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Quaternary International 240 (2011) 52e61

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Quaternary International

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The late Quaternary loess record of Tokaj, Hungary: Reconstructingpalaeoenvironment, vegetation and climate using stable C and N isotopes andbiomarkers

Ann-Kathrin Schatz a,*, Michael Zech b,c, Björn Buggle b, Sándor Gulyás d, Ulrich Hambach c,Slobodan B. Markovi�c e, Pál Sümegi d, Thomas Scholten a

aChair of Physical Geography and Soil Science, Institute of Geography, University of Tübingen, Rümelinstraße 19-23, D-72074 Tübingen, Germanyb Soil Physics Department, University of Bayreuth, D-95440 Bayreuth, GermanycChair of Geomorphology, University of Bayreuth, D-95440 Bayreuth, GermanydDepartment of Geology and Palaeontology, University of Szeged, 6722 Szeged, Egyetem u.2., HungaryeChair of Physical Geography, University of Novi Sad, Trg Dositeja Obradovi�ca 3, 21000 Novi Sad, Serbia

a r t i c l e i n f o

Article history:Available online 20 October 2010

* Corresponding author.E-mail address: ann.schatz@gmx.de (A.-K. Schatz)

1040-6182/$ e see front matter � 2010 Elsevier Ltd adoi:10.1016/j.quaint.2010.10.009

a b s t r a c t

Large areas of Southeast Europe are covered by Pleistocene loess deposits with interbedded palaeosollayers, reflecting interglacials or -stadials. These loess-palaeosol sequences are valuable terrestrialarchives for continuous palaeoclimatic and palaeoenvironmental information. In recent years, thetraditional paradigm of treeless full-glacial palaeoenvironments has increasingly been called intoquestion, as there is palynological, anthracological and malacological evidence for the continuouspresence of trees from loess-palaeosol sequences in the Carpathian Basin. This paper aims at contributingto this discussion by applying biogeochemical, geophysical and sedimentological methods to a lateQuaternary loess-palaeosol profile at Tokaj, NE Hungary. Previous studies at the same location havefocused on molluscs and charcoal, while this study concentrated on stable C and N isotopes and lipidbiomarkers. Long-chain n-alkanes (C23eC33), which form major constituents of plant leaf waxes, havesuccessfully been used as biomarkers over the last years and allow for a reconstruction of palae-ovegetation based on the differentiation of grassland vs. shrubs and trees. Stable carbon isotopes wereused to further differentiate between C3 and C4 palaeovegetation, and stable N isotopes to reconstruct theN cycle and climatic variations. Magnetic susceptibility (MS), organic carbon and grain size distribution,which may serve as proxies for e.g. the intensity of pedegenesis, weathering and palaeowind strength,were measured to complement the biogeochemical results and to establish a pedoe and biostratigraphy.

Although the results do not agree in every detail with previous studies, there are surprising matchesand similarities in the data. Alkane and stable N isotopic data indicate that, pedogenesis occurred underproductive, fertile steppe-grasslands, probably in an intensified seasonal climate, and during reducedsedimentation. Two short treeless-steppe periods were found between 26 and 12 ka BP. However,periods characterised by a cooler climate in which trees and shrubs expanded were also found. Thisinterpretation is also supported by previous mollusc data that provide evidence for several periods offavourable conditions for tree growth.

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1. Introduction

In order to better understand the impact of climate changeon regional ecosystems, detailed knowledge about past climateand vegetation changes obtained by highly resolved spatial andtemporaldata is essential (Solomonetal., 2007). TheCarpathianBasin,characterised bywidespread,multiple loess-palaeosol sequences, has

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often been regarded as the missing link for the understanding of thelate Quaternary history of Europe, as its geomorphic setting e a lowbasin surrounded by mountain chains e allows for a preservation ofthe sedimentary record. Having been unglaciated during cold stages(Denton and Hughes, 1981), the Carpathian Basin has recently beenproposed to be the most probable location for cold-stage refugia ofmeso- and thermophilous flora and fauna during the last full-glacial(w37e16 ka BP) (Willis et al., 2000). The theory of trees surviving insmall pockets at microclimatically favourable locations is opposed tothe paradigm of treeless grass steppe palaeoenvironments, which is

A.-K. Schatz et al. / Quaternary International 240 (2011) 52e61 53

mainly based on pollen records (e.g. Willis et al., 1995; Alfano et al.,2003; Huntley et al., 2003). However, this traditional picture hasalso beenquestionedby recent results fromanthracological (charcoal;Sümegi and Rudner, 2001; Willis et al., 2000; Willis and van Andel,2004), molluscan (Sümegi and Hertelendi, 1998; Sümegi andKrolopp, 2002), and palaeontological studies (Stewart and Lister,2001; Musil, 2003), as well as by palaeoclimatic simulations (Barronand Pollard, 2002). All these studies propose a “steppe-tundra” or“open parkland” palaeoenvironment instead.

