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International audience; We present the first high-resolution Holocene pollen, plant-macrofossil, and charcoal records from the upper-montane zone in the central Dinaric Alps. Drawing on these new records from well-dated lacustrine sediments of Zminje Jezero (ca. 1500 m a.s.l.; Montenegro) and on independent chironomid-inferred summer temperatures, we explore long-term ecosystem responses to variations in climate, fire disturbances and land use, as well as legacy effects of past environmental changes. A mixed spruce-fir forest established in the upper-montane zone around 9500 cal BP, and Fagus sylvatica became co-dominant with the two conifers after 5000 cal BP. Prehistoric land-use pressure was overall remarkably low, but increased since 2000 cal BP and was highest after the Middle Ages. We found a significant positive relationship between biomass burning and summer temperature, indicating that fires were mostly climate driven. Picea abies was insensitive to summer temperature, biomass burning and human impact, which supports the view that spruce forests may not be significantly impacted by fire. In contrast, Abies alba and other disturbance-sensitive trees ( Tilia, Ulmus, Fraxinus excelsior-type) show significant negative responses to land-use pressure and positive responses to summer temperature. This supports the notion that these species may be well-adapted to warmer-than present summer temperatures and that their populations declined in recent millennia due to land-use activities. Conversely, F. sylvatica was sensitive to summer temperatures but was promoted by low biomass burning, indicating that its expansion in the spruce-fir dominated forest was enhanced by the onset of cooler and possibly also moister climatic conditions as well as by fire disturbances.

We measured stable isotopes (δ18O and δ13C) in Sphagnum cellulose that was extracted from a long peat core drilled in the ombrotrophic Mohos peat bog, Ciomadul Mountain, Romania. The 10-m-long peat profile spans the period from 11,800 cal yr BP to present. The δ18O and δ13C data indicate there were several cooling events and warm periods in the area of the Mohos peat bog during the Holocene. The 8.2-ka cold event, however, was not detected using δ18O and δ13C values. Response of the peat bog to changing environmental conditions was inferred using data on organic matter accumulation, independent of the stable isotope results. All cool periods during the Holocene, whether of short or long duration, were identified as times of reduced organic matter accumulation rate. Similarly, dry periods were also correlated with reduced accumulation rates of organic matter.

Over the last 10 years several alpine lakes were studied from the Southern Carpathian Mountains (SCM) using paleoecological, geochemical and stable isotope techniques. The aim of these studies were to obtain quantitative climate reconstructions for the alpine region for the Late Glacial (LG) and Holocene, reconstruct tree and timberline changes and examine how rapid climate change events manifested in this region, what are the regions characteristics. Absolute chronologies were also supported here for the first time with tephra chronology in the Early Holocene. In addition, environmental DNA studies were used to explore what molecular techniques can add to a more exact and often species level reconstruction of past floristic compositions. This talk will summarize these researches and use multivariate statistics to examine leads and lags in ecosystem response at multiple sites (Retezat, Pareng, Fogaras, Ciomadul Mts). These analyses first of all demonstrate that the amplitude of warming was attenuated in the SCM at the GS-2/GI-1 transition relative to NW Europe (~2,8-3 oC), summer temperatures increased abruptly already at 16.2 ka cal BP in direct response to the weakening polar circulation and the tripartite GS-1 had weak summer temperature decrease (oC), but winter cooling was strong. Regarding the order of ecosystem changes, lead and lag analysis revealed

A coupled accelerator mass spectrometer–gas interface system has been successfully operating at the Hertelendi Laboratory of Environmental Studies, Debrecen, Hungary, since 2013. Over the last 6 years more than 500 gas targets were measured below 100 µg carbon content for carbon isotopic composition. The system was tested with blanks, OxII, IAEA-C1, IAEA-C2, and IAEA-C7 standards. The performance of our instrumentation shows good agreement with other published gas-interface system data and also shows a quite good agreement with the nominal value of international standard samples. There is a measurable but quite small memory effect after modern samples, but this does not significantly affect the final results. Typical ion currents at the low energy side were between 10–15 µA with a 5% CO2 in He mixing ratio. The relative errors average ±6% for samples greater than or equal to 10 µgC sample with mean count rates of 300 counts per microgram C for OxII. The blank is comparable with other systems, which is 0.0050 ± 0.0018 F14C or 34,000–47,000 yr BP, which allows for the routine measurement of both of small environmental and archeological samples.

