Characteristics of permafrost-affected soil in a cliff in the central part of the Polish Baltic coastal zone

Purpose

The study aimed to characterise a fossil permafrost-affected (Stagnic Fluvisol Relictiturbic) soil, occurring in a cliff in the central part of the Polish Baltic coastal zone near Orzechowo (54° 35.664′ N, 16° 54.123′ E).

Materials and methods

The soil was sampled at 22 points and analysed using standard procedures in soil science. After standard preparation, disturbed and undisturbed soil samples were made subject to laboratory analyses concerning their physical and chemical properties. Radiocarbon dates and pollen analysis results were also obtained for the selected soil samples.

Results and discussion

The permafrost-affected soil lies beneath a fossil Dystric Histic Stagnosol, which is covered by about 8 m of aeolian deposits. The radiocarbon age of the Dystric Histic Stagnosol was 3061 ± 60 cal. years BP, and that of the Stagnic Fluvisol Relictiturbic 10,161 ± 110 cal. years BP. However, the results of pollen analysis suggest rejuvenation of the obtained dates. The Stagnic Fluvisol Relictiturbic developed in the marginal part of a body of water, from fluvioglacial and aeolian sands deposited on grey glacial till. The mineral substrates of the soil are moderately and poorly sorted sands and silt loam in the bottom part of the profile. This fine-textured material has been moved to the upper parts of the profile due to the impact of the water freezing and thawing cycles in the permafrost active layer. The observed microstructures on quartz grain (0.5–1.0 mm) surfaces, including conchoidal fractures, breakage blocks and v-shaped pits, are typical for periglacial soils. The fossil Stagnic Fluvisol Relictiturbic is poor in total iron. The observed vertical distribution of free iron oxides suggests their displacement in the permafrost active layer. Soil organic matter was found to be moderately or strongly humified, which is not typical for permafrost-affected soils and can suggest its allochthonous, probably alluvial, character.

Conclusions

The studied Stagnic Fluvisol Relictiturbic developed at the close of the Pleistocene in the marginal part of a body of water. It constitutes a sequence of horizons of varied thickness and abundance in organic matter. The influence of a periglacial environment is reflected in morphology of the soil (cryoturbations) and some chemical properties and partially in microstructures observed on quartz grain surfaces.

     

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