The study site at Tokaj, NE Hungary (Fig. 1), is a potential loca-tion for such an ecosystem where favourable conditions may haveprevailed during the late Quaternary. Tokaj is situated at the borderof the low mountain region and the alluvial plain, where change-able morphology allows diverse microclimatic spots to evolve.Previous palaeoenvironmental studies in this area, mainly focusingon molluscs and charcoal, have been carried out by Sümegi andHertelendi (1998) and Sümegi and Rudner (2001). Results pointto spatially and temporally highly variable palaeoenvironmentalconditions, but also to the potential presence of a small tree ref-uge during very cold stages. Further insights into the late Quater-nary vegetation history of the area could be provided by newgeochemical proxies as e.g. stable isotopes and biomarkers.

Soil organic carbon, which is mainly derived from plants, hasa d13C value that closely reflects that of plant biomass. With almostno change of the isotopic signal during incorporation into thesediment, stable carbon isotopic records provide valuable palae-ovegetational evidence regarding C3/C4 vegetation and havesuccessfully been used by Hatté et al. (1998, 1999), Liu et al. (2005),Zech (2006) and Zech et al. (2009b) to reconstruct past environ-mental and climatic conditions from loess organic matter.

In contrast to stable carbon isotopes, stable nitrogen isotopeshave hardly been applied in palaeoecology to date (Zech et al.,2007). Generally, the natural abundance of 15N in soils reflects thesumof all isotopic fractionationprocesseswithin theN cycle in soils,with N losses generally causing 15N enrichment. Hence, Eshetu andHögberg (2000) and Zech et al. (submitted) have used d15N to

Fig. 1. Map of Hungary showing borders, geomorphology, major rivers and cities. The studyblack triangle) in the transition zone of the low mountain region and the alluvial plain.

determine the state of N-cycling in order to detect N lossesinduced by climate and land use changes. Other studies have linkedd15N variation to global or regional climate, showing that depletedd15N values are correlated with low temperatures and increasedprecipitation and vice versa (Amundson et al., 2003; Aranibar et al.,2004; Terwilliger et al., 2008).

A third methodological approach of this study are long-chainedn-alkaneswith carbon atomnumbers between 25 and 33 (C25eC33).These lipids are constituents of plant leaves (Kolattukudy, 1976),which are deposited in topsoils by litter fall and subsequentlyincorporated and preserved in the sediment (Cranwell, 1981;Lichtfouse et al., 1994; Bourbonniere, 1997; Lichtfouse, 1998;Schefuß et al., 2003; Wiesenberg et al., 2004). As different vegeta-tion types reveal distinct alkane composition patterns (‘finger-print’), n-alkanes have first been used to distinguish betweenlacustrine and terrestrial matter in lake sediments (Cranwell, 1973;Ficken et al., 2002; Schwark et al., 2002; Hanisch et al., 2003) and,more recently, to reconstruct vegetation changes (grass vs. trees)from terrestrial sediments (Xie et al., 2002; Zhang et al., 2006; Baiet al., 2009; Zech et al., 2009b, 2010; ).

This paper presents a multidisciplinary study using stablecarbon and nitrogen isotopes, as well as n-alkanes. A combinationof these novel palaeoecological proxies has been applied for thefirst time in this area. The results complement previous studiesaimed at reconstructing the late Quaternary history of NE Hungaryand provide valuable insights into the vegetation history of NEHungary during the last 70,000 years.

2. Study area

2.1. Geographical setting and modern climate

Tokaj is situated in the northeast of the Carpathian Basin (Fig. 1),a region of approximately 300,000 km2 that is surrounded bymajormountain ranges (Carpathian Mts., Alps, Dinaric Mts.). During thelast ice age, the climate was cold and dry (Hertelendi et al., 1992;

site at Tokaj (NE Hungary) is located at the banks of the river Tisza (48�07’ N, 21�24’ E;

A.-K. Schatz et al. / Quaternary International 240 (2011) 52e6154

Willis et al., 1995). Hungary remained unglaciated (Denton andHughes, 1981), but extensive permafrost extended across centralEurope and parts of Hungary were in a zone of discontinuouspermafrost (Pécsi, 1961; Bell and Walker, 2005; Kovács et al.,2007). The area around Tokaj is considered of highest palae-oenvironmental significance, as it may have been an importantrefuge for deciduous and coniferous trees during the last ice agedue to a favourable microclimate on the hill slopes (Sümegi andHertelendi, 1998; Sümegi and Rudner, 2001). Today, NE Hungaryis part of the continental climate zone (Dfb after Köppen’s classi-fication, warm summer subtype), with a large seasonal tempera-ture variance (mean January temperature:�3 �C; mean July: 20 �C)and mean annual precipitation of w 600 mm (summer maximum)(Peel et al., 2007).

