The mineralogical composition of calcium and calcium-magnesium carbonate pedofeatures of calcareous soils in the European prairie ecodivision in Hungary

Abstract There is little data on the mineralogy of carbonate pedofeatures in the calcareous soils in Hungary which belong to the European prairie ecodivision. The aim of the present study is to enrich these data. The mineralogical composition of the carbonate pedofeatures from characteristic profiles of the calcareous soils in Hungary was studied by X-ray diffractometry, thermal analysis, SEM combined with microanalysis, and stable isotope determination. Regarding carbonate minerals only aragonite, calcite (+ magnesian calcite) and dolomite (+proto-dolomite) were identified in carbonate grains, skeletons and pedofeatures. The values relating, respectively, to stable isotope compositions (C13, O18) of carbonates in chernozems and in salt-affected soils were in the same range as those for recent soils (latter data reported earlier). There were no considerable differences between the values for the carbonate nodules and tubules from the same horizons, nor were there significant variations between the values of the same pedofeatures from different horizons (BC-C) of the same profile. Thus it can be assumed that there were no considerable changes in conditions of formation. Tendencies were recognized in the changes of (i) carbonate mineral associations, (ii) the MgCO3 content of calcites, (iii) the corrected decomposition temperatures, and (iv) the activation energies of carbonate thermal decompositions among the various substance-regimes of soils. Differences were found in substance-regimes types of soils rather than in soil types

Sulphate and chloride salt efflorescences and their relationships with groundwaters and soils in Hungary

The aim of the present study is a better understanding of the distribution and formation of salt efflorescences by mineralogical examination. Dominant sodium sulphate and sodium chloride surface efflorescences were selected for investigation. 24 samples were collected between 1999 and 2005 from 16 sites. The soil types were solonchak and meadow solonetz.Basic soil and groundwater analyses were performed according to the standard methods. Minerals were determined by X-ray diffractometry and SEM combined with microanalysis. The evaporation experiments were carried out in a Sanyo Versatile 350 HT environmental test chamber.It was concluded that common sulphate salts form rare and unique mineral associations on salt affected soils in Hungary.Comparing the groundwater compositions and the mineral associations of surface efflorescences or that of precipitated evaporites of groundwaters, the conclusion can be drawn that groundwater composition is reflected much better by the mineral association of experimentally precipitated evaporates of the groundwater than by the mineral associations of surface efflorescences. These differences suggest that the soil matrix may have an effect on the crystallization of minerals (e.g. gypsum, thenardite) in the efflorescences. The differences also suggest that in the surface efflorescences the precipitation process does not come to the end in all cases (minerals with high solubility are missing).Concerning the data on groundwater level depths in case of different (sodium carbonate versus sodium sulphate and sodium chloride) efflorescences, there is a tendency of declining groundwater table in the sequence of these soils. This difference can be explained by the difference (increase) in the solubility of various salt minerals.It was recognized that the change in the major component of surface efflorescenes in time (i.e. the sodium carbonate and sodium carbonate chloride versus sodium sulphate efflorescences before and after 1998) can be explained by the decline of the groundwater level and by the decreasing hydromorphic influence in the lowland area during the 19th and 20th century.Finally it can be stated that the presented research — which mainly focused on mineralogical aspects — has contributed to the earlier knowledge on surface salt efflorescences, which was based only on their chemical composition

Geochemical records of a bentonitic acid-tuff succession related to a transgressive systems tract - Indication of changes in the volcanic sedimentation rate

A detailed stratigraphic and facies reconstruction of a bentonitized acid-tuff succession, deposited within the transgressive systems tract of the Upper Miocene-Sarmatian Ser-3 eustatic cycle, at Sajóbábony, northern Hungary, was performed via petrographic, mineralogical and geochemical analyses. The purpose of the work was to analyze the degree of alteration of the volcanogenic sediments, as an indicator of the relative volcanic sedimentation rate. This may have an important role in indicating volcanic periods synchronous with sedimentation or reconstructing the volcanosedimentary paleoconditions. Sample pairs were collected from each bentonite and tuff layer, and, to facilitiate microstratigraphic relations, samples were collected every 10 cm within bentonite layers. Mineralogical analyses were performed by X-ray diffraction and geochemical analyses by inductively coupled plasma-mass spectroscopy. The CaO/KO and Eu/La ratios correlate with each other and with a montmorillonite/X-ray-amorphous phase ratio, reflecting Ca and Eu incorporation associated with devitrification and smectite formation. In accordance with the current literature, these mineralogical and geochemical proxies can be related primarily to the weathering processes. Considering vertical distributions in a sequence-stratigraphic context, the Ca content and Eu/La values show that local peaks and Eu anomalies characteristic of acid tuffs show minima at flooding surfaces (FS). Within a bentonite layer, representing a single transgressive period, the repeated events of dust-tuff accumulations have been determined by KO/CaO and La/Eu peaks, confirmed also by the Eu anomalies in the rare earth element (REE) patterns, thus leading to the conclusion that the level of alteration is closely correlated with the elimination of terrigenous input and a minimum in volcanic sedimentation rate allowing more intensive alteration of the deposited volcanic material. In the case of fine tuff beds, Eu anomalies on REE patterns reflect limited alteration at the bottom and more intensive alteration in the upper parts of the beds, reflecting the effect of infiltration of sea water into the pores

Tectonically controlled Quaternary intracontinental fluvial sequence development in the Nyírség–Pannonian Basin, Hungary

The Quaternary fluvial succession of the Nyírség (NE Hungary), a proximal sub-basin of 4000 km2 in the intracontinental Pannonian Basin, was studied based on log facies analysis. Regional mapping of sequences was established by analysis of fully cored boreholes and high scale local correlations in densely drilled areas. The age of the sequences was determined by correlating the magnetic susceptibility (MS) record of the fully cored boreholes with that of the reference Hungarian boreholes dated paleomagnetically (Dévaványa-1 and Vésztő-1 in Cooke et al., 1979). To give the Hungarian data global perspective they were correlated to the MS curve of the Chinese Loess (Ding et al., 2005) that are in turn correlated with the Marine Isotope Record (Lisiecki and Raymo, 2005 and Gibbard and Cohen, 2008). The ages of the mapped sequence boundaries are 2.62, 2.26, 2.12, 1.22, 1.04, 0.58 and 0.34 Ma respectively and can be related to the transitions from cool to warm conditions. Regional unconformities at 2.26–2.12, 1.22 and 0.58 Ma also coincide with activity maxima of the radiometrically dated Quaternary volcanism. This high frequency of climatically controlled erosive sequence boundaries in the structurally active periods indicates that the sedimentary record of climatic erosion is better expressed in times when structural changes generate instability in the drainage network. The occurrence of packages of regional unconformities in relation to volcanic activity enables the geochronological dating of episodes in the Quaternary compression of the Carpathian–Pannonian region. The role of tectonic control on the climatically induced changes in the drainage network has been explained by a structural development model based on seismic, gravity and magnetic data. The changes in the local paleohydrology were triggered by a compression related elevation of the basement and the associated occurrence of a local transtension-related subsidence