Ludwig Zöller

High-resolution chronologies for loess: comparing AMS 14C and optical dating results

The NuXloch loess section in South West Germany is famous in Central Europe for its thick deposits from the Last Glacial Maximum. It has therefore been intensively studied during the past few years and offers an excellent opportunity to compare the performance of different dating techniques covering the period 15–45 ka. Here we present results fromoptical and AMS 14 C dating. The silt-sized polymineral fraction of the clastic sediments and a multiple-aliquot approach was used for IR-OSL dating. 14 C dating was carried out on organic macro-remnants and humin fractions extracted fromthe sedim ents. With the exception of samples taken from the uppermost 1.5 m of the section, IR-OSL and calibrated 14 C-AMS ages are consistent over the entire period. The inconsistencies in the upper meters are thought to be due to disturbances during soil formation in the Holocene. The good agreement obtained on the remaining sequence demonstrates the high accuracy of both methods when studying loess sections: for the IR-OSL ages no significant age underestimations are obvious. The results clearly document that accurate chronologies can be developed for such continental sedimentary sequences. This gives access to archives that can now be studied with a high temporal resolution and allows the establishment of new paleoclimatic proxies for the study of terrestrial responses to past climatic changes. r 2003 Elsevier Science Ltd. All rights reserved.

Towards a revised chronostratigraphy of loess in Austria with respect to key sections in the Czech Republic and in Hungary

Abstract The stratigraphic ages of some well-known and characteristic paleosols in Austrian and Hungarian loess sections have been questioned by several workers since the mid-1970s. In particular, a generally accepted correlation of Austrian and Hungarian loess stratigraphies with the well-established Czech loess stratigraphy has not been put forward. This paper presents 41 new thermoluminescence (TL) dates and the first results from amino acid chronology of key sections in these areas. The results are in agreement and suggest a new interregional correlation of loess-paleosol sequences. For loess older than the last interglacial, quartz and feldspar inclusions yield more reliable TL ages than the polymineralic fine grain fraction.

δ13C variations of loess organic matter as a record of the vegetation response to climatic changes during the Weichselian

This paper presents high-resolution records of 13 C/ 12 C ratios of organic matter from two loess sequences in northwestern Europe. Our analysis is the first attempt to use organic matter δ 13 C as a record of the response of vegetation to climatic variations in an area where climatic changes were not strong enough to induce a radical change in vegetation cover. Over the last climatic cycle, the vegetation of the Rhine Valley showed a strong predominance of C3 plants. Thus, the small δ 13 C variations, with an amplitude of only 1.5‰ to 3‰, are interpreted as corresponding to fluctuations in water supply and atmospheric CO 2 concentration variations rather than to the ratio of C4 to C3 vegetation. Furthermore, loess sequences accumulated at high rates and allow high correlation with climatic proxy data, like the Greenland Ice Sheet Project 2 (GISP2) δ 18 O and the variations in CO 2 concentration recorded in the Vostok ice core. The δ 13 C constitutes a reliable and complementary proxy to study small climatic stresses endured by vegetation during the Weichselian in northwestern Europe. Moreover, by using absolute age control and correlations between global (Vostok-CO 2 ) or semi-global (GISP2-δ 18 O) climate effects, δ 13 C values of organic matter in loess sequences offer a new tool to establish a refined chronology in continental sequences.

Aeolian dust dynamics in central Asia during the Pleistocene: Driven by the long‐term migration, seasonality, and permanency of the Asiatic polar front

Loess-paleosol sequences preserve detailed archives of climate change, reflecting the dynamics of aeolian dust sedimentation and the paleodust content of the atmosphere. The detailed investigation of particle size distributions (PSDs) of windblown sediments is an increasingly used approach to assess the paleorecord of aeolian dust dynamics. The central Asian loess belt offers the potential to reconstruct Pleistocene atmospheric circulation patterns along an adjacent west-east transect within interior Eurasia through granulometric studies. In this study we present the aeolian dust record of the loess sequence at Remisowka (SE Kazakhstan), which reflects a detailed signal of glacial-interglacial climate and atmospheric dynamics in central Asia. On the basis of radiocarbon and amino acid geochronologic data, long-term semicontinuous trends in the aeolian dust record of the Last Glacial Cycle are observed and interpreted to reveal their paleoclimate signal. In consideration of the modern synoptical atmospheric circulation patterns and aeolian dust transport in central Asia, it is likely that the observed trends reflect the long-term migration, seasonal duration, and permanency of the polar front during the late Pleistocene. Previously published models, which focused on the reciprocal glacial-interglacial influence of the zonal Westerlies and the Asiatic high on the aeolian dust transport in central Asia, were overly simplified and should be modified to include the major influence of the Asiatic polar front. As the polar front activity is intimately connected with the development and position of the interhemispherically active, high-level planetary frontal zone (HPFZ), the presented data give insight to long-term aeolian dust dynamics and climate variability of interior Eurasia, which are linked with interhemispheric climates.