The study site itself is situated on the eastern slopes of KopaszHill (100 m a.s.l., 48�07’ N, 21�24’ E), in the southernmost part ofthe Tokaj Mountains, where the Bodrog discharges into the Tisza,forming extensive floodplains. Kopasz Hill is a Samartian (MiddleMiocene) stratovolcano built up of pyroxene andesite and dacitelava tongues (16.4 km2) that have partly been eroded and subse-quently been covered by 15e20 m of Pleistocene loess (Kerényi,1994; Sümegi and Hertelendi, 1998). There are 11 well-describedloess outcrops around Kopasz Hill (Sümegi, 1996, 2005). Theprofile at Patkó stone quarry, on the eastern slopes of the moun-tain, was chosen because several detailed studies have beencarried out there (Sümegi and Hertelendi, 1998; Willis et al., 2000;Rudner and Sümegi, 2001; Sümegi and Rudner, 2001; Sümegi andKrolopp, 2002; ). At Patkó quarry, two well-developed palaeosolsand three loess layers are exposed on top of an approximately40 m high dacite wall that has been mined until several years ago.The loess walls on top have been partly removed and cut back-wards due to the mining activities, but the remaining loess hasstayed unaltered.

2.2. Stratigraphy and chronology

The Patkó quarry outcrop and the results of sedimentological,geochronological (radiocarbon) and geochemical investigationshave been described in detail by Sümegi and Rudner (2001) andSümegi and Hertelendi (1998). Very generally (see Fig. 2), thelowermost yellow-brown, unstratified loess layer has been datedto 70e50 ka BP based on vertebrate remains found in similar

Fig. 2. Profile sketch and schematic stratigraphy of the palaeosol-loess section at Patkó stone14C ages after Sümegi and Hertelendi, 1998): Recent soil e Upper loess layer (26e12 ka BP) e(40e32 ka BP) e Lower palaeosol (50e40 ka BP) e Lower loess layer (70e50 ka BP) e Bedrocoverlapping sections for sampling (Section A and B).

stratigraphic positions at other locations (Pinczés, 1954, 1987).Accordingly, this layer accumulated during the first cold and dryphase of the Weichselian. The lower palaeosol, a dark brown soilwith high clay content, was presumably formed under humid,warm conditions (50e40 ka BP, according to uncalibrated radio-carbon ages) and probably corresponds to theMende Upper 2 (MF2)soil, a Hungarian palaeosol that has frequently been described inthe literature. Between 40e32 ka BP, loess was deposited again. Ontop of this intermediate loess layer, the upper palaeosol developed,a reddish-brown, charcoal-rich horizon, which may correspond tothe Mende Upper 1 soil (MF1; 32e26 ka BP). This reddish-brownpalaeosol is overlain by a bleached, whitish layer with high silicacontent, which has been interpreted as remnants of a podzol.On top of this white layer, a thin charcoal layer can be found,primarily consisting of burned Picea (spruce) pieces. This charcoallayer has been dated to 28e26 ka BP and interpreted as the result ofextensive natural wildfires occurring after pedogenesis ceasedand the climate became extremely dry. Between 26e12 ka BP,loess deposition resulted in the formation of the upper loess layer.The recent soil is only weakly developed, which might be due tosoil erosion and open cast mining in the quarry. Furthermore, theuppermost 50e75 cm are affected by recent bioturbation.

3. Material & methods

3.1. Sampling

Due to the topology and to safety concerns, the profile had to besampled in two separate, but overlapping sections (A and B, seeFig. 2). After removing at least the first 30 cm of the front in order toavoid sampling weathered sediment and biological material, thesections were prepared and fully described with regard to colour,density, texture and occurrence of fossil and modern roots,carbonate mycelia and charcoal remains. For laboratory analyses,mixed samples were taken in 25 cm intervals, stored in plastic bagsand dried at 40 �C for several days.

3.2. Granulometry

Sub-samples of 2 g sediment were decalcified (2 M HCl),dispersed with sodium-hexa-metaphosphate ((NaPO3)6, 5 mg/100 ml) and stored >12 h in an overhead shaker. The fraction

quarry (Tokaj, Hungary). Stratigraphy and chronology from top to bottom (uncalibratedCharcoal layer (27.491 � 360 BP) e Upper palaeosol (32e26 ka BP) eMiddle loess layerk (Miocene pyroxene dacite). Due to logistic reasons the profile had to be split into two

A.-K. Schatz et al. / Quaternary International 240 (2011) 52e61 55

>63 mm was sieved off and weighed by hand. Measurementswere performed on a Malvern Mastersizer (Malvern Instruments,Worcestershire, UK) with a measurement range of 0.02e2 mmand a resolution of 0.25 F. Measurements were repeated once totest the reproducibility of the results, which was usually well above90%.

3.3. Magnetic Susceptibility

Sub-samples were ground, filled in 6 cm3 plastic boxes,compressed, and fixed with cotton wool. Low-field magneticsusceptibility was measured using a KLY-3 Kappa-Bridge (Agico,Brno, Czech Republic) with an AC field of 300 A m�1 at 875 Hz.Frequency dependent magnetic susceptibility was measured witha Magnon Susceptibility bridge (Magnon, Dassel, Germany) andAC fields of 300 A m�1 at 300 Hz and 3000 Hz, and expressed as

cfd ¼h�

clf � chf

�.clf

i*100 (1)

with 8fd: frequency dependent susceptibility [%],8lf: low-frequencysusceptibility [�],8hf: high-frequency susceptibility [�].

