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

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

Black rendzina - Some of the micromorphological features of the soil under discussion are in accordance with the generalized micromorphological characteristics of rendzinas compiled from former studies i.e. frequent calcareous rock fragments among the coarse constituens, rare or absent clay coatings. The other micromorphological features are not characteristic for all of the black rendzinas, but they occur in some of these soils as e.g. humus form (KUBIENA 1948,1953,1970), vughs (AGUILAR et al. 1978), undifferentiated or crystallicb-fabric (KASHANSKIÏ, TURSINA & SUKHANOV 1987, KOWALINSKI 1974,1978), porphyricc/f related distribution (BREWER, SLEEMAN & FOSTER 1983), ferruginous nodules and coatings (KOWALINSKI 1978). Except for the vicinity of calcareous rock fragments the absence of secondary carbonate forms was also noted (KASHANSKIÍ, TURSINA & SUKHANOV 1987). In the soil under investigation the b-fabric of the fine material and the pedological features do not indicate a considerable mobilization of clay, and of iron- manganese and calcareous compounds. Calcitic pedological features occur only close to the calcareous rock fragments. As for the contacts between the rock fragments and the soil matrix three cases can be distinguished: - calcitic coating on rock fragments with gradual transition to soil matrix impregnating the latter to some extent, - calcitic coating on rock fragments attached to soil matrix, - rock fragments without calcitic coating being either closely attached to the soil matrix or separated from it by cracks. In the upper horizons the ferruginous nodules are rare. Ferruginous coatings and inilllings were more often found in calcareous rock fragments. Red clayey rendzina - The following characteristics of terra rossa can be found in the profile under discussions: peptized and flocculated ferrihydroxide (and oxyhydroxide, oxide) in the ground mass and features resulted of its mobilization (ferruginous clay coatings and infillings) as well as various forms of ferruginous (and manganiferous) nodules. In the investigated profile, and especially in its B2-horizon the ferruginous clay infillings are dominant. The considerable accumulation of clay in terra rossa was already observed by MERMUT (1978) and VERHEYE & STOOPS (1974) by means of soil micromorphology. Its degradation due to swelling and shrinking in mediterranean terra rossa was also indicated. The features arising from degradation were found in red clayey rendzina as well. In addition, depletion features which can be explained by diminishing iron content. Beside the fragmentation of infillings and coatings the following features attributed to the effect of shrinking and swelling by MERMUT (1978), and VERHEYE & STOOPS (1974) were also found: - nodules in the upper part of the profile originating from the subsoil due to pedoturbation, - neostrians along hard skeletons, - developed plasmic fabric (skel-, vo-, in-, mo-, ma-, omnisepic) - dense network of planar voids. The above mentioned micromorphological features were not observed in the soil involved in the present study. The matrix of the red clayey rendzina consists of ferruginous clay. In addition, its mobilized forms were also found (ferruginous clay infillings and coatings). This mobilized red clay can move as deep as the D-horizons.