Loess/paleosol/cryogenic formation and structure near the northern limit of loess deposition, East European Plain, Russia

Uncertainty about the geological processes that deposited syngenetically frozen ice‐rich silt (yedoma) across hundreds of thousands of square kilometres in central and northern Siberia fundamentally limits our understanding of the Pleistocene geology and palaeoecology of western Beringia, the sedimentary processes that led to sequestration of hundreds of Pg of carbon within permafrost and whether yedoma provides a globally significant record of ice‐age atmospheric conditions or just regional floodplain activity. Here, we test the hypotheses of aeolian versus waterlain deposition of yedoma silt, elucidate the palaeoenvironmental conditions during deposition and develop a conceptual model of silt deposition to clarify understanding of yedoma formation in northern circumpolar regions during the Late Pleistocene. This is based on a field study in 2009 of the Russian stratotype of the ‘Yedoma Suite’, at Duvanny Yar, in the lower Kolyma River, northern Yakutia, supplemented by observations that we have collected there and at other sites in the Kolyma Lowland since the 1970s. We reconstruct a cold‐climate loess region in northern Siberia that forms part of a vast Late Pleistocene permafrost zone extending from northwest Europe across northern Asia to northwest North America, and that was characterised by intense aeolian activity. Five litho‐ and cryostratigraphic units are identified in yedoma remnant 7E at Duvanny Yar, in ascending stratigraphic order: (1) massive silt, (2) peat, (3) stratified silt, (4) yedoma silt and (5) near‐surface silt. The yedoma silt of unit 4 dominates the stratigraphy and is at least 34 m thick. It is characterised by horizontal to gently undulating subtle colour bands but typically lacks primary sedimentary stratification. Texturally, the yedoma silt has mean values of 65 ± 7 per cent silt, 15 ± 8 per cent sand and 21 ± 4 per cent clay. Particle size distributions are bi‐ to polymodal, with a primary mode of about 41 μm (coarse silt) and subsidiary modes are 0.3–0.7 μm (very fine clay to fine clay), 3–5 μm (coarse clay to very fine silt), 8–16 μm (fine silt) and 150–350 μm (fine sand to medium sand). Semidecomposed fine plant material is abundant and fine in‐situ roots are pervasive. Syngenetic ice wedges, cryostructures and microcryostructures record syngenetic freezing of the silt. An age model for silt deposition is constructed from 47 pre‐Holocene accelerator mass spectrometry (AMS) 14C ages, mostly from in‐situ roots and from three optically stimulated luminescence (OSL) ages of quartz sand grains. The 14C ages indicate that silt deposition extends from 19 000 ± 300 cal BP to 50 000 cal BP or beyond. The OSL ages range from 21.2 ± 1.9 ka near the top of the yedoma to 48.6 ± 2.9 ka near the bottom, broadly consistent with the 14C age model. Most of the yedoma silt in unit 4 at Duvanny Yar constitutes cryopedolith (sediment that has experienced incipient pedogenesis along with syngenetic freezing). Mineralised and humified organic remains dispersed within cryopedolith indicate in...

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“…Compiled from Hopkins (), Velichko et al . (, , ), Liu (), Dodonov (), Frechen et al . () and Vriend et al .…”

Section: Interpretation and Discussionmentioning

confidence: 97%

Palaeoenvironmental Interpretation of Yedoma Silt (Ice Complex) Deposition as Cold‐Climate Loess, Duvanny Yar, Northeast Siberia

Murton

Goslar

Edwards

et al. 2015

Permafrost & Periglacial

124

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“…In our model we do not consider the presence of thermokarst lakes outside Beringia. Permafrost expansion into the northern mid latitudes of Eurasia and North America during the Last Glacial Maximum also resulted in ground ice accumulation in many regions as indicated by occurrence of fossil ice wedge networks, as well as organic carbon storage in soils and loess sediments [ Murton et al , 2003; Velichko et al , 2006]. Possibly, ground ice in these more southern regions was relatively enriched in δ D H2O compared to North Siberian ice wedge ice and could have contributed to further moderation of lake δ D CH4 upon thaw.…”

Section: Discussionmentioning

confidence: 99%

Using the deuterium isotope composition of permafrost meltwater to constrain thermokarst lake contributions to atmospheric CH₄ during the last deglaciation

