Gábor Újvári

Dimensional complexity of the EEG in subcortical stroke - A case study

The conventional electrophysiological methods used for the analysis of the functional characteristics of the nervous system are not able to grasp its non-linear and random features. Of the methods based on the application of chaos-theory the correlation dimension analysis can be used to quantify the complexity of the analyzed signal, such as the electroencephalogram (EEG). The new version (point-correlation dimension, PD2) was used in this study, which is more accurate than the other, currently used algorithms. The purpose of the present investigation was to compare the sensitivity of the methods based on chaos-theory with the traditional electrophysiological ones in a case when no apparent abnormality was present as judged on the basis of this latter methodology. The PD2 was calculated from the EEG recorded in 13 healthy control subjects and in a patient who suffered a small subcortical stroke 2 years prior to the investigation and who was free of neurological symptoms at the time of recording. Compared to that seen in the control group, in the Z-score maps of the scalp distribution of the PD2, a marked asymmetry was seen and the absolute PD2 values showed a low-dimensional area in the parietal region, ipsilateral to the stroke. A relative decrease of the gamma band was found in the frequency power spectra in the same area. It is suggested that the additional information extracted from the EEG by non-linear analysis may increase the sensitivity of electrophysiological methods for detecting brain pathology.

Late Pleistocene variations of the background aeolian dust concentration in the Carpathian Basin: an estimate using decomposition of grain-size distribution curves of loess deposits

Aeolian dust deposits can be considered as one of the most important archives of past climatic changes. Alternating loess and paleosol strata display variations of the dust load in the Pleistocene atmosphere. By using the observations of recent dust storms, we are able to employ Late Pleistocene stratigraphic datasets (with accurate chronological framework) and detailed granulometric data for making conclusions on the atmospheric dust load in the past. Age-depths models, created from the absolute age data and stratigraphic interpretation, allow us to calculate sedimentation rates and dust fluxes, while grain-size specifies the dry-deposition velocity, i.e. the atmospheric residence time of mineral particles. Thus, the dust concentration can be expressed as the quotient of the dust flux and gravitational settling velocity. Recent observations helped to clarify the mechanisms behind aeolian sedimentation and the physical background of this process has nowadays been well established. Based on these two, main contrasting sedimentary modes of dust transport and deposition can be recognised: the short suspension episodes of the coarse (silt and very fine sand) fraction and the long-range transport of a fine (clay and fine silt) component. Using parametric curve fitting the basic statistical properties of these two sediment populations can be revealed for Pleistocene aeolian dust deposits, as it has been done for loess in Hungary. As we do not have adequate information on the magnitude and frequency of the Pleistocene dust storms, conclusions could only be made on the magnitude of continuous background dust load. The dust concentration can be set in the range between 1100 and 2750 μg/m3. These values are mostly higher than modern dust concentrations, even in arid regions. Another interesting proxy of past atmospheric conditions could be the visibility, being proportional to the dust concentration. According to the known empirical dust concentration visibility equations, its value is around 6.5 to 26 kilometres.

Clay mineralogy of red clay deposits from the central Carpathian Basin (Hungary): implications for Plio-Pleistocene chemical weathering and palaeoclimate

Josip KOVAČEVIĆ*, Maja KOVAČEVIĆ, Vera CESAR, Georg DREZNER, Alojzije LALIĆ, Hrvoje LEPEDUŠ, Zvonimir ZDUNIĆ, Zorica JURKOVIĆ, Krešimir DVOJKOVIĆ, Zorana KATANIĆ, Vlado KOVAČEVIĆ Agricultural Institute Osijek, Osijek, Croatia Department of Biology, Josip Juraj Strossmayer University of Osijek, Osijek, Croatia Faculty of Agriculture in Osijek, Josip Juraj Strossmayer University of Osijek, Osijek, Croatia

