The late Quaternary loess record of Tokaj, Hungary: Reconstructing palaeoenvironment, vegetation and climate using stable C and N isotopes and biomarkers

Abstract

Large areas of Southeast Europe are covered by Pleistocene loess deposits with interbedded palaeosol layers, reflecting interglacials or -stadials. These loess-palaeosol sequences are valuable terrestrial archives for continuous palaeoclimatic and palaeoenvironmental information. In recent years, the traditional paradigm of treeless full-glacial palaeoenvironments has increasingly been called into question, as there is palynological, anthracological and malacological evidence for the continuous presence of trees from loess-palaeosol sequences in the Carpathian Basin. This paper aims at contributing to this discussion by applying biogeochemical, geophysical and sedimentological methods to a late Quaternary loess-palaeosol profile at Tokaj, NE Hungary. Previous studies at the same location have focused on molluscs and charcoal, while this study concentrated on stable C and N isotopes and lipid biomarkers. Long-chain n-alkanes (C23-C33), which form major constituents of plant leaf waxes, have successfully been used as biomarkers over the last years and allow for a reconstruction of palaeovegetation based on the differentiation of grassland vs. shrubs and trees. Stable carbon isotopes were used to further differentiate between C3 and C4 palaeovegetation, and stable N isotopes to reconstruct the N 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 pedo- and biostratigraphy. Although the results do not agree in every detail with previous studies, there are surprising matches and similarities in the data. Alkane and stable N isotopic data indicate that, pedogenesis occurred under productive, fertile steppe-grasslands, probably in an intensified seasonal climate, and during reduced sedimentation. 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. This interpretation is also supported by previous mollusc data that provide evidence for several periods of favourable conditions for tree growth. © 2010 Elsevier Ltd and INQUA.