Loess in the Vojvodina region (Northern Serbia): An essential link between European and Asian Pleistocene environments

Loess in the Vojvodina region (Northern Serbia) : an essential link between European and Asian Pleistocene environments

The progressive evolution of a continental climate in southeast-central European lowlands during the Middle Pleistocene recorded in loess paleosol sequences

1 ABSTRACT Little is known about the long-term Quaternary climate evolution of central and south- east Europe, because suitable terrestrial paleoenvironmental records are scarce. We present a multiproxy record of loess paleosol sequences in the Middle and Lower Danube Basins over the past 700 k.y. In these lowlands, the continentality of interglacial climate progressively increased during the Middle Pleistocene. Corresponding trends are seen in other climate prox- ies in the same region and in the lowlands of the northern Black Sea, but not, or less clearly, in climate archives from outside these lowlands. We conclude that a small-scale increase in paleoelevation of central European mountain ranges (the Alps, Carpathians, and Dinarides) during the Middle Pleistocene might be the cause of the progressive increase in climate conti- nentality of southeast European lowlands.

New chronology and organic matter paleoclimatic significance of Nußloch loess sequence (Rhine Valley, Germany)

Abstract Due to its high accumulation rate, the loess sequence of Nusloch (Rhine Valley, Germany) is well suited to a high-resolution study of continental paleoenvironmental changes over the last climatic cycle for northwestern Europe. As carbon isotope ratios of plants depend on environmental variations, δ 13 C of loess-derived organic matter constitute reliable paleoclimatic proxies. We present here a new chronology of Nusloch loess sequence based on several 14 C and TL-dates. Our data show high correlations with global climate effects (Vostok-[CO2]) or semi-global (GISP2- δ 18 O ) and thus offer, in this way, a new approach to establish accurate chronologies in continental sequences. Furthermore, using a deconvolution of the δ 13 C signal would provide a quantitative proxy of moisture supply and permit paleoprecipitation reconstructions.

Thermoluminescence dating of loess—Recent developments

Abstract Thermoluminescence (TL) dating has developed into an important chronological method in loess research, especially beyond the range of radiocarbon dating. The principles and the present stage of the method applied to windborne sediments are summarized in this article. Advice to users is provided for appropriate sampling and handling of TL-samples as well as for measuring the natural radioactivity in the field. The potential and the limitation of loess TL-dating are discussed in terms of various case studies from Central Europe. In spite of the problem of age underestimation for old loess, TL-dating has already contributed greatly towards a better understanding of the loess stratigraphy and chronology. Thermoluminescence as a dating tool for archaeological samples has been established for 30 years. But the application of TL-dating to Quaternary sediments is — apart from some earlier attempts in the Soviet Union (Shelkoplyas and Morozov, 1965; Dreimanis et al., 1978) — a more recent development, essentially of the last decade (Wintle and Huntley, 1979). Since several review papers have already appeared on this subject (e.g. Wintle and Huntley, 1982; Mejdahl, 1986; Wintle, 1987; Singhvi and Wagner, 1986; Berger, 1988) the present contribution will only briefly mention the underlying TL-principles and the dating techniques, but will focus on the recent development in TL-dating of loess.

175 years of loess research in Germany—long records and “unconformities”

Abstract Loess research in Germany has a long tradition dating back to the early works of von Leonhard [von Leonhard, K.C., 1823/1824. Charakteristik der Felsarten. 3 Bde., 772 S. Heidelberg (J. Engelmann).] and his contemporary geoscientists. Ever since that time, German researchers and loess research within Germany have provided important contributions to the international ‘state of the art’. To date, however, perceptual “unconformities” have existed in both the continuity of loess research in Germany and the interpretation of the loess record in both the palaeoecological and the stratigraphic sense. This paper briefly highlights some relevant periods of loess research in Germany and the approaches adopted, from the early days to the present. The development of a refined stratigraphy of the last glacial loess in Germany during the second half of the 20th century is reviewed in the contribution by A. Semmel. Fundamental contributions were first published by Schonhals, Freising and Brunnacker. In the course of the subsequent work of the Loess Commission of the International Union for Quaternary Research (INQUA), the stratigraphy of the Wurmian loess has since been refined in almost all loess regions of Germany, and schemes consistent in their fundamental features have been published. In recent years, contributions have focussed on age determination, in particular those based on luminescence dating techniques.

Late Pleistocene loess and their paleosols in the Granada Basin, Southern Spain

Abstract The Granada Basin contains several sites that include Late Pleistocene loess. About seventy samples of fossil soils and sediments in six representative soil sequences were studied using palaeopedological methods. The results form a basis for a regional pedostratigraphy and a high resolution indicator of changing climate during the last interglacial/glacial cycle in the Western Mediterranean. Ten fossil soils of different ages show some similarity to the Middle European loess stratigraphy. It is thus inferred that there was a regular climatic sequence in this region during the Late Pleistocene with sedimentation during dry stadials and soil formation during wetter interstadials even in the sub-humid to semi-arid parts of Southern Spain.