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

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

Degradation features were also recognized (fragmented and depleted parts) indicating some stress and diminishing iron content as well. Another feature reflecting the mobilization and precipitation of manganese and iron compounds was the presence of nodules. Besides mesosized ferruginous nodules with sharp or clear boundaries, manganiferous nodules were also found and in certain parts they were common. This may be the consequence of more oxidative (or less reductive) conditions in the matrix than the ones present during the formation of ferruginous nodules. In the Bi-horizon the manganiferous hypocoating indicates oxidative environment along the cracks causing the migrating manganese compounds to precipitate, however, the coatings and infillings reflect these conditions in the voids as well. The micromorphological features indicated an intensive joint migration of iron compounds and clay on one hand, and the separate mobilization of iron and manganese compounds (iron and manganiferous nodules, depleted infillings) on the other hand. Erubase soil - The cracking was dominant in A2- and B-horizons which was consistent with the observations of BELLINFANTE at al. (1974) in Vertisols (Southern Spain) revealing that cracks were found below the surface horizons and vughs occurred as well. The b-fabric was generally well developed in Vertisols (NETTLETON & SLEEMAN 1985, NETTLETON, PETERSON & BORST 1983), whereas in the profile investigated by us it was masked or weak. The different varieties of pedoturbation were also common in Vertisols, whereas in the soil profile under discussion they were not found. The ferruginous and manganiferous nodules indicating hydromorphic influence occur in Vertisols (NETTLETON & SLEEMAN 1985) and were characteristic in this case as well. Various generations of ferruginous and manganiferous nodules were found. The black, mesosized manganiferous nodules with sharp boundaries reflect a short (not exceeding one day in duration) period of saturation by water (VENEMAN, VEPRASKAS & BOUMA 1976). The ferruginous nodules indicate long waterlogging. The interpretation based on their micromorphological characteristics indicate that these generations of nodules were formed under a slighter (brown, brownish black colour, mesosize with sharp boundary) and a stronger (yellowish brown colour, diffuse boundary) hydromorphic influence, respectively. The nodules were formed by impregnation of the matrix. The absence of illuviated clay coatings was considered to be characteristic for Vertisols due to the repeated pressure and soil movements (BELLINFANTE et al. 1974), but clay coatings were also described from some Vertisols (NETTLETON & SLEEMAN 1985). Their occurrence was interpreted as a relict feature. In the soil profile studied the ferruginous clay infillings were rare in A- and were common in B-horizons. The aggregate type is angular blocky or apedal which was also observed in other Vertisols (BELLINFANTE et al. 1974, NETTLETON & SLEEMAN 1985). The c/f related distribution was porphyric which had also been found in some Vertisols (BELLINFANTE et al. 1974, NETTLETON & SLEEMAN 1985, NETTLETON, PETERSON & BORST 1983). Only a part of the micromorphological features typical for Vertisols could be observed in the soil profile under discussion. The interpretation of the micromorphological features from the aspects of soil formation indicated various degrees of hydromorphic influence (ferruginous and manganiferous nodules) and clay mobilization especially in B-horizon.