Reconstruction of a floodplain area over the last 40.000 years (Tisza, Hungary) – comparative case study of 14C and OSL methods Titanilla Gréta Kertész 1 * , Buró Botond 1 , Hubay Katalin 1 , Sipos György 2 , Molnár Mihály 11Isotope Climatology and Environmental Research Centre, Institute for Nuclear Research H-4026, Bem tér 18/c, Debrecen, Hungary2Szegedi University, Department of Physical Geography and Geoinformatics H-6722, Egyetem str. 2-6, Szeged, Hungary*Correspondence to: Titanilla Gréta Kertész; e-mail: kertesz.titanilla@atomki.mta.hu Keywords: Tisza, Jászság-basin, radiocarbon AMS dating, OSL Abstract14C and OSL results of the 5 parallel, neighbouring cores (avg. depth 19 to 20 meters) were compared for a flood basin area (Jászság-basin). Four major sedimentary horizons were identified: meadow soil on the top; silty clay as the second horizon; a clay-silt section; and fine sand. 14C and OSL data were integrated into a consolidated age model by BACON software package. Formation of the recent top meadow soil (the upper 1-1.5m) falls in the Holocene. The mean conventional apparent radiocarbon age (940 ± 420 years) was used for correction of the radiocarbon reservoir effect of soil bulk ages. The SubAtlantic + SubBoreal section show increasing apparent deposition rates (~11 cm / ka). The silty-clay strata represents the whole Würm (Weichselian) Last Glacial to Upper Pleniglacial period (aDR ~6.3 cm/ka). The Ságvár-Lascaux interstadial climate period section was apparently much slower (aDR decreases from ~4.2 to ~1.6 cm / ka). About 10 to 60 cms of sediment must be missing from this section. The next part of the section is a very long period (~10 kyrs) with a stable, much greater aDR than even at the end of the Holocene (~20-25 cm/ky). The clayey silt layers fall into the Late Pleistocene / Middle Pleniglacial period, a period of nearly 7.000 years of sedimentation resulting in deposits with a thickness of ~9 m, shown a very high apparent deposition rate (aDR) about ~0.12 m/ka.The research was supported by the European Union and the State of Hungary, co-financed by the European Regional Development Fund in the project of GINOP-2.3.2-15-2016-00009 ‘ICER’.

This study applied bulk sediment geochemistry to reconstruct lateglacial and early Holocene climatic changes in a glacial lakes (Lake Brazi, 1740 m a.s.l. and Lake Lia, 1910 m a.s.l.) in the Retezat Mts. (South Carpathians, Romania). We studied how the changes of chemical element concentration in the sediment can indicate environmental changes, climate variations and human effects. Our aim was to develop analytical methods, which may complement the methodology of routinely applied paleoenvironmental methods and can be used to identify environmental changes in the past and help us reconstruct local and regional processes. In the Retezat Mts., Southern Carpathians, more than hundred glacial lakes were formed after the last glaciation. These glacial lakes are paleoecologically significant because they are characterized by continuous sedimentation since their origin to the present. In 2007 and 2008 continuous undisturbed sediment cores were obtained from Lake Brazi and Lake Lia in the Retezat Mts. (Southern Carpathians, Romania) with Livingstone and modified Kullenberg corers. The lowermost part of the sediment cores, covering the period between 9900 and 15 800 cal yr BP, was used for high resolution bulk analysis of major elements (Al2O3, SiO2, TiO2, CaO, MgO, K2O, Na2O, Fe2O3 and MnO). Linear discriminant analysis (LDA) was used to compare a priori classified main chemical groups. Subsamples from the core were priory ordered to “warm” and “cold” groups respectively, according to their age and evidence of cold and warm events in the record, as suggested by proxy correlation with the lateglacial event stratigraphy of North Greenland Ice Core Project (NGRIP). The discriminant function was calculated using concentration of major elements after log ratio transformation. Loss-on-ignition and silicon concentration were not used for the discriminant analysis, but regarded as comparison proxies for checking up the validity of outputs. The calculated discriminant values are good indicators of changes in sediment caused by climate change, as their values give the cold and warm directions. The “a posteriori” groups can be used to determine the period during which local changes differed from the climate changes in the North Atlantic region. The chemical composition of sediments deposited during the “cold” and “warm” periods shows differences in both sediments. The discriminant scores showed strong correlation with the NGRIP d18O data and with the pollen percentage sum of trees and shrubs. Discriminant analyses of bulk sediment major oxide chemical data may be a useful tool to identify the impact of climate events upon the nature and composition of materials delivered to a lake basin.Key words: climate reconstruction, sediment geochemistry, Retezat Mts.

