Igor Obreht

Tracing the influence of Mediterranean climate on Southeastern Europe during the past 350,000 years

Loess-palaeosol sequences are valuable archives of past environmental changes. Although regional palaeoclimatic trends and conditions in Southeastern Europe have been inferred from loess sequences, large scale forcing mechanisms responsible for their formation have yet to be determined. Southeastern Europe is a climatically sensitive region, existing under the strong influence of both Mediterranean and continental climates. Establishment of the spatial and temporal evolution and interaction of these climatic areas is essential to understand the mechanisms of loess formation. Here we present high-resolution grain-size, environmental magnetic, spectrophotometric and geochemical data from the Stalać section in the Central Balkans (Serbia) for the past ~350,000 years. The goal of this study is to determine the influence of the Mediterranean climate during this period. Data show that the Central Balkans were under different atmospheric circulation regimes, especially during Marine Isotope Stages 9 and 7, while continental climate prevailed further north. We observe a general weakening of the Mediterranean climate influence with time. Our data suggest that Marine Isotope Stage 5 was the first interglacial in the Central Balkans that had continental climate characteristics. This prominent shift in climatic conditions resulted in unexpectedly warm and humid conditions during the last glacial.

Shift of large-scale atmospheric systems over Europe during late MIS 3 and implications for Modern Human dispersal

Understanding the past dynamics of large-scale atmospheric systems is crucial for our knowledge of the palaeoclimate conditions in Europe. Southeastern Europe currently lies at the border between Atlantic, Mediterranean, and continental climate zones. Past changes in the relative influence of associated atmospheric systems must have been recorded in the region’s palaeoarchives. By comparing high-resolution grain-size, environmental magnetic and geochemical data from two loess-palaeosol sequences in the Lower Danube Basin with other Eurasian palaeorecords, we reconstructed past climatic patterns over Southeastern Europe and the related interaction of the prevailing large-scale circulation modes over Europe, especially during late Marine Isotope Stage 3 (40,000–27,000 years ago). We demonstrate that during this time interval, the intensification of the Siberian High had a crucial influence on European climate causing the more continental conditions over major parts of Europe, and a southwards shift of the Westerlies. Such a climatic and environmental change, combined with the Campanian Ignimbrite/Y-5 volcanic eruption, may have driven the Anatomically Modern Human dispersal towards Central and Western Europe, pointing to a corridor over the Eastern European Plain as an important pathway in their dispersal.

Late Quaternary environmental changes in Helambu Himal, Central Nepal, recorded in the diatom flora assemblage composition and geochemistry of Lake Panch Pokhari

This study presents changes in diatom flora assemblage composition, TOC, TOC/N and biogenic opal in a 450xa0cm core of Lake Panch Pokhari, Central Nepal (4,050xa0m asl), indicating Late Quaternary environmental fluctuations. Four Diatom Zones (DZ) were detected, with two major changes. The first one was found in ~430xa0cm depth (~14.8xa0cal. kyr BP), where the original flora characterized by Navicula digitulus Hustedt, Pinnularia rhombarea Krammer, P. aff. viridiformis var. minor Krammer, Encyonema silesiacum (Bleisch) D. G. Mann, Cymbopleura naviculiformis (Auerswald) Krammer and Nitzschia sp. was fully replaced by an assemblage consisting of Aulacoseira alpigena (Grunow) Krammer, Diatoma hyemalis (Roth) Heib., Tabellaria flocculosa (Ehrenberg) Kützing, Brachysira brebissonii Ross and Pinnularia subgibba Krammer, creating a stable diatom assemblage for ~8xa0kyr (DZ3). The second change was found at ~70xa0cm (~2.1xa0cal. kyr BP) when increased nutrient inputs lead to emergence of new taxa such as Fragilaria construens var. subsalina Hustedt, F. tenera (W. Smith) Lange-Bertalot, Eunotia cf. pseudopapilio Lange-Bertalot and M. Nörpel-Schempp and Gomphonema subclavatum Grunow. In order to evaluate the past environmental conditions in the Lake Panch Pokhari, the detected diatom taxa were subjected to analyses of their autecological preferences and dominance within the specific assemblage. We also assumed that TOC/N ratios >10 indicate accelerated erosion due to the strengthening of the Summer Monsoon starting at ~14.8 and between 13.7 and 12.8xa0cal. kyr BP. Monsoon intensity was most pronounced during the Early Holocene and at the beginning of the Late Holocene. The fluctuations of TOC and TOC/N in the Late Glacial sediments seem to correlate temporally and climatically with oscillations in the Northern Atlantic region.

