Water Line (Figure 4).
The upper horizon of unit 1 was built up of crudely stratified loamy sands with gravel. These
deposits are interpreted as flow till, probably formed during deglaciation They contained a small
amount of ground ice and were characterized by massive cryostructures. At the surface, these
sediments were under the influence of aeolian processes - boulder pavements were observed.
Unit 2: Sediments of the Kargin Interstadial
Unit 2 represents a complex strata which comprises primarily lacustrine and fluvio-lacustrine
sediments, overlying deposits of unit 1 with an erosional unconformity. These sediments fill
extended depressions within unit 1 as well as erosional forms, developed later within sediments