Past freeze and thaw cycling in the margin of the El'gygytgyn crater deduced from a 141 m long permafrost record

Abstract

Abstract. The continuous sediment record from Lake El'gygytgyn in the northeastern Eurasian Arctic spans the last 3.6 Ma and for much of this time permafrost dynamics and lake level changes have likely played a crucial role for sediment delivery to the lake. Changes in the ground-ice hydrochemical composition (δ 18 O, δD, pH, electrical conductivity, Na + , Mg 2+ , Ca 2+ , K + , HCO − 3 , Cl − , SO − 4 ) of a 141 m long permafrost record from the western crater plain are examined to reconstruct repeated periods of freeze and thaw at the lake edge. Stable water isotope and major ion records of ground ice in the permafrost reflect both a synsedimentary palaeo-precipitation signal preserved in the near-surface permafrost (0.0-9.1 m core depth) and a post-depositional record of thawing and refreezing in deeper layers of the core (9.1-141.0 m core depth). These lake marginal permafrost dynamics were controlled by lake level changes that episodically flooded the surfaces and induced thaw in the underlying frozen ground. During times of lake level fall these layers froze over again. At least three cycles of freeze and thaw are identified and the hydrochemical data point to a vertical and horizontal talik refreezing through time. Past permafrost thaw and freeze may have destabilised the basin slopes of Lake El'gygytgyn and this has probably promoted the release of mass movements from the lake edge to the deeper basin as known from frequently occurring turbidite layers in the lake sediment column.

Evidence of multiple thermokarst lake generations from an 11 800‐year‐old permafrost core on the northern Seward Peninsula, Alaska

“…A similar situation has been found near Lake El'gygytgyn, where lateral contact with the adjacent lake and open system freezing have been suggested to explain uniform isotope composition over large parts of a permafrost core (Schwamborn et al . ). Hence, we assume a complex talik system next to our coring location due to the presence of Lake Rhonda until the present time.…”

Reconstructing Permafrost Sedimentological Characteristics and Post-depositional Processes of the Yedoma Stratotype Duvanny Yar, Siberia

“…Sediment samples (n 38) were sieved to separate the 10-50 μm and 51-100 μm fractions. Following Schwamborn et al (2012), Schwamborn et al (2014) the mineral compositions in the 10-50 μm and 51-100 μm grain-size fractions were determined by X-ray phase analysis with a Dron-3M (Shlykov, 1991).…”

DataSheet1.pdf

“…Sediment samples (n 38) were sieved to separate the 10-50 μm and 51-100 μm fractions. Following Schwamborn et al (2012), Schwamborn et al (2014) the mineral compositions in the 10-50 μm and 51-100 μm grain-size fractions were determined by X-ray phase analysis with a Dron-3M (Shlykov, 1991).…”