3.4. Alkanes

n-Alkane concentrations of the sediment samples weremeasured according to the Soxhlet extraction method of Zech andGlaser (2008). Lipids were extracted for 24 h with methanol/toluene (7:3) from sediment sub-samples of 150 g. Androstane(C19H32, 40 mg) was added as internal standard. After concentrationof the extract, co-eluted esters were saponified by heating theconcentrated extracts with sodium hydroxide (NaOH, 0.5 M) inmethanol (100 �C, 10 min). The hydrocarbon fraction was solvent-extracted twicewith 3ml hexane and purified on aluminium oxide/silica (5% deactivated) columns with hexane/toluene (85:15). n-hexatriacontane (C36H74, 40 mg) was added as recovery standard.For the quantification of the alkane fraction, an HP 6890 gas chro-matograph equipped with a flame ionisation detector (FID) wasused. The odd-over-even predominance (OEP) was calculated as

OEP ¼ ½ðC27 þ C29 þ C31 þ C33Þ=ðC26 þ C28 þ C30 þ C32Þ� (2)

Fig. 3. Schematic stratigraphy and overview of all proxies used in this study (from left to righsolid line), d15N (grey solid line), frequency dependent magnetic susceptibility (8fd, black solisolid line). Grey shaded areas indicate the position of (palaeo-) soils.

3.5. C and N stable isotopes, elemental concentrations

Elemental concentrations of C and N, as well as d13C and d15Nvalues, were measured after the removal of carbonates (10% HCl)and dry combustion of a 50 mg sub-sample using an NA 1108elemental analyser (CE Instruments, Milan, Italy) coupled toa continuous flow isotope ratio mass spectrometer via a ConflowIII interface (Finnigan MAT, Bremen, Germany). Acetanilide(C6H5NH(COCH3), Merck, Germany) was used as calibration stan-dard. The stable isotopic composition of a sample relative to aninternational standard (V-PDB, atmospheric N2) is expressed inper mil in the international delta notation according to equation (3)

d ¼h�

Rsample=Rstd�� 1

i*1000 ½&� (3)

where R is the ratio of the heavier to the lighter isotopes ofthe element (13C/12C, 15N/14N). Reproducibility of the isotopemeasurements based on the equipment described above is usually�0.2& or better (Gebauer and Schulze, 1991).

4. Results

4.1. Stratigraphy

In order to compare the results with those from previousstudies, a rough stratigraphy was established during fieldworkbased on sediment colour, density, soil aggregation, carbonatemycelia and fossil roots. It is largely corroborated by the analyticalparameters and is well in agreement with previous investigations(Sümegi and Hertelendi, 1998).

Magnetic and grain size data parallel lithological variationswithin the profile and reflect changes in past climatic and envi-ronmental conditions. Variations of the magnetic properties arerelated to soil forming processes and reflect differences incomposition, concentration and particle size of magnetic mineralsin the sediment (e.g. Evans and Heller, 2001). The relative amountof ultrafine magnetic grains near the SP/SD (superparamagnetic/single domain) threshold, which have predominantly beenformed during pedogenesis (Maher, 1998), is expressed as thefrequency dependent susceptibility 8fd. 8fd values of the Tokajprofile vary between 2.5 and 3.1% for loess layers and 4.0e7.5%for palaeosols (Fig. 3). Corresponding mass susceptibility values are

t): Relative contribution of trees and shrubs [%] based on corrected n-alkane data (blackd line), TOC (black dashed line), grain size fractions >30 mm (black solid line), d13C (grey

A.-K. Schatz et al. / Quaternary International 240 (2011) 52e6156

22e35 m3kg�1 � 10�8 for loess and 35e48 m3kg�1 � 10�8 forpalaeosols (not shown here).

Grain size distributions for all samples show a typical bimodaldistribution (not shown here) with a main peak around 55 mm(palaeosols: 40 mm) and a second peak in the clay fraction at0.35 mm. This pattern has already been reported in other loessstudies as well and indicates two distinct transport processes, i.e.short suspension transport for silt and long suspension transportfor clay-sized particles (McTainsh et al., 1997; Sun et al., 2002,2004). Furthermore, clay minerals are also formed by weatheringand pedogenetic processes. In order to depict changes in thegrain size distribution of deposited dust and palaeosols caused bychanging climatic energy levels and wind strength, the grain frac-tion >30 mm was used (Lu et al., 1999). According to Fig. 3, typicalpercentages of coarse grains in the middle loess layer are 45e55%and 55e65% in the upper loess layer, whereas percentages forpalaeosols are significantly lower and rarely exceed 40%.