A coupled accelerator mass spectrometer - gas interface system successfully has been operating at the Hertelendi Laboratory of Environmental Studies, Debrecen, Hungary since 2013. Over the last 6 years more than 500 gas targets were measured below 100 µg carbon content for carbon isotopic composition. The system was tested with blanks, OxII, IAEA-C1, IAEA-C2 and IAEA-C7 standards. The performance of our instrumentation shows good agreement with other published gas-interface system data and also shows a quite good agreement with the nominal value of international standard samples. There is a measurable but quite small memory effect after modern samples, but this does not significantly affect the final results. Typical ion currents at the low energy side were between 10-15 µA with a 5% CO2 in He mixing ratio. The relative errors average ±6% for samples greater than or equal to 10 µgC sample with mean count rates of 300 counts per microgram C for OxII. The blank is comparable with other systems, which is 0.0050 ± 0.0018 F14C or 34000-47000 yr BP, which allows for the routine measurement of both of small environmental and archeological samples.The research was supported by the European Union and the State of Hungary, co-financed by the European Regional Development Fund in the project of GINOP-2.3.2-15-2016- 00009 “ICER”. This work was carried out in the frame of the János Bolyai Research Scholarship (Mihály Molnár) of the Hungarian Academy of Sciences

This work focuses on building a high-resolution age-depth model for quantitative palaeoclimate study from the Mohos peat bog, East Carpathian mountains. The investigated core presents a continuous peat profile for the last 12 kyr. The chronology was based on 36 accelerator mass spectrometry radiocarbon (AMS14C) analyses of the separatedSphagnumsamples from different depths of the profile. DrySphagnumsamples for AMS dating were prepared using the classic acid-base-acid (ABA) method followed with an oxidative bleaching step to get clean cellulose.Sphagnumcellulose samples were measured by AMS using the EnvironMICADAS at the ICER (Debrecen, Hungary). A high-resolution chronology was obtained with the use of Bayesian age-depth modeling. Peat accumulation rate has been calculated and the sections with variable accumulation rate values were observed along the profile.

A comparative study was undertaken to adopt and evaluate a radiocarbon (14C) preparation procedure for accelerator mass spectrometry (AMS) measurements of cremated bones at our laboratory, including different types of archaeological samples (cremated bone, bone, charcoal, charred grain). All 14C analyses were performed using the EnvironMICADAS AMS instrument at the Hertelendi Laboratory of Environmental Studies (HEKAL) and the ancillary analyses were also performed at the Institute for Nuclear Research (ATOMKI). After the physical and chemical cleaning of cremated bones, CO2 was extracted by acid hydrolysis followed by sealed-tube graphitization and 14C measurement. The supplementary δ13C measurements were also performed on CO2 gas while FTIR was measured on the powder fraction. Based on the FTIR and 14C analyses, our chemical pretreatment protocol was successful in removing contamination from the samples. Good reproducibility was obtained for the 0.2–0.3 mm fraction of blind-tested cremated samples and a maximum age difference of only 150 yr was found for the remaining case studies. This confirms the reliability of our procedure for 14C dating of cremated bones. However, in one case study, the age difference of 300 yr between two cremated fragments originating from the same urn shows that other processes affecting the cremated samples in the post-burial environment can substantially influence the 14C age, so caution must be exercised.

This study summarizes the results of radiocarbon dating and age-depth modelling in four mountain lakes (Brazi, Gales, Bucura and Lia) in the Retezat Mountains. Altogether 69 AMS 14 C measurements were performed on these deposits, mostly on terrestrial plant macrofossils. In several cases, plant macrofossils, aquatic animal remains (Cladoceran eggs) and bulk sediment were measured from the same depth allowing for the comparison of various sediment components in terms of their dating potential. Age-depth models were developed using both Bayesian modelling with the BACON and smooth spline curve fitting with the CLAM software. In this study Bayesian models are applied to identify outlier 14 C dates, while smooth spline models are used to model sediment accumulation age-depth relations, as these are more likely to follow natural deposition time changes of lake sediments. Changes in sediment deposition times (DT) in relation to catchment size and climate are also studied. DT varied considerably in the late glacial (LG) part of the records. The sediment sequence characterised by high deposition rates during the late glacial (DT maximum around 100–110 years cm −1 ) was defined by small catchment size (Lake Brazi, 6 ha; surface area: 0.5 ha). In contrast, much slower LG sediment deposition in the southern slope lake characterised by large catchment area (Lake Lia, 171 ha, 20 years cm −1 ), principally reflecting strong erosion in these catchment areas at times when vegetation cover was scarce. Holocene was characterised again by variable DT values, but only Lake Gales showed extreme values: 62–110 years between 10,900 and 6050 cal yr BP, followed by much slower sediment deposition in the last 6000 years (av. 29 years cm −1 ). Generally, sediment deposition times were largely dependent on the stability and vegetation cover of the slope in the case of high altitude deep lakes, while lower altitude, shallow lakes showed slower sediment deposition time in the early and mid-Holocene, when summer insolation was higher than today. This reflects that in these shallow lakes in-lake organic production probably increased with summer insolation, which was a significant driver in the rate of deposition.

