2.1. Study area
The study area is the Nałęczów Plateau (East Poland) which covers 49608 ha (Figure 1).
The area is covered by loess patches which were mainly deposited during the Vistulian Glaciation ( ca. 50 000 BP to 15 000/12 000 BP). These loess patches are separated by river valleys where the loess cover is absent (Maruszczak, 1991). The thickness of the loess reaches values of 10 to 20 m in the eastern part and up to 30 m in the western part of the region (Harasimiuk, 1987).
Peat with a mean thickness of 3 m, covered by alluvial soils with a mean thickness of 2.3 m, is found in the river valleys of the study area (e.g. Bałaga & Maruszczak, 1981; Urban & Mikosz, 1996; Superson et al., 2003, 2016).
The loess belt covers a Pleistocene sediment complex made up of glacigenic deposits (glacial tills, sands and gravels, clayey loams, clays) from the Odranian (Saale 1) and the Sanian (Elsterian) Glaciation (Harasimiuk & Henkiel, 1978; Pożaryski et al., 1994). The bedrock of the Nałęczów Plateau consists of Upper Maastrichtian (opoka, marly opoka, marl) and Palaeogene (limestone, gaize and carbonate sandstone) rocks (Pożaryska, 1967; Harasimiuk, 1980).
Vast surfaces of this loess plateau have CDs that are a typical element of the landscape of the Nałęczów Plateau (Figure 1). CDs are shallow and barely visible in loess landscape micro landforms, infilled by soil-sediment sequences (Figure 2). Moreover, the Nałęczów Plateau is dissected by main river valleys (Bystra, Ciemięga) and also small river valleys (Grodarz, Czechówka) as well as many erosion-denudation valleys and gully systems (Figure 1). The average density of the gully network is 2.48-10 km per km2 in the western part of the region, while in the eastern part it does not exceed 2 km per km2 (Gawrysiak & Harasimiuk, 2012). The relative heights in the region reach 40–50 m and maximally 90 m in the western part of the region.
The loess of the Nałęczów Plateau is overlain by Luvisols in different stages of erosion, Colluvisols in CDs and dry valley bottoms as well as Fluvisols in valley bottoms.