480
Land·Ocean Systems in the Siberian Arctic: DYTUlmics and History
southern surroundings of Labaz Lake. These profiles represent sediments of relatively young
accumulation terraces. In addition, deposits of different geomorphological levels were
investigated by core drilling within the key section ,a,. Altogether, 20 profiles up to 7 m depth
were drilled.
Study methods
As a basic method for the investigation of permafrost profiles, the "frozen ground facial
analysis" (Katasonov, 1978) was used. This method is based on the relationship between the
cryogenic structure of sediments, as well as on other cryogenic phenomena within sedimentary
complexes, and the geocryological conditions at the time of sediment accumulation and
freezing. Using this method, permafrost sequences can be stratified and information on the
climatic conditions during syngenetic permafrost formation can be obtained (Romanovsky,
1978). Samples were taken for manifold analyses at all study sites. In this publication, results
from radiocarbon dating, palynological investigations and selected results from stable isotope
analyses of ground ice are presented and discussed.
The material which was dated consisted of various plant remains, preserved in permafrost:
mainly peat, peaty soil and wood (the remains of trees and shrubs), and occasionally grass
roots, twigs and/or seeds. The 14C activities were measured in the AWl-Potsdam (lab. no.
indicated as AWl) and in the Leipzig (LZ) laboratories by liquid scintillation counting (LSC),
using Packard Tri-Carb 2560 TRlXL spectrometers in both cases. The 14C ages are given as
conventional ages (Stuiver and Polach, 1977; Geyh and Schleicher, 1990), i. e. the ages -
given in ,yr BP' (years before present, i.e. 1950) - were calculated on the basis of the measured
activity using a 14C half-life of 5568 years. The activity was corrected for isotopic fractionation
by normalizing 013C value to -25%0.
In order to minimize contamination of the sample material, the evidently autochthonous plant
material was removed manually at first. Afterwards, all samples were treated with diluted
NaOH (0.5 mol., 80°C) to extract (allochthonous, migrating) humic acids (Shore et al., 1995)
and then with diluted HCI (0.5 mol., 80°C) to remove possible traces of carbonates. The
washed and dried (neutralized) organic residue of each sample was converted into benzene (3
ml) in the standard manner (Polach et aI., 1972). The radiocarbon ages and 013C-values of
samples from Labaz Lake area determined in the AWl-Potsdam and in the Leipzig laboratories
are compiled in Table 2. In addition, some AMS dating of radiocarbon material from selected
samples were carried out at the Leibniz Laboratory of the University Kiel. These results are
shown in Table 3.
Samples for isotopic studies were taken in the field and stored and transported in 30 ml
polyethylene bottles. Measurements of 0 18 0 values were carried out at the Alfred Wegener
Institute Bremerhaven (A. Mackensen) and measurements of 02H at the Freie University Berlin
(K. Friedrichsen).
Standard methods (maceration using HCI, H2S04 with acetolysis and separation in gravity
liquid by centrifuge) were used for preparing the pollen samples. The results are presented in
percentage pollen diagrams including: (i) the ratio of four groups: I - arboreal pollen (AP) of
trees, 2 - AP of shrubs, 3 -herbaceous pollen (NAP), 4 -spores; (ii) the dominant pollen and
spores as a percentage of the sum of Quaternary pollen and spores; and (iii) the redeposited preQuaternary pollen and spores based on the total pollen and spores sum. A zonation of the
diagrams was done by visual inspection.
Land·Ocean Systems in the Siberian Arctic: DYTUlmics and History
southern surroundings of Labaz Lake. These profiles represent sediments of relatively young
accumulation terraces. In addition, deposits of different geomorphological levels were
investigated by core drilling within the key section ,a,. Altogether, 20 profiles up to 7 m depth
were drilled.
Study methods
As a basic method for the investigation of permafrost profiles, the "frozen ground facial
analysis" (Katasonov, 1978) was used. This method is based on the relationship between the
cryogenic structure of sediments, as well as on other cryogenic phenomena within sedimentary
complexes, and the geocryological conditions at the time of sediment accumulation and
freezing. Using this method, permafrost sequences can be stratified and information on the
climatic conditions during syngenetic permafrost formation can be obtained (Romanovsky,
1978). Samples were taken for manifold analyses at all study sites. In this publication, results
from radiocarbon dating, palynological investigations and selected results from stable isotope
analyses of ground ice are presented and discussed.
The material which was dated consisted of various plant remains, preserved in permafrost:
mainly peat, peaty soil and wood (the remains of trees and shrubs), and occasionally grass
roots, twigs and/or seeds. The 14C activities were measured in the AWl-Potsdam (lab. no.
indicated as AWl) and in the Leipzig (LZ) laboratories by liquid scintillation counting (LSC),
using Packard Tri-Carb 2560 TRlXL spectrometers in both cases. The 14C ages are given as
conventional ages (Stuiver and Polach, 1977; Geyh and Schleicher, 1990), i. e. the ages -
given in ,yr BP' (years before present, i.e. 1950) - were calculated on the basis of the measured
activity using a 14C half-life of 5568 years. The activity was corrected for isotopic fractionation
by normalizing 013C value to -25%0.
In order to minimize contamination of the sample material, the evidently autochthonous plant
material was removed manually at first. Afterwards, all samples were treated with diluted
NaOH (0.5 mol., 80°C) to extract (allochthonous, migrating) humic acids (Shore et al., 1995)
and then with diluted HCI (0.5 mol., 80°C) to remove possible traces of carbonates. The
washed and dried (neutralized) organic residue of each sample was converted into benzene (3
ml) in the standard manner (Polach et aI., 1972). The radiocarbon ages and 013C-values of
samples from Labaz Lake area determined in the AWl-Potsdam and in the Leipzig laboratories
are compiled in Table 2. In addition, some AMS dating of radiocarbon material from selected
samples were carried out at the Leibniz Laboratory of the University Kiel. These results are
shown in Table 3.
Samples for isotopic studies were taken in the field and stored and transported in 30 ml
polyethylene bottles. Measurements of 0 18 0 values were carried out at the Alfred Wegener
Institute Bremerhaven (A. Mackensen) and measurements of 02H at the Freie University Berlin
(K. Friedrichsen).
Standard methods (maceration using HCI, H2S04 with acetolysis and separation in gravity
liquid by centrifuge) were used for preparing the pollen samples. The results are presented in
percentage pollen diagrams including: (i) the ratio of four groups: I - arboreal pollen (AP) of
trees, 2 - AP of shrubs, 3 -herbaceous pollen (NAP), 4 -spores; (ii) the dominant pollen and
spores as a percentage of the sum of Quaternary pollen and spores; and (iii) the redeposited preQuaternary pollen and spores based on the total pollen and spores sum. A zonation of the
diagrams was done by visual inspection.