Sediment cores obtained from two deep (>15 m) glacial lakes were analyzed in context of terrestrial vegetation development and in-lake processes from the Retezat Mountains (Southern Carpathians, Romania). Only the Holocene parts were chosen for study for testing what is the connection between geochemical changes and biotas around and in the lakes. The lakes are situated at slightly different altitudes on the northern (Lake Gales, 1990 m a.s.l.) and southern slope (Lake Bucura, 2040 m a.s.l.), respectively. Changes in geochemical composition were relatively low amplitude during the studied period (10,300–1790 and 10,300–695 cal yr BP) in both lakes, but the applicability of enrichment factor (EF) for geochemical elements and diatom ecological traits (guilds) in paleoecological reconstruction were demonstrated in this paper. The main changes have been observed at ca. 10,670–9000, 6500 and 3100 cal yr BP in geochemistry, vegetation and siliceous algal assemblages. Catchment soil stabilization was apparent from ∼9000 cal yr BP onwards, in-lake and terrestrial productivity was the highest between 9000 and 6500 cal yr BP and human impact became the dominant driver in both terrestrial vegetation and sediment geochemical changes and in-lake processes over the last ∼3400 years in both lakes. The geochemical record displayed frequent erosional events within the Holocene. The strongest soil erosions clustered around 6500–7400 and 3200-900 cal yr BP.

International audience; We present the reconstruction of mire vegetation changes and fire history recorded in a continuous sediment profile that spans the last 20,000 cal yr BP from the Late Pleniglacial to Holocene in North-eastern Hungary. We also aimed to reveal past climate changes by using ecological requirements of specific aquatic plants as summer temperature indicators. Our results suggest the formation of a mesotrophic mire around 20,000 cal yr BP with brown moss, Betula sp. and Selaginella selaginoides cover beside the occurrence of Phragmites australis, Typha latifolia and T. angustifolia suggesting base-rich fen and tundra-like wet-ground habitats on the lakeshore. This community shifted to reed dominated swamp at c. 18,300 cal yr BP with inferred min. July temperatures of 12–15.7°C. Pinus sp., Betula nana, B. pendula/pubescens, Hippuris vulgaris and P. australis dominated until 16,600 cal yr BP pointing to shallow muddy stagnant water and colder climatic conditions than in the preceding interval. The most warmth-demanding species, T. latifolia and T. angustifolia indicated July mean temperatures > 14-15.7°C soon after the LGM. The formation of biogenic carbonate also started at an early stage; major accumulation occurred between 15,200 and 10,000 cal yr BP. In the Early Holocene, environmental indicator species (e.g. Phragmites australis and T. latifolia) pointed to warmer and shallower conditions, while the late Holocene was characterised by strong eutrophication and reed swamp dominance on the lakeshore. Elevated macrocharcoal concentration, wood fragments and remains of Typha species suggested frequent local fires and dry mire surface conditions during the last 1700 years.

Reconstructions of dust flux have been used to produce valuable global records of changes in atmospheric circulation and aridity. These studies have highlighted the importance of atmospheric dust in marine and terrestrial biogeochemistry and nutrient cycling. By investigating a 10 800-year-long paleoclimate archive from the Eastern Carpathians (Romania) we present the first peat record of changing dust deposition over the Holocene for the Carpathian–Balkan region. Using qualitative (X-ray fluorescence (XRF) core scanning) and quantitative inductively coupled plasma optical emission spectrometer(ICP-OES) measurements of lithogenic (K, Si, Ti) elements, we identify 10 periods of major dust deposition between 9500–9200, 8400–8100, 7720–7250, 6350–5950, 5450–5050, 4130–3770, 3450–2850, 2000–1450, 800–620, and 60 cal yr BP to present. In addition, we used testate amoeba assemblages preserved within the peat to infer local palaeohydroclimatic conditions. Our record highlights several discrepancies between eastern and western European dust depositional records and the impact of highly complex hydrological regimes in the Carpathian region. Since 6100 cal yr BP, we find that the geochemical indicators of dust flux have become uncoupled from the local hydrology. This coincides with the appearance of millennial-scale cycles in the dust input and changes in geochemical composition of dust. We suggest that this is indicative of a shift in dust provenance from local–regional (likely loess-related) to distal (Saharan) sources, which coincide with the end of the African Humid Period and the onset of Saharan desertification.

