Investigating soil magnetic properties with pedogenic variation along a precipitation gradient in loess-derived soils of the Golestan province, northern Iran

In the Golestan province in northern Iran extensive loess deposits, and widespread loess-derived soils crop out. While a strong precipitation gradient (200–700 mm per year) from North to South is characteristic, temperature differences are negligible (17–18 °C per year). Recently, many studies on loess-derived palaeosols and modern soils from this region were published; However, in these publications only limited information on the magnetic properties of loess and loess-derived soils is given, nor the potential of these properties to be applied as proxies for palaeoclimate reconstruction. In order to study soil magnetic properties along the precipitation gradient in the Golestan province, six pedons of modern soils were selected. The physicochemical properties, the clay mineralogy and magnetic parameters of soil samples were analysed. Susceptibility measurements (20.2–130.77 × 10−8 m3kg−1), ARM susceptibility values (0.00489–0.068 m3kg-1), IRM values (0.0027–0.0105 Am2kg−1), and hysteresis measurements provide significant evidences for an increase of the content of fine grained ferromagnetic minerals with increasing mean annual precipitation. Simultaneously, the amount of SP sized particles increase. Magnetite, maghemite, and hematite are the major magnetic minerals in the studied samples, whereby magnetite seems to be dominant in the soils of the loess plateau of northern Iran. By presenting data from this region of the northern Iran for the first time, another example is provided for the application of magnetic properties as proxies for the reconstruction of the paleoclimate. The results are compared to data of the Chinese loess plateau, the Russian steppe and loessic soils from the midwestern United State with similar relations of pedogenic susceptibility and MAP.