Two possible source regions for central Greenland last glacial dust

Dust in Greenland ice cores is used to reconstruct the activity of dust-emitting regions and atmospheric circulation. However, the source of dust material to Greenland over the last glacial period is the subject of considerable uncertainty. Here we use new clay mineral and <10 µm Sr–Nd isotopic data from a range of Northern Hemisphere loess deposits in possible source regions alongside existing isotopic data to show that these methods cannot discriminate between two competing hypothetical origins for Greenland dust: an East Asian and/or central European source. In contrast, Hf isotopes (<10 µm fraction) of loess samples show considerable differences between the potential source regions. We attribute this to a first-order clay mineralogy dependence of Hf isotopic signatures in the finest silt/clay fractions, due to absence of zircons. As zircons would also be absent in Greenland dust, this provides a new way to discriminate between hypotheses for Greenland dust sources.

Ice-volume-forced erosion of the Chinese Loess Plateau global Quaternary stratotype site

The International Commission on Stratigraphy (ICS) utilises benchmark chronostratigraphies to divide geologic time. The reliability of these records is fundamental to understand past global change. Here we use the most detailed luminescence dating age model yet published to show that the ICS chronology for the Quaternary terrestrial type section at Jingbian, desert marginal Chinese Loess Plateau, is inaccurate. There are large hiatuses and depositional changes expressed across a dynamic gully landform at the site, which demonstrates rapid environmental shifts at the East Asian desert margin. We propose a new independent age model and reconstruct monsoon climate and desert expansion/contraction for the last ~250 ka. Our record demonstrates the dominant influence of ice volume on desert expansion, dust dynamics and sediment preservation, and further shows that East Asian Summer Monsoon (EASM) variation closely matches that of ice volume, but lags insolation by ~5 ka. These observations show that the EASM at the monsoon margin does not respond directly to precessional forcing.A basic requirement for reconstructing past environmental change is accurate understanding of sediment age. Here, the authors show that the interpretation of a benchmark archive in China has been inaccurate, and that ice volume primarily controls desert dynamics, sediment preservation, and precipitation at the site.

Coupled European and Greenland last glacial dust activity driven by North Atlantic climate

Significance Atmospheric dust is a major component of climate change. However, the relationship between glacial continental dust activity and abrupt centennial–millennial-scale climate changes of the North Atlantic is poorly known. Recent advances in high-precision radiocarbon dating of small gastropods in continental loess deposits provide an opportunity to gain unprecedented insights into dust variations and its major drivers at centennial–millennial scales from a near-source dust archive. Here, we show that Late Quaternary North Atlantic temperature and dustiness in Greenland and Europe were largely synchronous and suggest that this coupling was driven via precipitation changes and large-scale atmospheric circulation. Centennial-scale mineral dust peaks in last glacial Greenland ice cores match the timing of lowest Greenland temperatures, yet little is known of equivalent changes in dust-emitting regions, limiting our understanding of dust−climate interaction. Here, we present the most detailed and precise age model for European loess dust deposits to date, based on 125 accelerator mass spectrometry 14C ages from Dunaszekcső, Hungary. The record shows that variations in glacial dust deposition variability on centennial–millennial timescales in east central Europe and Greenland were synchronous within uncertainty. We suggest that precipitation and atmospheric circulation changes were likely the major influences on European glacial dust activity and propose that European dust emissions were modulated by dominant phases of the North Atlantic Oscillation, which had a major influence on vegetation and local climate of European dust source regions.

Recurring mass movements on the Danube's bank at Dunaszekcső (Hungary) observed by geodetic methods

Abstract. In September 2007 a geodetic network based on GPS measurements, precise levelling and continuous borehole tilt measurements was established for surface displacement monitoring on the high bank of the River Danube at Dunaszekcső where a serious landslide began to develop at that time. The landslide took place on February 12, 2008. After rapid, enormous movements, which resulted in significant subsidence (8–10 m) and lateral displacements (4–5 m) on the high bank at Dunaszekcső and the emergence of a peninsula consisting of clastic material in the Danubes bed, the deformation rates significantly dropped. This observation was explained by the secondary metastable equilibrium of the moving blocks at that time. However, our subsequent geodetic data clearly showed that slow post-event movements (mainly subsidence, 0.5–1.0 cm/month) on both the northern and southern sliding blocks have been occurring for the last two years, which means that the sliding blocks did not reach an equilibrium in the mentioned period. At the same time, measurements on our extended geodetic network in the second half of 2010 referred to a possible southward spread of sliding (southern part of the Vár Hill) in the near future. Later on (spring 2011), field observations were also indicative of the initiation of movements on the southern part of the Vár Hill as predicted by the geodetic measurements. The areal extent of the block becoming unstable closely corresponds with the danger zone assigned by GPS observations.