To investigate treeline and timberline dynamics in the Retezat Mountains (Romanian Carpathians), late glacial and Holocene sediment sequences from four lakes were studied. The south and north slopes of the mountain range were compared using two lakes from the north flank (Lake Brazi, 1740 m a.s.l. and Lake Gales, 1990 m a.s.l) and two from the south flank (Lake Lia, 1910 m a.s.l. and Lake Bucura, 2040 m a.s.l.). Macrofossil and stomata analyses were performed to assess changes in the local vegetation, supplemented by pollen, charcoal and loss-on-ignition analyses. Our results show that treeline reached Lake Brazi on the northern side during the late glacial (ca. 14,000 cal yr BP) and then Lake Gales between 11,000 and 10,800 cal yr BP. During the early Holocene the upper limit of closed forest, the timberline, reached and passed Lake Brazi and has stayed above it since, but it has never reached Lake Gales at 1990 m a.s.l. The expansion of Larix decidua in the late glacialand early Holocene around Lake Brazi is unique. Stomata and macrofossils of Abies alba are also more abundant in the northern records. On the southern flank, treeline reached Lake Lia at around 12,000 cal yr BP, and was either very close to or at the elevation of Lake Bucura between ca. 8600 and 3000 cal yr BP. Timberline reached Lake Lia at ca. 8000 cal yr BP, some 3000 years after Lake Brazi, only 170 m lower on the north slope. Local fire events delayed the advance of timberline around Lake Lia in the early Holocene in a dry continental climate. The surrounding forest was dominated by Picea abies with individuals of Pinus cembra and stands of P. mugo until about 3000 cal yr BP when timberline retreated below the lake. Maximum elevation of timberline was attained between ca. 8000 and 3000 cal yr BP, after which it descended in response to climate cooling. Regional climate change appears to be the main driver of treeline dynamics, but it was modified by local climatic differences due to slope aspect. The first signs of human disturbance appeared ca. 4200 cal yr BP, when naturally open areas were used as alpine pastures. Human impact in the treeline ecotone, mainly burning and grazing, was intensified after ca. 2600 cal yr BP, contributing to the widening of the ecotone and the lowering of the timberline.

Remains of aquatic biota preserved in mountain lake sediments provide an excellent tool to study lake ecosystem responses to past climate change. In the PROLONG project a multi-proxy study was performed on sediments of glacier-formed lakes from the Retezat Mountains, Southern Carpathians (Romania). The studied lakes (Lake Brazi and Gales) are situated on the northern slope of the mountain at different altitudes (1740 m and 1990 m a.s.l.). Our main objectives were 1) to describe the main limnological changes in these lakes during the last ca. 15,000 years and 2) to summarize the environmental history of the studied lakes based on taxonomical and functional patterns of the biological proxies. For this synthesis we used the results of diatom and chironomid analyses, and indirect biotic and abiotic parameters, including sediment organic matter (LOI) content, geochemical element concentrations (Al, Ca, S, Sr) and biogenic silica content. Using multivariate numerical approaches we analysed changes in the assemblage structure of siliceous algae and chironomids, compared temporal patterns among proxies, examined the relationship between potential driving factors, chironomid and diatom assemblage changes and identified paleolimnological phases of the lake successions. Changes in assemblage composition and aquatic ecosystem state apparently followed summer insolation, local climatic conditions and local productivity changes driven by these. Diatom and chironomid assemblages generally changed in a similar direction and at a similar time within a lake, but differed to some extent between Lake Brazi and Gales. At both lakes the strongest variations were observed in the Late Glacial and the first half of the Holocene. The strongest Holocene assemblage changes took place in the earliest Holocene in Lake Brazi, but extended into the mid-Holocene in Lake Gales, following long-term insolation changes and climatic changes. In addition, three common zone boundaries were identified: at ca. 14,200 and at ca. 6500 cal yr BP for every records and at ca. 3100 cal yr BP for diatom records in both of the lakes and for the chironomid record of Lake Brazi. This multi-proxy synthesis provides comprehensive data that increase our understanding of the past variability of lake ecosystem functioning and biodiversity in East-Central Europe.

