Abstract
Six soils located within the Polish Carpathians, developed on calcium carbonate–rich sedimentary parent materials and representing various reference groups, were investigated in order to detect the lithic discontinuity. We propose using a multidirectional approach to assess the lithic discontinuity in these soils, one that includes grain size distribution, geochemical composition, heavy mineral content and micromorphology, supported by a traditional soil survey. A further aim of this process was to identify the possible admixture of allochthonous material of aeolian origin. The studied soils presented lithic discontinuities mostly at the contact of underlying calcium carbonate–rich coarsegrained slope deposits with the overlaying colluvium layer having a lower content of rock fragments. The significant changes in grain size distribution, especially in the silt and sand content, as well as high Uniformity Values and partially, high Lithological Discontinuity Index values, confirmed the occurrence of a lithic discontinuity in all studied soils. High heterogeneity in the soil profiles was also confirmed by the distribution of the major oxides; however, their distribution did not clearly indicate the lithic discontinuity. The most visible distinctions were noted from CaO content, which resulted from the deposition of carbonate-free materials (aeolian silts) and their mixing with the calcium carbonate–rich parent material. Furthermore, the analysis of heavy mineral content confirmed the allochthonous origin of the upper (and in some cases also the middle) parts of all profiles, which was manifested by the presence of highly weathering-resistant minerals such as zircon, epidote and various types of garnets. The micromorphological features of some of the studied soils showed distinctiveness within the soil profile, manifested by changes in b-fabric pattern, the occurrence and distribution of secondary carbonate and the coarse and fine coarse and fine ratio. Based on the high content of silt within the upper and middle parts of the soils, the content of Hf and Zr, as well as the higher content of weathering-resistant minerals, admixture of aeolian silt could be considered in some of the studied soils, yet with weak character. However, the dominance of minerals typical for metamorphic and igneous rocks suggested that the supply of aeolian silt was associated with loess covers rather than local sedimentary material.
Highlights
The origin and development of heterogeneous soils has been the subject of many studies (Ahr et al 2012; Butler 1959; Kowalska et al 2016; Lorz and Phillips 2006; Schaetzl 1998; Waroszewski et al 2013, 2015)
We propose using a multidirectional approach to assess the lithic discontinuity in these soils, one that includes grain size distribution, geochemical composition, heavy mineral content and micromorphology, supported by a traditional soil survey
We propose using a multidirectional approach toward assessment of the heterogeneity of the soil, including grain size distribution, coarse fragments, geochemical composition, analysis of heavy minerals and micromorphology and supported by a traditional soil survey, for identification of lithic discontinuities in calcium carbonate-rich soil in the Polish Carpathians (South Poland)
Summary
The origin and development of heterogeneous soils has been the subject of many studies (Ahr et al 2012; Butler 1959; Kowalska et al 2016; Lorz and Phillips 2006; Schaetzl 1998; Waroszewski et al 2013, 2015). Ahr et al (2012) described a lithologically and chronologically distinct stratigraphic unit, separated by a lithic discontinuity between sandy material weathered from sandstone bedrock and the underlying argillic horizon in a subtropical climate. Lithic discontinuities have been seen at the junction of the eluvial (sandy loam, loam, or silt loam textural class) and illuvial horizons (clay, clay loam, or sandy clay loam textural class) in studies carried out by Bockheim (2016) in various soils of the United States
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