ORIGINAL ARTICLE Origin and weathering of landslide material in a loess area: a geochemical study of the Kulcs landslide, Hungary Beatrix Udvardi 1 • Istva ´n Ja ´nos Kova ´cs 1 • Csaba Szabo ´ 2 • Gyo ¨rgy Falus 1 • Ga ´bor U ´ jva ´ri 3 • Aniko ´ Besnyi 1 • E ´ va Bertalan 1 • Ferenc Budai 1 • Zsolt Horva ´th 1 Received: 5 February 2016 / Accepted: 17 September 2016 Ó Springer-Verlag Berlin Heidelberg 2016 Abstract Geochemical characteristics of sediments are responses to physical and chemical alteration in landslides. However, consequences of in situ interactions associated with landslides are difficult to distinguish from those related to long-term weathering in young soft sediments such as loess. In this study, geochemical characteristics of the Kulcs landslide in Hungary are studied to identify the provenance of the loess–paleosol–red clay sequence and geochemical signatures that can potentially be attributed to the effects of landsliding. Results indicate that sliding is largely initiated by the lithological changes within the landslide body. Sedi- ments above the sliding zone closely resemble the non- slipped Pleistocene old loess deposits from Hungary. It is also confirmed that the sliding zone develops in old paleosols in the loess sequence and red clays at its base which are all characterized by the enrichment of Al, K, Na, H 2 O and considerable depletion in Ca and Mg associated with car- bonates. Altogether, these geochemical characteristics indicate that chemical weathering trend of unconsolidated landslide sediments is slightly modified by the redistribution of carbonates and decomposition of plagioclase. It is assumed that the distribution of Mn and Ba is modified by the water–sediment interaction in the landslide. Keywords Landslide Á Geochemistry Á Weathering Á Loess Á Red clay Introduction There are several laboratory experiments on the time-de- pendent geochemical alteration of sediments under different environmental conditions (e.g. Van der Salm et al. 1998; Erginal et al. 2009; Shoaei 2013; Jiao et al. 2014). Landslides are natural laboratories in which weathering processes are intensified due to the water–sediment interactions. However, landslides have rarely been studied from a geochemical perspective. In fact, landslides usually develop in weathered sediments, along pre-existing weak zones (Hutchinson 1988; Cruden and Varnes 1996). Thus, it seems to be challenging to identify landslide-induced changes in the geochemical composition of sediments if the geological and weathering history of the host material is poorly known in sediment layers prone to landsliding (Wen 2002). This is especially true for non-consolidated soft sediments, in particular for landslides occurring in loess regions. Loess and related sediments (paleosols, red clay) are aeolian dust deposits and affected by subsequent weathering and pedogenesis. These sediments extend over large areas in Asia, Europe, North America and parts of South America (Gallet et al. 1996). In these areas, it is questionable how to distinguish long-term alteration processes from the secondary effect of slidings. Geochemical studies on slip zones are very rare in the literature. Most of them focus on soil–bedrock contacts Electronic supplementary material The online version of this article (doi:10.1007/s12665-016-6103-6) contains supplementary material, which is available to authorized users. & Beatrix Udvardi udvardi.beatrix@mfgi.hu 1 Geochemical and Laboratory Department, Geological and Geophysical Institute of Hungary, Stefa ´nia u. 14, Budapest 1143, Hungary 2 Lithosphere Fluid Research Lab, Institute of Geography and Earth Sciences, Eo ¨tvo ¨s University, Pa ´zma ´ny Pe ´ter se ´ta ´ny 1/c, Budapest 1117, Hungary 3 Institute for Geological and Geochemical Research, Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences, Csatkai E. u. 6-8., Sopron 9400, Hungary 123 Environ Earth Sci (2016)75:1299 DOI 10.1007/s12665-016-6103-6