Origin and weathering of landslide material in a loess area: a geochemical study of the Kulcs landslide, Hungary

Geochemical characteristics of sediments are responses to physical and chemical alteration in landslides. However, consequences of in situ interactions associated with landslides are difficult to distinguish from those related to long-term weathering in young soft sediments such as loess. In this study, geochemical characteristics of the Kulcs landslide in Hungary are studied to identify the provenance of the loess–paleosol–red clay sequence and geochemical signatures that can potentially be attributed to the effects of landsliding. Results indicate that sliding is largely initiated by the lithological changes within the landslide body. Sediments above the sliding zone closely resemble the non-slipped Pleistocene old loess deposits from Hungary. It is also confirmed that the sliding zone develops in old paleosols in the loess sequence and red clays at its base which are all characterized by the enrichment of Al, K, Na, H2O and considerable depletion in Ca and Mg associated with carbonates. Altogether, these geochemical characteristics indicate that chemical weathering trend of unconsolidated landslide sediments is slightly modified by the redistribution of carbonates and decomposition of plagioclase. It is assumed that the distribution of Mn and Ba is modified by the water–sediment interaction in the landslide.

Editorial: Aeolian deposition and Earth surface systems

mospheric circulation, and climate conditions (Liu, 1985; Liu and Ding, 1998; Sun, 2002; Stevens et al., 2013; Smalley et al., 2014). In order to improve the understanding of the dynamics of Earth surface systems, the International Symposium on Aeolian Deposition in Earth History (ISADEH) was held between 12th and 15th October 2015 at the University of Chinese Academy of Sciences, Beijing (Fig. 1). The symposium was organized by the Loess Focus Group of International Union for Quaternary Research (INQUA), the Loess

Sr-Nd-Hf Isotopic Analysis of <10 mg Dust Samples: Implications for Ice Core Dust Source Fingerprinting: Sr-Nd-Hf ISOTOPES IN DUST

Combined Sr-Nd-Hf isotopic data of two reference materials (AGV-1/BCR2) and 50, 10, and 5 mg aliquots of carbonate-free fine grain (<10 lm) separates of three loess samples (Central Europe/NUS, China/BEI, USA/JUD) are presented. Good agreement between measured and reference Sr-Nd-Hf isotopic compositions (ICs) demonstrate that robust isotopic ratios can be obtained from 5 to 10 mg size rock samples using the ion exchange/mass spectrometry techniques applied. While 87Sr/86Sr ratios of dust aluminosilicate fractions are affected by even small changes in pretreatments, Nd isotopic ratios are found to be insensitive to acid leaching, grain-size or weathering effects. However, the Nd isotopic tracer is sometimes inconclusive in dust source fingerprinting (BEI and NUS both close to ENd(0) –10). Hafnium isotopic values (<10 lm fractions) are homogenous for NUS, while highly variable for BEI. This heterogeneity and vertical arrays of Hf isotopic data suggest zircon depletion effects toward the clay fractions (<2 lm). Monte Carlo simulations demonstrate that the Hf IC of the dust <10 lm fraction is influenced by both the abundance of zircons present and maturity of crustal rocks supplying this heavy mineral, while the <2 lm fraction is almost unaffected. Thus, EHf(0) variations in the clay fraction are largely controlled by the Hf IC of clays/ heavy minerals having high Lu/Hf and radiogenic 176Hf/177Hf IC. Future work should be focused on Hf IC of both the <10 and <2 lm fractions of dust from potential source areas to gain more insight into the origin of last glacial dust in Greenland ice cores.