Geology and geochemistry of the near surface sediments of Pornóapáti-Dozmat area

Abstract

In this paper the soil and loose sediment samples of six pedological trenches from the West Hungárián
Pomoapáti-Dozmat forest area were studied. The samples were analysed and they represented mainly
clayey and subordinately, sandy and pebble deposits. The analyses involved granulometric,
microscopical, X-ray and ICP-MS methods. The aim of our research was to obtain information about the
origin of the sedimented matériái, about the mineralogical and geochemical changes, and about the
concentration and movement of the main and trace nutrient elements in the studied forest soil.
The detritic matériái comes from the Palaeozoic and Jurassic greenschists and metamorphosed basic
rocks which outcrop in the nearby-situated Vas-hegy and from similar outcroprng sites on the Austrian
side of the Pinka hydrographic basin. They were transported eastward by a few small water flows during
the last Interstadials of the Würm glaciation. The coarse sediments represent mazbe the riverbed facies,
while the fine grained ones — i.e. the so called "brown earth" — are the floodplain facies of the same
rivulet system. Thus no evidence was found which could prove the existence of a régiónál coarse levél
("Trans-Raba Pebble Cover") and there was alsó no evidence for the aeolian origin of the „brown earth".
The fine grained, Fe-Al rich sediments has suffered a strong differentiation due to the breakdown of
Fe-Mg silicates and feldspars, by the loose of a part of the alkalies and of the Ca, and the synthesis of the
clay minerals. There are signs that the finer clay fraction and the iron hydroxide colloids were
transported downwards. The iron hydroxides förmed limonite crusts and pellets in the lower part of the
soil profiles.