et al. 2012

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[1] Thermokarst lakes are thought to have been an important source of methane (CH 4 ) during the last deglaciation when atmospheric CH 4 concentrations increased rapidly. Here we demonstrate that meltwater from permafrost ice serves as an H source to CH 4 production in thermokarst lakes, allowing for region-specific reconstructions of dD CH4 emissions from Siberian and North American lakes. dD CH4 reflects regionally varying dD values of precipitation incorporated into ground ice at the time of its formation. Late Pleistocene-aged permafrost ground ice was the dominant H source to CH 4 production in primary thermokarst lakes, whereas Holocene-aged permafrost ground ice contributed H to CH 4 production in later generation lakes. We found that Alaskan thermokarst lake dD CH4 was higher (À334 AE 17‰) than Siberian lake dD CH4 (À381 AE 18‰). Weighted mean dD CH4 values for Beringian lakes ranged from À385‰ to À382‰ over the deglacial period. Bottom-up estimates suggest that Beringian thermokarst lakes contributed 15 AE 4 Tg CH 4 yr À1 to the atmosphere during the Younger Dryas and 25 AE 5 Tg CH 4 yr À1 during the Preboreal period. These estimates are supported by independent, top-down isotope mass balance calculations based on ice core dD CH4 and d 13 C CH4 records. Both approaches suggest that thermokarst lakes and boreal wetlands together were important sources of deglacial CH 4 .Citation: Brosius, L. S., K. M. Walter Anthony, G. Grosse, J. P. Chanton, L. M. Farquharson, P. P. Overduin, and H. Meyer (2012), Using the deuterium isotope composition of permafrost meltwater to constrain thermokarst lake contributions to atmospheric CH 4 during the last deglaciation,

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“…13), more or less simultaneously with the cryoturbation. This could reflect the early Weichselian glaciation with aeolian loess sedimentation on the east European Russian plains (the Sevsk loess) further south (Velichko et al 2006b). To the west, this could correspond to aeolian sand at the beginning of the 100–90 kyr BP glaciation (Kjær et al 2006).…”

Section: Discussion Of the Geological Historymentioning

confidence: 99%

River sections at the Byzovaya Palaeolithic site – keyholes into the late Quaternary of northern European Russia

Heggen¹,

Svendsen²,

Mangerud³

2009

Boreas

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Heggen, H. P., Svendsen, J. I. & Mangerud, J. 2009: River sections at the Byzovaya Palaeolithic site – keyholes into the late Quaternary of northern European Russia. Boreas, 10.1111/j.1502‐3885.2009.00109.x. ISSN 0300‐9483. The geological history of northern European Russia over the past two glacial cycles is reconstructed from the stratigraphy in river bluffs along the upper reaches of the Pechora River. From a till bed near the base of the sections it is inferred that the Barents–Kara Ice Sheet covered the area during the late Saalian (MIS 6). After deglaciation, and prior to the last interglacial, the area was flooded by an ice‐dammed lake, suggesting that the Pechora Basin was blocked by a subsequent ice advance at the very end of the Saalian. Ice‐wedge casts and periglacial sediments reflect a pronounced cooling with formation of permafrost during the Early Weichselian (MIS 5d). An overlying thick sequence of shallow lacustrine sediments accumulated in the ice‐dammed Lake Komi, formed by the advancing Barents–Kara Ice Sheet 80–100 kyr BP (MIS 5b?). Following drainage of the lake, many of the older formations were eroded by fluvial activity. Animal remains found together with palaeolithic artefacts within debrisflow sediments at the base of one of the incised gullies yielded radiocarbon ages around 28 000–30 000 14C yr BP (33–34 cal. kyr BP). The surface with traces of human activities was subsequently covered by aeolian sediments representing the northern extension of the European belt of periglacial coversand that accumulated in the cold and dry climate during the late Weichselian (MIS 2). The results of this work confirm the assumption that the last shelf‐centred ice sheet that covered this part of Russia occurred during the late Saalian (MIS 6), but that this glaciation was followed by a younger and less extensive ice advance that has not been described before. There are no indications that local glaciers originating in the Ural Mountains reached the Pechora River valley throughout the last two glacial cycles.

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Loess/paleosol/cryogenic formation and structure near the northern limit of loess deposition, East European Plain, Russia

Cited by 63 publications

References 4 publications

Palaeoenvironmental Interpretation of Yedoma Silt (Ice Complex) Deposition as Cold‐Climate Loess, Duvanny Yar, Northeast Siberia

Palaeoenvironmental Interpretation of Yedoma Silt (Ice Complex) Deposition as Cold‐Climate Loess, Duvanny Yar, Northeast Siberia

Using the deuterium isotope composition of permafrost meltwater to constrain thermokarst lake contributions to atmospheric CH₄ during the last deglaciation

River sections at the Byzovaya Palaeolithic site – keyholes into the late Quaternary of northern European Russia

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Loess/paleosol/cryogenic formation and structure near the northern limit of loess deposition, East European Plain, Russia

Cited by 63 publications

References 4 publications

Palaeoenvironmental Interpretation of Yedoma Silt (Ice Complex) Deposition as Cold‐Climate Loess, Duvanny Yar, Northeast Siberia

Palaeoenvironmental Interpretation of Yedoma Silt (Ice Complex) Deposition as Cold‐Climate Loess, Duvanny Yar, Northeast Siberia

Using the deuterium isotope composition of permafrost meltwater to constrain thermokarst lake contributions to atmospheric CH4 during the last deglaciation

River sections at the Byzovaya Palaeolithic site – keyholes into the late Quaternary of northern European Russia

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Using the deuterium isotope composition of permafrost meltwater to constrain thermokarst lake contributions to atmospheric CH₄ during the last deglaciation