In Fig. 3, the results of the grain size and MS measurementsare plotted versus depth. Palaeosols and loess layers can clearlybe distinguished based on these results, as palaeosols are clearlycorrelated with almost twice as high 8fd values as loess andconsiderably decreased coarse grain percentages. This is in agree-ment with the standard model of loess deposition under high-energy climatic levels, allowing coarser grains to be transported.Palaeosols, on the contrary, formed under low-energy conditionswhen fewer and finer grains were transported and deposited.At the same time, small magnetic minerals (<30 nm; maghemite(Fe3O4), magnetite (Fe2O3)) formed in situ during pedogenesis;they are the main source of the enhanced MS signal of palaeosols.Rather similar 8fd and grain size values for palaeosols suggestthat pedogenesis was equally intense for both soils, whereasdistinctly different coarse grain percentages for the loess layerssuggest that the deposition of the upper loess layer took placeunder rougher climatic conditions with stronger winds than duringthe formation of middle loess layer. Furthermore, climatic condi-tions and wind strength also varied within the deposition of onesingle stratigraphic unit, which is clearly visible from the saw-tooth pattern of the depth curve.

The modern topsoil is barely discernible from the 8fd and grainsize values. This is in agreement with visual field observations. Therecent topsoil is only weakly developed, which is probably due toerosion by sheet wash or connected to the mining activities.

Fig. 4. A) Alkane pattern of sediment sample A8 from the upper loess layer (2.00 m depth). Ta high amount of long-chain n-alkanes (C25 to C33) and a predominance of odd-numbered caralkane contribution from grasses and herbs. B) Depth function showing the uncorrected n-a(high values indicate less degradation). C31/C27 values >1 are commonly interpreted as domtree- and shrub-derived alkanes. In this figure, the highly significant correlation coefficientdegradation effects.

4.2. C and N elemental concentrations and stable isotopiccompositions

4.2.1. Total organic carbon (TOC)Observed total organic carbon (TOC; Fig. 3) is close to zero

for the entire profile, especially for loess layers, whereas (palaeo-)soil samples are characterised by a significant and systematicincrease in TOC (0.5e1.0%). This is caused most likely by increasedbiomass production during periods of soil formation and againconfirms the established stratigraphy. Slightly negative TOC valuesare caused by the calibration method in the Laboratory of IsotopeBiogeochemistry, BayCEER, which does not allow determiningreliable absolute TOC concentrations at very low concentrations.However, this does not limit the interpretation of systematic TOCtrends.

4.2.2. Stable carbon isotopesExcept for two outliers, the d13C depth function of the Tokaj

profile shows very little variation with values ranging approxi-mately from�24 to�25& (Fig. 3). These are typical values reportedin the literature for soils developed under plants using the C3

photosynthetic pathway (Ambrose and Sikes, 1991). C3 plantstypically dominate in temperate, arctic and alpine ecosystems.Almost all trees and cold steppe grasses belong to this group. (Sub-)tropical grasses, in contrast, follow the C4 photosynthetic pathway.They are adapted to higher temperatures and drier conditions andare more competitive at lower CO2 atmospheric partial pressure.The latter two climatic conditions may have favoured the expan-sion of C4 grasses in the Carpathian Basin. However, the carbonisotopic results exclude C4 vegetation, as these plants reveal verydifferent carbon isotopic values ranging from �8 to �16& (Parkand Epstein, 1961; Ambrose and Sikes, 1991). This suggests that,for the entire time span during which the profile accumulated, C3plants have been the main vegetation type. Smaller d13C variationsin loess-palaeosol sequences may furthermore reflect changes insoil organic matter (SOM) mineralisation (Zech et al., 2007).Such shifts are, however, not discernible in the transitions fromloess to palaeosols and vice versa.

4.2.3. Stable nitrogen isotopesApart from d13C, d15N is influenced by mineralisation processes

and especially by N losses, and may be a more sensitive proxy

he pattern resembles those of epicuticular plant leaf waxes which are characterised bybon atoms (odd-over-even predominance, OEP). The dominance of C31 suggests a majorlkane ratios C31/C27 (black) and the OEP (grey) as proxy for the amount of degradationinance of grasses and herbs, whereas C31/C27 values <1 suggest a high contribution of(r ¼ 0.965) of the two proxies suggests that the C31/C27 values are not independent of

A.-K. Schatz et al. / Quaternary International 240 (2011) 52e61 57

than d13C in order to reconstruct vegetation changes. Fig. 3 revealsthat d15N values show significant and systematic variations, withvalues ranging from þ0.5 to þ6&. Soil layers are characterised bymore positive d15N values compared to loess layers. This isotopicenrichment most likely reflects increased N losses due to enhancedSOM mineralisation during the formation of palaeosols. Palae-oclimatically, this can be attributed to higher temperatures. Onecould also speculate that changes of seasonality of precipitation andsoil water availability influenced SOM mineralisation. FollowingAmundson et al. (2003), Aranibar et al. (2004) and Handley et al.(1999), mean annual temperature (MAT) seems to be positivelycorrelated, and mean annual precipitation (MAP) negatively corre-lated with d15N. If applied to this data, phases of soil developmentcoincidewith an opening of the N cycle and 15N enrichment, causedby rising MAT and, possibly, decreasing MAP. Periods of loessaccumulation are linked to a rather closed N cycle, decreased d15Nvalues and hence lower temperatures and increased precipitation.

