Grain size analysis and sedimentological characteristics of wind-blown sands: a case study of Barchan dunes in the Erg of Tabas, central Iran

The current study investigates the geological characteristics and wind-driven dynamics of barchan dunes in arid regions. We analyzed the depositional processes and particle size distribution of eight dunes located approximately one kilometer apart. The results indicate that silt (0.80 %), medium sand (8.67 %), coarse sand (1.34 %), and very fine sand (18.32 %) are less common than fine sand (69.55 %). Key grain-size statistics indicate that aeolian sediments are fine-grained and well-sorted, with a mean particle size of 2.64 ϕ, sorting value of 0.51 ϕ, skewness of −0.05, and kurtosis of 1.26. The grain size classification indicates a complex depositional history, with aeolian origin accounting for around 87.3 % and river characteristics for only about 12 %. Leeward slopes and bottom areas tend to deposit finer, better-sorted sediments and typically contain coarser, less-sorted material than windward slopes and crests because gravity settles and influences wind movement. Long-term wind measurements (1986–2024) indicate that the principal southeastward drift vectors are continuous northwesterly winds (RDD = 159.04°) and considerable sand transport (DP = 45.25 VU). A transitional aeolian regime, as indicated by the Sand Mobility Index (0.59), promotes the development of semi-stable barchan dunes with both unidirectional and multidirectional wind impacts. These results illustrate the intricate connections between dune formation, sediment supply, and wind regime. These findings highlight the complex relationships that exist between wind regimes, sediment availability, and dune formation. By integrating extensive sedimentological research with long-term meteorological monitoring, this study provides new insights into the dynamics of aeolian systems and a practical framework for predicting dune evolution.