Matskási István (szerk.): A Magyar Természettudományi Múzeum évkönyve 83. (Budapest 1991)

Szendrei, G.: Contribution to the micromorphology of the brown forest soils in Hungary

lows: these are "a series of lamellae of clay separated by bands of unmodified soil material...". Its formation is connected with a colloid chemical Liesegang phenomenon. These soils are generally formed on non-calcareous sandy parent materials. In the A-horizon of the soil studied the related distribution was monic, in some zones (with the extent of 1000-2000 u,m) grain cutans occurred and the related distribution were chitonic or gefuric. In the B-horizon the grain cutans are more frequent as well as the zones with chitonic, gefuric or phorphyric related distribution (Fig. 4) were more extended. Consequently, the micromorphological features belonging to the "kovárvány" were the occurrence of grain cutans. Besides the coatings on the skeletons, clay could form bridges between them and infillings of packing voids leading to the zones with gefuric or porphyric related distribution. Acidic, non-podzolic brown forest soil (Velem, Kőszeg Mts, W Hungary) - Information on the weathering processes can be obtained from the distribution of rock fragments in the profile. Besides the fragments of sericite-phyllite its separated parts, i. e. sericite bundles and quarz fields could be found, too. The number of rock fragments desreased from the BC- to A-horizon. In the A-horizon the relative amount of quartz fields increased, as compared to other fragments. This could be explained by the relative accumulation of the more resistent minerals in comparison to the weatherable minerals, parts of the rocks. The above-mentioned facts indicated more and more intesive weathering in horizons from C to A Ferruginous mottles on the sericite bundles were observed as well. The rock fragments are directly attached to the soil groundmass or separated from it by cracks. The b-fabric indicated preferred orientation only in the BC2- and BC-horizons, which probably could be attributed to the weathering of sericite bundles. Clay coatings occurred in the whole profile, whereas clay infillings were more frequent in the B-horizon. The fragments of the coatings and infillings could be observed in the Bi-, B2- and especially in the BC-horizon. In these soils the clay mobilization was not considered to be feasible due to the strong coagulating effect of trivalent aluminium- and iron ions released in the strongly acidic environment. The occurrence of the preferred orientation in the fine material and of the clay coatings and infillings in some horizons could be explained by the weathering of sericite bundles. Ferruginous and manganiferous nodules were common in the soil studies. The later were more frequent, especially in the Ai-, Bi-, BC-horizons. The ferruginous mottles were attached to the rock fragments in the deeper horizons. The manganiferous nodules with sharp boundaries indicated a very weak hydromorphic influence (VENEMAN, VEPRASKAS & BOUMA 1976, VEPRASKAS & BOUMA 1976). Comparing these data to the former studies on a profile (Mátra Mts, NE Hungary) formed on hidroandesite (RÓZSAVÖLGYI & STEFANOVITS 1960) the occurrence of rock fragments, the signs of intensive weathering and the presence of ferruginous nodules were common micromorphological features in both profiles. A considerable difference was the occurrence of clay coatings, infillings in the soils involved in the present study. They were absent in the soil studied formerly by RÓZSAVÖLGYI & STEFANOVITS (1960). Considering the micromorphological investigations on this soil type in other countries attention should be paid to the following findings. VAN RAST, DE CONINCK & LANGOHR (1983) also supposed that the clay mobilization and migration are not