I. BACKGROUND
Duvanny Yar is the well known stratigraphic key site for late Quaternary deposits in Beringia, the landmass non-glaciated during the late Pleistocene between the Taymyr Peninsula and Alaska [1].
The outcrop is dominated by Middle Weichselian ice-rich permafrost sequences, termed as “Ice Complex” or “Yedoma Suite” [2].
In course of the IPY project #15: Past Permafrost, the aim of this study was to obtain a comprehensive cryolithological characterization of Ice Complex deposits which represent a significant carbon reservoir under climate warming conditions due to permafrost degradation [3].
II. STRATIGRAPHY
Six permafrost profiles along the right bank of the Kolyma river were sampled in summer 2008 (Figures 1). They exposed Eemian lacustrine deposits (profiles DY-02 , DY-03), long sequences of Middle Weichselian Ice Complex deposits (profiles DY-01, DY-05) and Holocene lacustrine and bog deposits in thermokarst depressions (profile DY-04) (Figure 2).
III. MULTIPROXY APPROACH
A multidisciplinary approach of cryolithological methods was applied to obtain data sets of stable isotope composition of ground ice (δ18O, δD), ice contents, grain size and biogeochemical
parameters (TOC, TN, δ13C), mineral density, mass-specific magnetic susceptibility and radiocarbon ages of the sediments (Figures 3-6). Based on density, ice and TOC contents (in wt%), the organic carbon content (in kg TOC per m3) was estimated for the Ice Complex to quantify the carbon pool stored therein.
IV. ICE COMPLEX CHARCTERISTICS
Ice
• Massive to lenticular and layered cryostructures;
thus syngenetic freezing processes
• Mean gravimetric ice content: 55 to 60 wt%
• Huge syngenetic ice wedges:
up to 2.5 m wide and up to 7 m long Grain size
• Uniform polymodal grain size distribution
• Poorly sorted clayey and sandy silt:
Trask sorting co-efficient 3-4
• Two major peaks in fine silt and coarse silt fractions, one minor peak in fine sand fraction
• Magnetic susceptibility mainly from 30 to 60 SI indicating a rather homogenous mineral composition; thus stable sediment source
• Regular transport and accumulation conditions during the whole period of Ice Complex formation Organic carbon
• TOC (0.5 to 2 wt%), TOC/TN (5 to 15), δ13C (-27.4 to -24.6‰); thus organic source from fresh water and subaerial terrestrial environments
• Peaty paleocryosols with higher TOC (>2 wt%) and TOC/TN (>10)
• Estimated mean organic carbon amounts to 16±11 kg*m-3
Figure 3 Sediment records of the composite Ice Complex profiles DY-05 (red diamonds) and DY-01 (black diamonds) including its Holocene top
Figure 4 Parameters for TOC content estimations of Ice Complex deposits. Green marked data in profile DY-01 indicate not measured ice content hence the mean value of 34 wt% was used.
Figure 1 Location of the Yedoma key site
References
[1] Hopkins DM (1982) In: Paleoecologyof Beringia, AcademyPress, NY, London, pp. 3-27.
[2] SherAV (1991) Quaternary International 10-12: 215-222.
[3] Zimov et al. (2006) Science 312: 1612-1613.
[4] Gitermanet al. (1982) In: Paleoecologyof Beringia, AcademyPress, NY, London, pp. 43-73.
[4] Giterman et al. (1982)
Total density (mineral+ice) [g*cm-3]
Bulk density [g*cm-3]
TOC content [kg TOC*m-3]
Altitude [m a.r.l.] Profile DY-05Profile DY-01
Absolute ice content
[wt%]
Figure 2 Cryolithological schemes of the studied profiles
*Contact
sebastian.wetterich@awi.de Alfred Wegener Institute Department of Periglacial Research Potsdam, Germany;
20406080 0 5 10 355 1015 35 -30 -28 -26 -24
25 30 35 40
0 100 200 0 25000 50000
39720 +930/-840 24910 +540/-500
9890± 50
32180 +370 /-350
0 25 50
mean grain size [µm]
20406080 0 5 10 355 1015 35 -30 -28 -26 -24 25
20
15
10
5
0
0 100 200 0 25000 50000
> 46690 38660 +1370/
-1170 41590 +740/-680
40880 +2100/
-1170
0 100
Altitude [m a.r.l.] Profile DY-05Profile DY-01Overlap
Radiocarbon age [a BP]
Grain size distribution [%]
δ13C vs. VPDB
[‰]
TOC / TN TOC [wt%]
Magn. suscept.
[10-8m3*kg-1] Gravimetric ice content [wt%]
Clay Silt Sand
Figure 5 Stable water isotopes of texture ice (open diamonds) and ice wedges (triangle) of the composite Ice Complex profiles DY-05 (red diamonds) and DY-01 (black diamonds) including its Holocene top
-40 -35 -30 -25 -20 -280 -240 -200 -160 0 10 20 30 40 50
24 28 32 36 40
l
2 6 10 14 18
Altitude [m a.r.l.] 22 Profile DY-01Profile DY-05
26 44
δ18O vs. VSMOW
[‰]
δD vs. VSMOW
[‰]
d excess vs. VSMOW
[‰]
Figure 6 Polymodal grain size distribution of the composite Ice Complex profiles DY-05 and DY-01 (n=79)
0 2 4 6
0.1 1 10 100 1000
fin e m id d le c o a rs e fin e m id d le c o a rs e fin e m id d le c o a rs e
Clay Silt Sand
Grain size [μm]
Volume per cent [%]
Permafrost properties of the Yedoma key site at Duvanny Yar
(Kolyma lowland, East Siberia)
Jens Strauß, Sebastian Wetterich* and Lutz SchirrmeisterPlotted without overlap
Reference №0199
20 40 60
2 6 10 14 18 22 26
1 1.5 2 2.5 0 0.51 1.5 2 0 25 50 75 200 400
20 40 60
24 28 32 36 40 44
1 1.5 2 2.5 0 0.51 1.5 2 0 25 50 75 200 400
Plotted without overlap