The Middle to Upper Palaeolithic transition is one of the crucial periods of change in the prehistory of Europe due to the full emergence, continent-wide, of modern human lithic technologies, and detrimental of Neanderthal survival. Knowledge about the transition is growing, however, the evidence for cultural and technological developments for the Middle Palaeolithic in the Carpathian – Lower Danube Basin is still rather sparse. Here we discuss latest findings arising from a chronological investigation of Middle Palaeolithic assemblages within the Varghis karst, Eastern Transylvania, Romania. Combining our first chronological results with information from previous excavations, we can distinguish two main stages of habitation (albeit Middle Palaeolithic lithics and faunal remains appear scattered throughout the investigated profile) within the Abri 122 rock shelter. In order to augment the typological cultural considerations, we applied direct radiocarbon dating on bones and charcoal from within the occupation layers. Radiocarbon dating of bones suggests that the Middle Palaeolithic sequence is older than the upper dating limit of the method, whereas direct luminescence ages on the lowermost productive horizon and immediately above it indicate surprisingly old ages of ca. 106–141 ka (OSL – optically stimulated) or 99–174 ka (IRSL – infrared stimulated). Multiple-protocol dating of charcoal found within the two habitation layers produced ages >38 14 C ka BP, also suggesting that the lowermost lithic-rich horizon pertains to the Middle Palaeolithic industries. Overall, the recovered lithics, currently forming one of the most significant collections for Romania, are fully consistent with two main habitation phases connected to Middle Palaeolithic cultural affinities. The occurrence of a volcanic ash layer within Ursului Cave and originating from the Ciomadul volcanic complex (Carpathians) is first reported here. Recently dated to ∼ ≥ 43 (−50) ka, it might represent an important marker horizon, providing that it is identified within other Palaeolithic cave assemblages.

Two high-altitude lake-sediment sequences (Lake Lia, 1910 m a.s.l. and Lake Bucura, 2040 m a.s.l.) from the Retezat Mountains (South Carpathians, Romania) were analysed using multi-proxy methods to study responses of treeline, timberline and alpine/subalpine vegetation to climate change and human impact during the past 16,000 years. Woody species ( Pinus mugo, Pinus cembra, Picea abies and Juniperus communis) reached Lake Lia between 12,000 and 11,800 cal. yr BP, whereas P. mugo colonised the shores of Lake Bucura at 9600 cal. yr BP. Lake Lia was in the timberline ecotone between 8000 and 3200 cal. yr BP, in semi-open P. cembra and Picea abies woodland, probably mixed with P. mugo on the steeper slopes. Lake Bucura was surrounded by the upper part of the krummholz zone during the mid-Holocene. The increase in P. cembra after c. 6000 cal. yr BP around Lake Lia suggests that the composition of the timberline forest changed. The disappearance of P. cembra and Picea abies around Lake Lia at ~3000 cal. yr BP reflects descent of the timberline. A large mean July temperature decline between 3300 and 2800 cal. yr BP may have driven or at least contributed to the descent of the Picea abies–P. cembra forests. An increase in human indicator pollen types in Lake Bucura around 4200 cal. yr BP may reflect human impact in the naturally open alpine zone in the Late Bronze Age. In contrast, human impact likely appeared considerably later, around 2650 cal. yr BP (Early Iron Age) around Lake Lia in the upper subalpine zone. Human impact likely intensified after 2200 cal. yr BP at both sites that resulted in the lowering of the krummholz zone. We conclude that climate change and human impact both played an important role in the lowering of the treeline and timberline in the late-Holocene.

A multi-proxy approach is widely used for reconstructing climatic change in alpine lake sediments. This study applied bulk sediment geochemistry to reconstruct lateglacial and early Holocene climatic change in a glacial lake (Lake Brazi, 1740 m a.s.l.) in the Retezat Mts. (South Carpathians, Romania). The lowermost 1 m part of a 4.9-m long sediment core, covering the period between 9950 and 15,750 cal BP, was used for high resolution bulk analysis of major elements (Al 2 O 3 , SiO 2 , TiO 2 , CaO, MgO, K 2 O, Na 2 O, Fe 2 O 3 , MnO, SO 3 ). Linear discriminant analysis (LDA) was used to compare a priori classified main chemical groups. Subsamples from the core were priory ordered to “warm” and “cold” groups respectively, according to their age and evidence of cold and warm events in the record, as suggested by proxy correlation with the lateglacial event stratigraphy of North Greenland Ice Core Project (NGRIP). The discriminant function was calculated using concentrations of Al 2 O 3 , TiO 2 , CaO, MgO, K 2 O, Na 2 O, Fe 2 O 3 , and MnO after log ratio transformation. Loss-on-ignition, silicon and sulphur concentrations were not used for the discriminant analysis, but regarded as comparison proxies for checking up the validity of outputs. Sediments deposited during “cold” and “warm” events were separated significantly by the LDA function; 85.1% of the originally grouped cases were correctly classified under the LDA analysis. The calculated discriminant scores indicated four “cold” and four “warm” events. Sediments ordered into the “warm” group contained larger amounts of organic matter and sulphur, while sediment samples of the “cold” group were characterized by the overall predominance of major oxides bound into inorganic silicates. The discriminant scores showed strong correlation with the NGRIP δ 18 O data ( r = 0.8135) and with the pollen percentage sum of trees and shrubs ( r = 0.9460). Loss-on-ignition showed a somehow weaker, but still conclusive linear relationship with the discriminant scores ( r = 0.7505). Discriminant analyses of bulk sediment major oxide chemical data may be a useful tool to identify the impact of climatic events upon the nature and composition of materials delivered to a lake basin.