4.3. Alkanes

4.3.1. Uncorrected alkane dataTotal alkane concentrations in the samples range from 0.6

to17.4 mg/g sample. In both loess and palaeosol samples the long-chain n-alkanes (C25 to C33) dominate and reveal a pronouncedodd-over-even predominance (OEP; see Fig. 4A), which is charac-teristic of epicuticular plant leaf waxes (Kolattukudy, 1976). Whiletree and shrub alkane patters are usually dominated by the alkanesC27 and C29, and grasses and herbs by C31 and C33, in contrast,alkane ratios such as C31/C27 have often been used for palae-oenvironmental studies, enabling us to differentiate betweentree/shrub-dominated and grassland-dominated ecosystems. Afirst tentative depth plot of C31/C27 (Fig. 4B) shows generally ratherbalanced alkane ratios of 2e3, indicating a grassland-dominatedecosystem throughout the whole profile. Strikingly, relatively lowalkane ratios of around 2e3 characterise the upper and lowermostpart of the profile, whereas higher C31/C27 ratios of up to 10 occurbetween 8 and 14 m. It might be tempting to interpret these shiftsin terms of vegetation changes. However, this first interpretationmay not be valid, as recent publications have shown that plant leafwax alkane patterns are prone to systematic degradation effects insoils, resulting in lower OEP values and more balanced alkanepatterns (Zech et al., 2009a). Hence, the OEP has been proposed as

Fig. 5. Alkane ratio degradation correction after Zech et al., 2010. Typical patterns how alkadataset. The OEP is used as a degradation proxy and samples (black triangles) are compareddashed line, bottom). Percentage contributions of trees/shrubs can be calculated using a mixiespecially samples with lower OEP values plot slightly closer to the ‘forest degradation line’.but a contribution of tree-derived alkanes is possible as well.

a proxy for the degree of alkane degradation in soils (Buggle et al.,2010; Zech et al., 2009a, 2010). Fig. 4B shows that the OEP valuesof the Tokaj loess-palaeosol sequence vary strongly, with valuesranging from 5e20. This suggests that the degree of alkanedegradation is not uniform throughout the profile. Furthermore,Fig. 4B depicts that the depth functions of C31/C27 and the OEPare highly correlated (r ¼ 0.965), indicating that degradationeffects, and not vegetation changes, may be the main cause forvarying C31/C27 values. A more detailed alkane-based vegetationreconstruction depends on an adequate correction procedureaccounting for these degradation effects.

4.3.2. Correction procedureThe authors are currently aware of two published methods to

correct for the effects of degradation (Buggle et al., 2010; Zech et al.,2009a). Buggle et al. (2010) assess the degradation effect byconsidering the OEP and C31/C27 decrease in the upper decimetresat their specific study sites. Given the fact that the Holocene soil atthe study site is most likely eroded, and no OEP decrease in the firstdecimetres was observed, the end-member modelling approach ofZech et al. (2009a) was used. It is based on a large reference datasetof modern plant, soil and sediment samples originating from bothgrasslands and forests. Using the OEP as a degradation proxy,a simplified mathematical description of how alkane ratios changeduring degradation can be derived from this database (‘degradationlines’). Fig. 5 shows that all samples plot very closely to the‘grassland degradation line’. The same holds true for all otheralkane ratios (not depicted here) and confirms that grasslandecosystems always dominated. However, some samples, especiallythose with lower OEP values, seem to plot slightly but systemati-cally closer to the ‘forest degradation line’ (Fig. 5). Although thesevariations could be explained with inner- and interspecies vari-ability of the alkane patterns (Zech et al., 2009a), a contribution oftree-derived alkanes cannot be excluded. Therefore, the percentagecontribution of tree/shrub-derived and grassland-derived alkaneswas calculated according to the procedure described by Zech et al.(2009a) using their end-member equation model. In order toensure the robustness of this approach, four common alkaneratios (C31/(C31 þ C27), C33/(C33 þ C27), C31/(C31 þ C29) and(C31 þ C33)/(C31 þ C33 þ C27 þ C29)) were corrected using thismethod and the average of these four ratios is calculated (Fig. 6).For details, the reader is referred to the literature.

ne ratios change during degradation (‘degradation lines’) are derived from a referenceto the degradation lines of grasses/herbs (grey solid line, top) and trees/shrubs (grey

ng equation. All Tokaj samples plot closely to the ‘grassland degradation line’. However,This could be explained with inner- and interspecies variability of the alkane patterns,

Fig. 6. Modelling results of the four most relevant alkane ratios depicted as the percentage contribution of tree- and shrub-derived alkanes. Please note that negative values do notimply that the model is incorrect, but rather reflect the model-inherent error due to scattering of the alkane ratios in the reference database. The plot to the very right illustrates theaverage contribution of trees and shrubs calculated as the mean of the four ratios.

