THE NATURE OF CYCLIC STRUCTURE OF THE ICE COMPLEX, EAST SIBERIA

Dating of ancient permafrost is essential for understanding permafrost stability and interpreting past climate and environmental conditions over Pleistocene timescales but faces substantial challenges to geochronology.Here, we date permafrost from the world&#8217;s largest retrogressive thaw slump at Batagay in the Yana Upland, East Siberia (67.58 &#176;N, 134.77 &#176;E). The slump headwall exposes four generations of ice and sand-ice (composite) wedges that formed synchronously with permafrost aggradation. The stratigraphy differentiates into a Lower Ice Complex (IC) overlain by a Lower Sand Unit, an Upper IC and an Upper Sand Unit. Two woody beds below and above the Lower Sand Unit represent the remains of two episodes of taiga forest development prior to the Holocene forest. Thus, the ancient permafrost at Batagay potentially provides one of the longest terrestrial records of Pleistocene environments in western Beringia.We apply four dating methods to the permafrost deposits to disentangle the chronology of the Batagay permafrost archive &#8211; optically-stimulated luminescence (OSL) dating of quartz and post-infrared-stimulated luminescence (pIR-IRSL) dating of feldspar as well as accelerator mass spectrometry-based Cl-36/Cl dating of wedge ice and radiocarbon dating of organic material.The age information obtained so far indicates that the Batagay permafrost sequence is discontinuous and that the Lower IC developed well before MIS 7, the overlying Lower Sand Unit formed during MIS 6, and the Upper IC and the Upper Sand Unit formed both during MIS 3-2.Additional sampling for all dating approaches presented here took place in spring 2019, and is part of ongoing research to enhance the geochronology of the exceptional palaeoenvironmental archive of the Batagay megaslump.

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3D ground-penetrating radar imaging of ice complex deposits in northern East Siberia

Geophysics ◽

10.1190/geo2015-0129.1 ◽

2016 ◽

Vol 81 (1) ◽

pp. WA195-WA202 ◽

Cited By ~ 7

Author(s):

Stephan Schennen ◽

Jens Tronicke ◽

Sebastian Wetterich ◽

Niklas Allroggen ◽

Georg Schwamborn ◽

...

Keyword(s):

Ground Penetrating Radar ◽

Structural Model ◽

Late Quaternary ◽

The Arctic ◽

Field Site ◽

East Siberia ◽

Borehole Data ◽

3D Gpr ◽

Ground Penetrating ◽

Ice Complex

Ice complex deposits are characteristic, ice-rich formations in northern East Siberia and represent an important part in the arctic carbon pool. Recently, these late Quaternary deposits are the objective of numerous investigations typically relying on outcrop and borehole data. Many of these studies can benefit from a 3D structural model of the subsurface for upscaling their observations or for constraining estimations of inventories, such as the local carbon stock. We have addressed this problem of structural imaging by 3D ground-penetrating radar (GPR), which, in permafrost studies, has been primarily used for 2D profiling. We have used a 3D kinematic GPR surveying strategy at a field site located in the New Siberian Archipelago on top of an ice complex. After applying a 3D GPR processing sequence, we were able to trace two horizons at depths below 20 m. Taking available borehole and outcrop data into account, we have interpreted these two features as interfaces of major lithologic units and derived a 3D cryostratigraphic model of the subsurface. Our data example demonstrated that a 3D surveying and processing strategy was crucial at our field site and showed the potential of 3D GPR to image geologic structures in complex ice-rich permafrost landscapes.

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A multimethod dating study of ancient permafrost, Batagay megaslump, east Siberia

Quaternary Research ◽

10.1017/qua.2021.27 ◽

2021 ◽

pp. 1-22

Author(s):

Julian B. Murton ◽

Thomas Opel ◽

Phillip Toms ◽

Alexander Blinov ◽

Margret Fuchs ◽

...

Keyword(s):

Northern Hemisphere ◽

Organic Material ◽

Radiocarbon Dating ◽

Optically Stimulated Luminescence ◽

East Siberia ◽

Mis 3 ◽

Infrared Stimulated Luminescence ◽

Palaeoenvironmental Conditions ◽

Ice Complex

Abstract Dating of ancient permafrost is essential for understanding long-term permafrost stability and interpreting palaeoenvironmental conditions but presents substantial challenges to geochronology. Here, we apply four methods to permafrost from the megaslump at Batagay, east Siberia: (1) optically stimulated luminescence (OSL) dating of quartz, (2) post-infrared infrared-stimulated luminescence (pIRIR) dating of K-feldspar, (3) radiocarbon dating of organic material, and (4) 36Cl/Cl dating of ice wedges. All four chronometers produce stratigraphically consistent and comparable ages. However, OSL appears to date Marine Isotope Stage (MIS) 3 to MIS 2 deposits more reliably than pIRIR, whereas the latter is more consistent with 36Cl/Cl ages for older deposits. The lower ice complex developed at least 650 ka, potentially during MIS 16, and represents the oldest dated permafrost in western Beringia and the second-oldest known ice in the Northern Hemisphere. It has survived multiple interglaciations, including the super-interglaciation MIS 11c, though a thaw unconformity and erosional surface indicate at least one episode of permafrost thaw and erosion occurred sometime between MIS 16 and 6. The upper ice complex formed from at least 60 to 30 ka during late MIS 4 to 3. The sand unit above the upper ice complex is dated to MIS 3–2, whereas the sand unit below formed at some time between MIS 4 and 16.

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Ground-ice stable-isotope paleoclimatology at the Batagay megaslump, East Siberia

10.5194/egusphere-egu2020-3748 ◽

2020 ◽

Author(s):

Thomas Opel ◽

Sebastian Wetterich ◽

Hanno Meyer ◽

Julian Murton

Keyword(s):

Stable Isotope ◽

Isotope Composition ◽

Middle Pleistocene ◽

Formation Processes ◽

East Siberia ◽

Ground Ice ◽

Frozen Ground ◽

Winter Climate ◽

Study Region ◽

Ice Complex

In recent years, permafrost ground ice (i.e. ice wedges and pore ice) has been frequently utilized as a paleoclimate archive for the Late Pleistocene and Holocene, mainly using stable isotopes from water as proxies for local air temperatures. Due to their formation processes (frost cracking in winter and crack infilling mainly with snowmelt in spring), ice wedges have a unique winter seasonality, whereas pore ice integrates summer or annual precipitation.The world&#8217;s largest retrogressive thaw slump at Batagay in the Yana Upland, East Siberia (67.58 &#176;N, 134.77 &#176;E), provides unique access to Late and Middle Pleistocene permafrost formations usually deeply buried in the frozen ground. The Batagay megaslump exposes syngenetic ice wedges and composite wedges (ice&#8211;sand wedges) along with pore ice in four cryostratigraphic units: (1) the Lower Ice Complex, (2) the Lower Sand, (3) the Upper Ice Complex, and (4) the Upper Sand.Here, we present ground-ice stable-isotope data from all four units. This dataset is accompanied by precipitation stable-isotope values from winter snowpack and summer rain as a first stable-isotope framework for this region.The high continentality of the study region with &#8211; extremely low winter temperatures &#8211; is clearly reflected by the stable-isotope composition for ice wedges from the Upper Ice Complex (MIS 3) and nearby Holocene ice wedges. Both are much more depleted than for any other ice-wedge study site in East Siberia. The ice wedges from the Lower Ice Complex are likely the oldest ice wedges (>0.5 Ma) ever analyzed isotopically and also point to very cold winter climate during formation. Stable-isotope signatures of composite wedges and pore ice are less distinctive and require detailed studies of formation processes and seasonality.

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