LOESSFEST'09 | Aug. 31st – Sept. 3rd, 2009 |Novi Sad-Serbia
Anything New From Loess?
Ludwig Zöller1
1University of Bayreuth, Chair of Geomorphology, 95440 Bayreuth, Germany
The “Loessfest 99” in Bonn and Heidelberg, Germany, witnessed great progress in international loess research (see, e.g., Earth Science Reviews 54, 2001, and Quaternary International 76/77, 2001). The triumphal procession of the consistent Chinese loess stratigraphy, which was convincingly correlated to the marine isotope stratigraphy, had continued not only in China but also in other parts of Asia and started to enter Europe and to combine with Kukla`s stratigraphic scheme. Considerable progress in numerical and relative Quaternary dating methods was arising together with their new emerging problems. A number of new paleobiological and isotopic proxies for deciphering climate change in long loess sections were developed and applied. Refined stratigraphies, in particular of the last glacial cycle in loess, were more and more presented on a regional scale but suffered from unproven or speculative correlations. The search for loess equivalents of “Heinrich Layers” and D/O-cycles spread pandemic-like over the loessworld. Long loess-paleosol records arrived to their recognition as most valuable terrestric paleoclimate archives, face to face with marine and ice records.
Did, thus, loess research at the onset of the 3rd millennium AD enter from the rank of fundamental research into the rank of applied research?
The past decade not only presented a lot of confirmation for the state-of-the art in 1999. In my eyes the progress in loess research achieved during the past decade can be seen in both, regional and interregional correlation, respectively, and methodological progress.
The proof of plateau loess in the Carpathian Basin spanning at least the past 800 ka opens the door to the application of the basics of the Chinese loess stratigraphy in Europe. More and more “missing links” in between the Chinese Loess Plateau and Europe have been found, e.g. in Asian parts of the Eurasian loess belt, but also in Iran, thus improving interregional to intercontinental correlations. As a result of this, interregional gradients of terrestrial paleoclimate evolution could be pointed out. Surprisingly for some researchers but expected by others, similar patterns of loess-paleosol sequences and related paleoclimates were detected over long continental to intercontinental distances, e.g. 2 and S5, respectively. Spatially seen, loess-paleosol-sequences substitute hundreds of marine cores on the continents as an essential requisite to reconstruct atmospheric paleocirculation on the time axis, as was first achieved for the East Asian monsoon but can now be completed on a hemispheric scale. Although the illustration is by far not yet complete for Eurasia loess research is on a promising way for this northhemispheric super-continent. Comparable data for North America are now being completed, and more and more data from long loess-paleosol sequences in South America and Australia are emerging despite existing dating problems. It must not remain unmentioned that so-called “desert loess” or better “desert margin loess” since its first reference by Yaalon (1967) has been carefully investigated in and off Africa, Southern Iran, and in South America in the past years (see, e.g., Quaternary International 196, 2009), even if some profiles formerly regarded as “tropical loess” are now interpreted as weathering mantles (Morrás et al. 2009) and even if long continuous sequences re hardly found.
Refined loess stratigraphy of the last glacial-interglacial cycle originally focussed on western and Central Europe, probably because of the stronger influence of North Atlantic climatic oscillations known as Dansgaard- Oeschger cycles. In recent years not only the regional stratigraphies in these areas could be refined even more (down to millennial, centennial or even decadal resolution as in the ELSA archive of laminated maar sediments; Sirocko et al. 2006, Sirocko 2009) but also extended to the extra-Carpathian area and to Western Siberia (Haesaerts et al, subm.) and correlated with high resolution global records based on refined dating methods.
Quaternary dating methods in general have developed rapidly during the past decade. Luminescence dating in particular is most important for loess research and has been able to reduce error bars by applying the “SAR” protocol. Furthermore, there is a recent trend again to overcome the mysterious “100 ka limit” in luminescence dating of loess and other sediments. Several approaches are presently in an experimental stage with different success so far, but I am convinced that significant progress will emerge in the next years. From ESR dating new approaches to date quartz from aeolian and fluvial sediments are being tested, too. Molluscs embedded in loess or loess-like sediments have been subjected to comparative ESR, TL and OSL dating studies (Suchodoletz et al., in prep.). Amino acid chronology from loess molluscs, though not a numeric dating technique, has been successfully applied to Upper and Middle Pleistocene loess in Eurasia and appears to become a powerful tool for regional and interregional correlation.
Paleo- and rock magnetism is nowadays an inevitable method for advanced loess research. In recent years these methods have developed fast-paced. More sophisticated techniques to isolate the stable remanent magnetism not only improved the reliability of apparent magnetic reversals in sediments but are now able to provide data sets on the intensity of the paleomagnetic field recorded in loess which can be matched to the GLOPIS curve (actually available for the past 75 ka) for dating purposes (Hambach). Several rock magnetic parameters not only allow for a high resolution sequence stratigraphy to be matched to well-dated records such as NGRIP but also provide paleoenvironmental information. Thus, they serve as both, relative dating tools and paleoenvironmental proxies. From some loess sections in, e.g., Eastern Europe pollen grains have been successfully extracted and used for paleoenvironment reconstruction and for stratigraphic dating. Due to the scarcity of paleobiological remains in loess, however, stable isotopes from organic matter are used for this purpose, too. A most recent approach is the extraction of stable organic biomarkers (n-alkanes, lignin) and their specific stable isotopes analyses. First results from the Carpathian Basin yield some surprising results which deserve further attendance and may require a revision of existing assumptions on paleovegetation in glacials and interglacials (Buggle, Zech).
This presentation can, of cause, mention only a small part of world-wide loess research during the past decade. It may be sufficient, however, to answer the question in the title. Yes, there is a lot of news from loess, and there will be a lot more in the coming years.