Concentration of the main soluble ions in the composite wedges of the Upper Sand unit of the Batagay megaslump

Syngenetic composite wedges CW-10, CW-11, CW-12, CW-13, CW-14, and CW-15 were discovered in the Upper Sand unit of the Batagay megaslump, located 10 kilometers southeast of Batagay settlement. The goal of this work is to investigate the composition of ions in composite wedges in order to determine their formation characteristics. The ion composition of composite sand-ice wedges 10–15 from the upper sand is dominated by sulfate anions; their content reaches 372 mg/L. The content of chlorides is high – up to 94 mg /L, the ratio of chloride anions to sulfates reaches 2.7. Among the cations, calcium stands out—up to 172 mg/L and sodium up to 117 mg/L. The content of magnesium cations is up to 115 mg/L. The measurements were performed using a Stayer ion chromatograph. The average EC values in sand-ice wedges are: No. 10 – 407 mSm, No. 11 – 742 mSm, No. 12 – 583 mSm, No. 14 – 783 mSm, and No. 15 – 696 mSm. The average sodium cation content in composite wedges is: No. 10 – 22 mg/L, No. 11 – 63 mg/L, No. 12 – 28 mg/L, No. 14 – 57 mg/L, No. 15 – 35 mg/L. Average values of calcium cation content in sand-ice wedges: No. 10 – 0.42 mg/L, No. 11 – 89 mg/L, No. 12 – 63 mg/L, No. 14 – 92 mg/L, No. 15 – 98 mg/L. Average values of chloride anion content in sand-ice wedges: No. 10 – 23 mg/L, No. 11 – 48 mg/L, No. 12 – 41 mg/L, No. 14 – 51 mg/L, No. 15 – 35 mg/L. Average values of sulfate anion content in sand-ice wedges: No. 10 – 27 mg/L, No. 11 – 104 mg/L, No. 12 – 105 mg/L, No. 14 – 128 mg/L, No. 15 – 64 mg/L. Using the ionic composition of composite wedges as a geochemical tracer to study the problem of the genesis and formation processes of composite wedges allows us to obtain additional evidence of the nature of sand-ice wedges and the conditions of their formation. The chemical composition of wedges located in the Upper Sand unit was influenced by continental aerosols and slope suprapermafrost waters. The most significant difference in the ionic composition of composite wedges from the simultaneously accumulating ice wedges of the Batagay yedoma is the predominance of sulfate anions; their content (up to 372 mg/L) is one and even two orders of magnitude higher than in the ice of most yedoma wedges. In general, the ionic composition of composite sand-ice wedges differs significantly from the ionic composition of the Batagay yedoma ice wedges. Composite sand-ice wedges were formed with the active participation of slope processes and slope suprapermafrost waters.

permafrost, composite wedge, Late Pleistocene, macroelements, cryogeochemistry, mineralization, cations and anions, Upper sand unit, Batagay crater, northern Yakutia