In 2019, a thermokarst lake located in low-shrub polygonal tundra in the Old Crow Flats (Yukon, Canada) drained catastrophically, forming a 1.9km2 drained basin containing a residual pond covering 32% of the basin and corresponding to the deepest parts (2-3 m) of the former lake. In the south-western part of the basin, the youngest part where bank erosion was strongest, a polygonal network was visible after drainage. In the troughs of the polygonal network, ice-wedge pseudomorphs were found in 2022-2023. Ice-wedge pseudomorphs are thermokarst structures that form by the secondary infilling of sediment in deformed cavities left by the melting of ice wedges. The pseudomorphs that were found formed during the expansion of the former lake and differ greatly in composition from the encompassing sediments. This dataset reports the soil properties of seven pseudomorphs and their encompassing sediments (i.e. lake-bottom sediments) that were unearthed at increasing distance from the southwest shoreline to study their composition and morphology.