New luminescence-based geochronology framing the last two glacial cycles at the southern limit of European Pleistocene loess in Stalać (Serbia)

Abstract A new geochronology was established for the Stalać loess-paleosol sequence (LPS) in Serbia. The section is located in the interior of the Central Balkan region, south of the typical loess distribution, in a zone of paleoclimatic shifts between continental and Mediterranean climate regimes. The sampled sequence contains four well-developed paleosol and loess layers, a crypto tephra and one visible tephra layer. Optically stimulated luminescence measurements showed a strong dependency of preheat temperature on equivalent dose for one fine-grained quartz sample, which makes it unsuitable for dating. A firm chronology framing the last two glacial cycles was established using fine-grained polyminerals and the post-infrared infrared stimulated luminescence (pIR50IR290) protocol instead. The characteristics of dated paleosols indicate similar climatic conditions during the last interstadial and interglacial phases, which were different from the penultimate interglacial period. The tephra within the L2 loess, probably related to tephra layers also found in other sections in Southeastern Europe, was sandwich-dated. The results indicate an age between 118 ka and 141 ka. Furthermore, a weak pedogenic layer dated to between 126 ka and 148 ka gives a first numerical age to this soil formation in Southeastern Europe.

Loess distribution and related Quaternary sediments in the Carpathian Basin

ABSTRACT Supraregional (palaeo)geoecological studies require detailed knowledge of the distribution of aeolian sediments and their sources. Such spatial data can be visualised and shared in maps, but often these are constrained in their resolution or extent. This is the case for the Carpathian Basin, where cross-border maps are not detailed enough to answer many research questions. Problems occur especially along political borders due to different geological mapping standards and varying lithological definitions. Using a Geographic Information System (GIS), we compiled a map showing the distribution of loess and related Quaternary sediments in the Carpathian Basin, with unprecedented detail. We vectorised and analysed existing data (mainly from geological maps) and combined and transferred these into a common (loess) sediment classification system. This cross-border map shows the distribution of aeolian sediments in the Carpathian Basin at a scale of 1:1,500,000. For the northwestern and the southern Carpathian Basin, we added maps that clarify the extent of late Pleistocene and Holocene terrace and floodplain deposits, which were merged in the Main Map to highlight the predominant dust source areas for this region.

Landscapes and Paleolandscapes in south-eastern Europe during LateQuaternary and their relevance for human habitats and dispersal

Pleistocene landscape dynamics affect climatic and environmental conditions, and may have had a major impact on modern human habitats. In this contribution, reconstructions of modern and late Pleistocene environments based on landscape evolution models are presented and discussed following a series of transects from the Pannonian Basin to the Black Sea. These transects include geomorphological features and landscapes like loess plateaus, dune fields, alluvial plains, the Carpathian Mountains, and their foothills. To enhance our understanding of anatomically modern human (AMH) habitats, transects of paleo-landscapes from the Carpathian Basin to the Black Sea coast are investigated, focussing on a time-interval of ca. 30,000-40,000 years ago and the last glacial maximum

Tracing the influence of Mediterranean climate on Southeast Europeduring the past 350,000 years

Although global patterns of past climate change are relatively well established at the scale of orbital forcing, local responses in various regions are still not understood. Loess-paleosol sequences (LPS) are valuable archives of past environmental changes in Southeast Europe. However, most LPSs seem to be limited in their sensitivity to paleoclimate due to an overall imprint of enhanced dryness in the region during loess sedimentation. Here we present the results from the Stalac section in the Central Balkans, one of the first high-resolution multiproxy LPS records spanning the past ~350,000 years in Southeast Europe

