Reconstructing Floodplain Evolution from Sedimentary and Geochemical Records: Oxbow Lake–Natural Levee Systems Along the Upper Tisza River

Floodplain oxbow lakes and natural levees preserve sedimentary archives that can provide information on long-term changes in depositional environments. This study investigates three oxbow lake–natural levee pairs of different ages along the Upper Tisza River using 258 sediment records. Grain size composition, pH, electrical conductivity, CaCO3-equivalent values, and organic carbon were characterized. Spearman correlation analysis was used to examine relationships among the measured properties, while principal component analysis (PCA) was performed using pH, electrical conductivity, organic carbon, and isometric log-ratio-transformed grain-size data. The profiles showed pronounced vertical and between-site heterogeneity, indicating that geomorphological position alone does not determine sediment properties. PCA identified four major sedimentological and geochemical gradients, whereas cluster analysis distinguished four broad sediment groups with distinct sedimentological and geochemical characteristics. These multivariate statistical analyses revealed relative vertical zonation and sedimentological and geochemical changes associated with oxbow-lake infilling and natural-levee development. Long-term mean sediment accumulation rates were estimated separately from the multivariate analyses using sediment thickness, documented channel-cutoff ages, and, where applicable, stratigraphic correlations. Time-averaged post-cutoff oxbow-lake sediment accumulation rates were approximately 10.2 cm yr−1 for GYM1, 4.56 cm yr−1 for GYM2, and ≤4.62 cm yr−1 for GYM3. For the natural levees, no accumulation rate was estimated for GYF1 because of the absence of an independent chronological marker, whereas tentative correlation of buried paleosol horizons in GYF2 and GYF3 with dated paleosols on the Bereg Plain suggests conditional long-term mean accretion rates of approximately 0.042–0.090 cm yr−1 for GYF2 and 0.032–0.069 cm yr−1 for GYF3, respectively. Integrating vertical sedimentological and geochemical records with multivariate statistical analyses and independent chronological and stratigraphic constraints therefore provides a framework for reconstructing relative depositional succession and estimating long-term sediment accumulation during floodplain evolution.