A.-K. Schatz et al. / Quaternary International 240 (2011) 52e6158

4.3.3. Corrected alkane resultsThe modelling results, i.e. percentage estimates for tree/shrub-

derived alkanes, of the 4 alkane ratios are illustrated in Fig. 6. Notethat negative values do not imply that the model is incorrect, butreflect the model-inherent error due to scattering of the alkaneratios in the reference database. After averaging over the fourmodelling results the uppermost samples show 27e36% tree/shrubvegetation. This agrees very well with the recent vegetationdistribution on top of the profile, which is grass-dominated, butsingle trees and a considerable amount of shrubs are present aswell. Strikingly, the depth functions of all four modelling resultsreveal similar trends, suggesting that (i) trees/shrubs may havecontributed to the vegetation varyingly and repeatedly duringthe formation of the upper loess layer, (ii) the upper palaeosoldeveloped under pure grassland, and (iii) small amounts of treesand shrubs may have been present during the formation of thelowermost loess layer.

5. Discussion

5.1. Palaeosols

Compared to the loess layers, the two palaeosols revealsystematic differences in the results obtained from the laboratoryanalyses (e.g. TOC, MS, grain size distribution), which allowsdrawing palaeoclimatic conclusions. Both palaeosols show elevatedbiomass accumulation, indicated by increased TOC. At the sametime, tree and shrub percentages decrease significantly. Thissuggests that trees and shrubs did not contribute to biomassaccumulation, which must therefore be entirely attributed toa productive grass-steppe environment. Both palaeosols coincidewith increased d15N values, pointing at increased N losses due toaccelerated mineralisation. Following the N-cycling modeldescribed in section 4.2 and its relations with climate, the elevatedmineralisation rate was most likely caused by a shift towards drierand warmer climatic conditions, as typically found in regionswith pronounced climatic seasonality. Seasonal climates, as e.g.the modern Mediterranean climate, are characterised by humid,cool winters and hot, dry summer seasons due to the varyinginfluence of mid-latitude pressure systems.

However, although summers were too dry to allow for trees togrow, enhanced biomass production and pedogenesis lead tothe formation of two palaeosols, which are clearly discernible in the

field and in the analytical data. Climatic seasonality might help toexplain this apparent contradiction of inhibited tree growth andpedogenesis at the same time. Reduced precipitation and increasedevapotranspiration in summer inhibited tree growth indeed, butwith the majority of precipitation confined to the cooler months,conditions were in favour of grass and herb species, enabling themto thrive and form extensive, productive grasslands.

In order to further test and to validate or reject these interpre-tations, the data were compared to the results of previous palae-oenvironmental studies conducted at Tokaj. Sümegi and Rudner(2001) and Sümegi and Hertelendi (1998) analysed molluscsfound in the upper palaeosol at several different locations aroundKopasz Hill, Tokaj. They propose milder and wetter climaticconditions, leading to closer vegetation cover, reforestation andpedogenesis, as the number of thermo-, hygrophilous and wood-land-dwelling species increases. However, there is also a significantamount of open land-dwelling and xerotolerant species, leadingthem to conclude that very distinct microclimatic conditions pre-vailed on the northern and southern slopes of the hill, so that botharid steppe and humid woodland taxa could exist close to eachother (‘mosaic-like environment’). From these relic spots on thenorthern slopes, refugial flora and fauna could have spread quicklyas soon as climatic conditions improved. Reviewing the molluscandistribution of the Patkó quarry profile only (Sümegi and Rudner,2001), there are considerable amounts of both hygro- andxerophilous, as well as open land-dwelling molluscan species.This might support the interpretation of pedogenesis underextensive grass steppe environments on the eastern side of the hill,where a warm, but rather dry microclimate might have evolvedcompared to the northern side.

5.2. Treeless-steppe intervals

Two layers with a striking decrease of tree/shrub percentages(3.5 m) or extremely low values (5 m; see Fig. 3) can be found.However, pronounced climatic seasonality similar to the conditionsthat prevailed during palaeosol formation can be excluded asexplanation, as grain size, 8fd and d15N data indicate differentclimatic conditions. The contribution of the coarse grain fractionis significantly elevated, pointing at a high-energy climate withstrong winds and loess deposition. d15N values are relatively low,suggesting a closed N cycle with low N mineralisation. Accordingto the N-cycling model and its relations with climate, this low

A.-K. Schatz et al. / Quaternary International 240 (2011) 52e61 59

mineralisation rate could have been caused by a shift towardscooler and more humid periods characterised by a lower MAT and,possibly, higher MAP e conditions that would not necessarilyinhibit tree growth but, on the contrary, rather provide a favourableenvironment for tree and shrub growth. At present, there is noevidence in the proxy data to explain this sudden, temporarydecrease of the tree population.

However, cycles of retreating tree vegetation have also beenproposed by Rudner and Sümegi (2001) based on malacologicalanalyses carried out at Tokaj and at various other locations in theCarpathian Basin. They report two periods of cooler, drier climateduring which more xero- and mesophilous, cryophilous and openland-preferring species occur and date them to 25e23 ka BP and20e18 ka BP; the latter probably coincides with the LGM. Thesecool and dry periods leading to what the authors describe as “coldcontinental (loess) steppe” may correspond to the treeless-steppeperiods, and both are situated in similar stratigraphic positions inthe profiles. Detailed ages are required to ultimately correlate theseperiods.