Environmental conditions on the corridor of human migration between 40,000 and 14,000 a BP in the Balkan region. A multi-proxy approach on loess-paleosol profiles

This contribution focuses on two PhD projects, which are integrated within the collaborative research centre 806 “Our way to Europe” at the University of Cologne and the RWTH Aachen University (Germany). The main research focus is the migration of anatomical modern human (AMH) to Europe. We concentrate on the paleoenvironmental conditions on the route through southeastern Europe. This links the region with the earliest fossils of Homo sapiens sapiens (so far known) in the Middle East, Anatolia, the Northwestern Black Sea, the Balkans and the Pannonian Basin. One PhD topic deals with the sedimentological and geochemical approach mainly from loess and loess-like sediments to reconstruct the paleoenvironmental conditions; the other PhD topic places an emphasis on the exact timing of those sedimentary records via luminescence dating. In particular the investigation of loess-paleosol sequences plays a central role. Geoarchives in Hungary, Serbia and Romania are of main interest for the project. The investigations will focus mainly on the loess and loess like sediments. However, data will be compared to further geoarchives, such as lacustrine sediments, speleothemes and marine records, to get a complete insight into the climatic evolution. First analyses include the loess-paleosol sequences at Bodrogkereztur (Hungary, east of Miskolz), Orlovat (Serbia, north of Belgrade), Sagvar (Hungary, southeast of Lake Balaton), and Stalac (Serbia, confluence of South and West Morava).

Towards mineral magnetic based millennial time scales in Late Pleistocene Danubian Loess-Palaeosol Sequences

The understanding of the climate system of the Earth’s, its present day state, and the prediction of its future states requires the detailed knowledge of its history. Sedimentary archives are the bases of almost any historical approach to the Earth’s climate system – the palaeoclimate research. Aeolian dust sediments (loess) are beside marine/lacustrine sediments, peat bogs and arctic ice cores the key archives especially for the reconstruction of the palaeoclimate in the Eurasian continental mid-latitudes. The Eurasian loess-belt has its western end in the Middle Danube (Carpathian) and the Lower Danube Basin. Like in the Chinese Loess Plateau and in the steppe areas of Central Asia and in the regions around the Caspian and the northern Black Sea one can find here true loess plateaus dating back more than one million years and comprising a semi-continuous record of the Quaternary palaeoclimate (Markovic et al. 2011, 2012).

Climatological and environmental change as derived from physical and geochemical loess sediment properties: Examples of last glacial loess sites from the Pannonian Basin

The Project B1 within the CRC 806 “Our way to Europe” is focused on the Eastern Trajectory of modern human migration from Africa into Europe. The Middle East, Anatolia, Balkans and Southeastern Europe constitute the principal areas to be investigated. Within these larger regions key areas were selected for combined archaeological and geoarchaeological research, fieldwork having delivered case studies for initial Modern Human adaptational systems, yet to be fully analysed. During the first stage of the B1 research programme (2009-2013), key areas were in Jordan (Wadi Sabra/Petra), in Romania (Upper Timis valley/Southern Banat) and in Ukraine (Doroshivtsy / Northern Bukovina, Chernivtsi region), all within the Marine Isotope stage (MIS) 3/2 time range. Thus, the first phase of the CRC focused on locations of Early Upper Palaeolithic sites in selected morphological positions, and specifically the upland-lowland comparative concept. It is anticipated to (1) intensify regional studies in the Serbian Banat and western Romania, now with a north-western extension in Hungary. Chronologically we continue research into later MIS 3 archaeological and geological archives (40,000 to 20,000 B.P.), now also extending the time range to late Middle Palaeolithic (e.g. Garandhal and Bukk), and reaching back to the earlier MIS 3 and MIS 4 time range.