Multi-proxy, high-resolution analyses (lithological, geochemical, environmental magnetism) anchored by 22 14C dates, of a 5.53 m long sediment core from Lake Ighiel (Romanian Carpathians, central-eastern Europe) allowed the reconstruction of key local, catchment-lacustrine dynamics and an appraisal of palaeohydrological and palaeoclimatic gradients acting regionally over the last 6000 years. The first sedimentological phase of the record from 6030 to 4200 cal yr BP is characterised by low productivity and high detrital input indicating surface runoff processes due to enhanced rainfall. This interpretation is in agreement with other hydrological reconstructions reporting increased precipitation also in CE Europe, NE Mediterranean and also inferred summer and winter latitudinal temperature gradients (LTG) (as defined by Davis and Brewer, 2009), showing a strong connectivity between basin-lacustrine dynamics and the establishment of the dominant, Atlantic atmospheric circulation pattern in the area. The lacustrine system was more stable between 4200 and 2500 cal yr BP when clastic inputs diminished and biological productivity increased. During this interval, the coherence of Lake Ighiel's multi-century detrital events, identified in a range of proxy-data (albeit different in frequency and magnitude), with flood activity in central Europe (the Alps) suggests a common moisture forcing (Atlantic and periodically Mediterranean influences). In contrast, different reconstructions from the NE Mediterranean indicate a distinct NW-SE hydro-climatic gradient. A more complex and variable trend is depicted in Lake Ighiel sedimentation during the last ~ 2500 years showing a variable detrital trend likely reflecting an intriguing hydrological pattern which is in agreement with intervals of increased aridity phases during a generally moister period. Comparing our sedimentological results with published pollen records from the nearby area clearly indicates anthropogenic imprints during the Dacian-Roman Period and especially from the Middle Ages towards the present. The ~ 6000-year long sedimentary record of Lake Ighiel contributes to our understanding of mid and late Holocene palaeohydrological changes in the Carpathians and highlights the importance of latitudinal gradients in driving hydrological variability in continental Europe.

We assessed contamination in the Upper Tisza region (Hungary, Central Europe), analyzing the elemental concentrations in sediment cores of oxbows. Our hypothesis was that the metal contamination which occurred in the year 2000 and which came from the mining area in Transylvania (Romania) may be detected even 15 years after the contamination, based on the vertical profile of sediment cores. Sediment cores were collected from five oxbows, and the following elements were measured with microwave plasma-atomic emission spectrometry (MP-AES): Cu, Cr, Ba, Fe, Mn, Pb, Sr, and Zn. Among the oxbows studied, there was one protected oxbow, three were used for fishing, and one was contaminated with sewage. Our results indicated that the year of contamination is still observable in the vertical profile of the sediment cores. The pollution index (PI) was used to characterize the sediment enrichment of metal elements in the sediment cores. In the case of Cu, Pb, and Zn, the contamination which originated in the year 2000 was detected in the layers of the sediment cores. The contamination levels of Cu, Pb, and Zn were high or moderate in the studied oxbows. All oxbows were moderately contaminated by Mn, while a moderate level of contamination was found for Fe in the protected oxbow, one fishing oxbow, and the sewage-contaminated oxbow. In the fishing oxbows, a low level of contamination was found for Fe. The contamination level of Sr was low in the protected oxbow and in the two fishing oxbows, while in one of the fishing oxbows and in the sewage-contaminated oxbow, a moderate level of Sr contamination was found. The pollution index scores indicated that the contamination level for Ba and Cr was low in the sediment cores of the oxbows studied. Our results indicated that the contamination of the Tisza River from the mining area in Northern Romania has been continuous and is still ongoing.

