The origin and transformation of soil lamellae in calcareous and non-calcareous loess soils in the Central European loess belt – A case study from southern Poland

Abstract

Loess in Europe is heterogeneous due to differences in paleoenvironmental conditions during sedimentation and pedogenesis. In many regions of Europe, including southern Poland, loess accumulation was followed by the leaching of carbonates followed by clay translocation, which is typical in silty soils in humid climates. Loess soils in the temperate climate zone are characterized by the presence of well-developed or well-preserved microfabrics of different origin but with similar morphology, among which lamellae can be distinguished. Lamellae commonly occur in loess soils; however, detailed studies focused on their origin and evolution are lacking. The main aim of the present study was to determine the origin and transformation of lamellae both in calcareous and non-calcareous loess soils in the Central European loess belt, using an example from southern Poland. The following three hypotheses were tested: (1) decalcification of the upper part of loess soils is a necessary condition for soil lamellae formation, while frost action is not a key factor shaping their morphology and properties in the Central European loess belt, (2) occurrence of carbonate in the lower part of calcareous loess soils inhibits lamellae formation, (3) soil lamellae are transformed due to bioturbation and shrinking-swelling processes in both calcareous and non-calcareous loess soils. The obtained results indicate that decalcification of the upper part of calcareous loess soils enables the translocation of clay particles and lamellae formation. Field observations and micromorphological analysis indicate that the presence of carbonate limits the development of soil lamellae and constitutes a barrier to deeper clay translocation in loess soils. This finding suggests a pedogenic origin of lamellae in the loess soils of southern Poland. Soil lamellae show a number of signs indicating their mechanical degradation due to swelling and shrinking, bioturbation, and dissolution driven by eluviation and redox processes. The progressive evolution of lamellae leads to an enhancement of their expression in the illuvial Bt and transitional BC horizons.