5.3. Periods of tree-steppe or ‘open parkland’ environments

In the alkane depth function of the alkane modelling resultsthere are 5 peaks indicating an increase in the relative amount oftree/shrub vegetation cover (Fig. 3). Four occur in the upper loesslayer (0e1 m, 1.75e3 m, 3.75e4 m, 5.25e6 m), and one below thelower palaeosol (15.5- bottom). Grain size distribution for thesame time intervals shows clearly that rather coarse grain fractionsprevail, and 8fd is low, thus periods of milder climate and soilformation can be excluded as an explanation for the expansion oftrees. On the contrary, grain size data rather suggest high-energyclimatic conditions with strong winds and possibly high dustaccumulation rates. However, these periods coincide with lowerd15N values, indicating that a cooler, more humid climate evolvedthat favoured tree and shrub growth. This is most likely caused bya shift from the pronounced seasonal climate to more balancedclimatic conditions where the majority of precipitation is not onlyconfined to thewinter months, but evenly distributed over the year,or shifted towards the summer months, similar to the modernclimate at Tokaj. The uppermost tree peak sample (0e1m) providesevidence for this view, as it was taken from the recent soil andsome tenths of centimetres of material below, thus representingmodern Holocene climate and vegetation.

The alkane peaks at 3.75e4 m and 1.75e3 m might be linkedto two ‘microinterstadials’ described by Sümegi and Rudner (2001)and dated to 23e20 ka BP and 18e16 ka BP. These short phasesof warmer, wetter climate are characterised by an increase in theamount of intermediate and woodland-dwelling molluscs pointingat the development of a forest-steppe environment with signifi-cantly more trees than in the preceding periods. For trees andshrubs to spread quickly during these short-term climatic oscilla-tions, it is highly likely that a refugial spot existed, e.g. on thenorthern slopes of the hill, from where flora and fauna couldadvance as soon as climatic conditions improved. The shift tomore favourable climate, more precisely more humid conditions,is largely confirmed by low d15N values, which also coincide withthe lowest alkane peak (15.5 m e bottom). However, for this periodthe malacology-based interpretations and the study data differslightly, as Sümegi and Hertelendi (1998) report abundant cryo-,hydrophilous and open habitat-preferring species and concludethat the landscape must have been grass steppe- or tundra-like,whereas the alkane results suggest denser tree and shrub vegeta-tion cover, similar to that of today.

The alkane peak at 5.25e6 m, directly above the upper palae-osol, may correspond to a stratigraphic unit described by Sümegi

and Rudner (2001) for all of the palaeosoleloess profiles aroundKopasz Hill. This characteristic ‘charcoal layer’, consisting of burntPicea (spruce) pieces, has been dated to 28e26 ka BP and inter-preted as the result of extensive natural wildfires occurringafter pedogenesis ceased. Further evidence for Picea woodlandcomes from fossilized wood branches and trunks of the sameage that have been found at other outcrops on Kopasz Hill (Sümegiand Rudner, 2001). Although the alkane biomarker results do notsupport Sümegi and Rudner’s interpretation of extensive woodlandduring the time of soil formation, the data do confirm that directlyafterwards trees and shrubs spread again and wildfires mighthave occurred, preserving some of the evidence as charcoal inthis specific stratigraphic position. In this interpretation, d15Ndata suggest cooling after pedogenesis ceased, stimulating theexpansion of trees and shrubs.

6. Conclusions

This multidisciplinary study of the loess-palaeosol sequenceat Tokaj, NE Hungary, reveals a very detailed Late Pleistocenerecord. The results, in combination with previous findings, mayserve to establish this site as an important record of palaeoclimateand palaeoenvironment in the Carpathian Basin.

During the whole time span the profile covers (ca. 70e12 ka BP),cyclic climatic and environmental changes occurred. The datasuggest two cool, treeless-steppe periods between 26 and12 ka BP, which possibly also include the LGM, but also intervals inwhich trees and shrubs expanded. Based on alkane and stable Nisotopic data, pedogenesis occurred under fertile steppe-grass-lands, probably in an intensified, warm seasonal climate.

The results emphasise the importance of deepening the under-standing of the mechanisms of Pleistocene climate change and itsimpact on the environment. This would constitute a major steptowards a more detailed spatial and temporal reconstruction ofQuaternary environmental and climate dynamics. In this study,a combination of plant-derived biomarkers and stable C andN isotopes has been applied for thefirst time in the Carpathian Basinand provides detailed, new results that increase the knowledgegained from previous studies. Combined complementary biogeo-chemical proxies, as used in this study, seem to be a promising toolfor forthcoming investigations on loess-palaeosol sequences.

Acknowledgements

The authors would like to thank G. D. Páll and G. Persaits(University of Szeged) for help during fieldwork, Prof G. Gebauer andhis team (Biogeochemistry Group, BayCEER, University of Bayreuth)for stable isotope and elemental concentration measurements, A.Mergner (University of Bayreuth) for support in the laboratory and K.Schmidt (University of Tübingen) for help with graphs and figures.We also appreciated the comments of the editor and the anonymousreviewer. A. Schatz received financial support from the GeographicalInstitute, University of Tübingen. M. Zech greatly acknowledges thesupport provided by the Alexander von Humboldt-Foundation.

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