Matskási István (szerk.): A Magyar Természettudományi Múzeum évkönyve 81. (Budapest 1989)

Szendrei, G.: Microscopic study of thin sections from lithogenic soils

RESULTS AND DISCUSSION The micromorphological features observed in the soils under investigation are given in Table 1. The micromorphological investigations were evaluated for each soil from two aspects: 1) what are the main common features found by comparing our data on a particular soil to the generalized characteristics of the soil type as concluded from data from earlier studies; 2) interpretation of the micromorphological investigations from the aspects of soil genetics, based on the relationships established between micromorphological features and their forming processes. Humus-carbonate soil - Data on the micromorphology of lithogenic soils formed on calcareous parent materials are available, these are, however, devoted mainly to rendzina soils (AGUILAR et al. 1978; KASHANSKIÏ, TURSINA & SUKHANOV 1987; KOWALINSKI, LlCZNAR & LlCZNAR 1972; KOWALINSKI 1974, 1978; KUBIENA 1948, 1953,1970; SZABÓ 1974; SZABÓ, MÁRTON & PÁRTAY 1964). Since there are similarities in the formation of these two soil types, the comparison with the generalized micromorphological characteristics obtained from the references will be discussed. In the profile studied the absence of features indicating clay migration and some occurrence of calcitic pedofeatures were in accordance with the generalized micromorphological characteristics. The humus form, type of microstructure, the porphyric related distribution of fine and coarse constituens, the type of voids and b-fabric described in the investigated profile were also observed in some of the referred soils. The interpretation of the micromorphological study from the aspects of soil formation processes indicated the lack of clay migration and the mobilization of calcium-carbonate and ferruginous compounds. The occurrence of calcitic nodules and acicular crystals reflected the mobilization of calcium-carbonate. From solutions supersaturated to Ca- and Mg-ions the formation of large calcite crystals is not feasible and the crystallization of needle-like crystals with wowen arrangement was attributed to the poising effect of relatively high magnesium concentration (FOLK 1974). In Rego Dark Brown soil (Saskatchewan, Canada) pedogenic Mg-bearing calcites were found as elongated crystals or bundles of coalesced fibres (MERMUT & ST. ARNAUD 1981). The acicular crystals with woven arrangement were considered as the first stage of calcareous crust formation in Mollisols (Southern Italy). The occurrence of micritic nodules is supposed to belong to the subsequent stage during which the crystals those had formed in the first stage were again dissolved and recrystallized (MAGALDI 1983). The ferruginous nodules were common in A- and rare in C-horizons indicating hydromorphic influence. The evalution of the characteristics of these nodules indicated a lower degree of hydromorphysm (DOBROVOLSKIÏ, BALABKO & KUZMENKO 1981, MATINYAN 1981, RUDEFORTH 1970, SCHWERTMANN & FANNING 1976, SIMONSON & BOERSMA 1972, VENEMAN, VEPRASKAS & BOUMA 1976; ZAIDEL'MAN, NIKIFOROVA & SANZHAROV 1979). Rendzina soils - In the Hungarian soil classification system the soil type of rendzina is subdivided into three subtypes: black, brown and red clayey rendzina. The micromorphological study of two subtypes (black and red clayey rendzina) is given below.