In the frame of PROLONG (Providing long environmental records of Late Quaternary climatic oscillations in the Retezat Mountains) project lake sediment records were studied to reconstruct climate changes in the Southern Carpathians. During 2007 and 2008 summer long sediment cores were obtained from four glacial lakes (Lia, Bukura, Gales and Brazi) in the Retezat Mts (Southern Carpathians, Romania). Here we report the chronology and inorganic geochemistry from these lakes

The most recent, mainly explosive eruptions of Ciomadul, the youngest volcano in the Carpatho-Pannonian Region, have been constrained by detailed field volcanological studies, major element pumice glass geochemistry, luminescence and radiocarbon dating, and a critical evaluation of available geochronological data. These investigations were complemented by the first tephrostratigraphic studies of the lacustrine infill of Ciomadul's twin craters (St. Ana and Mohos) that received tephra deposition during the last eruptions of the volcano. Our analysis shows that significant explosive activity, collectively called EPPA (Early Phreatomagmatic and Plinian Activity), started at Ciomadul in or around the present-day Mohos, the older crater, at ≥ 51 ka BP. These eruptions resulted in a thick succession of pyroclastic-fall deposits found in both proximal and medial/distal localities around the volcano, characterized by highly silicic (rhyolitic) glass chemical compositions (ca. 75.2–79.8 wt.% SiO2). The EPPA stage was terminated by a subplinian/plinian eruption at ≥ 43 ka BP, producing pumiceous pyroclastic-fall and -flow deposits of similar glass composition, probably from a “Proto-St. Ana” vent located at or around the younger crater hosting the present-day Lake St. Ana. After a quiescent period with a proposed lava dome growth in the St. Ana crater, a new explosive stage began, defined as MPA (Middle Plinian Activity). In particular, a significant two-phase eruption occurred at ~ 31.5 ka BP, producing pyroclastic flows from vulcanian explosions disrupting the preexisting lava dome of Sf. Ana, and followed by pumiceous fallout from a plinian eruption column. Related pyroclastic deposits show a characteristic, less evolved rhyolitic glass composition (ca. 70.2–74.5 wt.% SiO2) and occur both in proximal and medial/distal localities up to 21 km from source. The MPA eruptions, that may have pre-shaped a crater similar to, but possibly smaller than, the present-day St. Ana crater, was followed by a so far unknown, but likewise violent last eruptive stage from the same vent, creating the final morphology of the crater. This stage, referred to as LSPA (Latest St. Ana Phreatomagmatic Activity), produced pyroclastic-fall deposits of more evolved rhyolitic glass composition (ca. 72.8–78.8 wt.% SiO2) compared to that of the previous MPA stage. According to radiocarbon age constraints on bulk sediment, charcoal and organic matter from lacustrine sediments recovered from both craters, the last of these phreatomagmatic eruptions – that draped the landscape toward the east and southeast of the volcano – occurred at ~ 29.6 ka BP, some 2000 years later than the previously suggested last eruption of Ciomadul.

the Retezat Mountains, this study discusses radiocarbon chronology and sediment accumulation rate changes in two sediment profiles in relation to lithostratigraphy, organic content, biogenic silica and major pollenstratigraphic changes. A total of 25 radiocarbon dates were obtained from sediments of two lakes, Lake Brazi (TDB-1; 1740 m a.s.l.) and Lake Gales (Gales-3; 1990 m a.s.l.). Age-depth modeling was performed on TDB-1 using calibrated age ranges from BCal and various curve-fitting methods in psimpoll. Our results suggest that sediment accumulation began between 15,124–15,755 cal yr BP in both lakes and was continuous throughout the Late Glacial and Holocene. We demonstrated that local ecosystem productivity showed delayed response to Late Glacial and Early Holocene climatic changes in the subalpine and alpine zones most likely attributable to the cooling effect of remnant glaciers and meltwater input. However, regional vegetation response was without time lag and indicated forestation and ...

A high-resolution paleolimnological record from Lake Brazi (TDB-1; 45°23’47″N, 22°54’06″E, 1740 m a.s.l.), a small, glacial lake in the Retezat (South Carpathian Mountains, Romania) provides a sensitive record of the impacts of late glacial climatic change on siliceous algal assemblages. The sequence, ranging from 15,700 cal yr BP to 9500 cal yr BP, suggests that the most significant changes in diatom assemblages took place at 12,800 and 10,400 cal yr BP, when alkaliphilous fragilarioid taxa were replaced by acidophilous diatoms. Altogether eight zones were distinguished with sharp and rapid changes of diatom assemblages. The paper discusses the application of siliceous algae in multi-proxy paleolimnological analyses, demonstrates the advantages and disadvantages of this proxy and presents the story of floristic discovery of unique diatom assemblages, the closest recent analogs of which are found in the arctic region.