On the geochemistry of the Late Quaternary loess deposits of Dobrogea (Romania)

Ten samples of loess and palaeosols collected from the Costinesti-Dobrogea (Romania) loess deposit and covering a time span of about 690 ± 90 ka were analyzed by X-ray diffraction, Instrumental Neutron Activation Analysis and X-ray Fluorescence in order to determine the origin as well as the climatic conditions during loess deposition. The presence of illite and calcite suggests reduced weathering, confirmed by climate proxies. Chemical Index of Alteration (54.6-64.0), Chemical Index of Weathering (65.7-71.7) and Rb/Sr (0.26-0.47) were lower than the neighboring Hungarian loess, but closer to the average loess. The content of 28 trace elements, including 10 REE, confirmed an average rock composition close to the Upper Continental Crust. The elevated content of Cr and Ni indicated the presence of a certain amount of felsic rock material. Zr and Hf whose content was more than twice that of the Upper Continental Crust indicate significant sediment sorting. The low values of climatic proxies as well as the absence of any statistical significant difference between loess and palaeosol material confirmed rather limited weathering during the formation of the south-eastern Dobrogea loess deposits.