Title screen

Some years ago an unusual and unexpected anomaly of magnetic susceptibility (MS) was observed in sediments of the upper course of the karstic Dobra River (Croatia) during preliminary measurements of MS throughout the Kupa River drainage basin [1, 2]. In that study, following techniques have been used: magnetic susceptibility and Curie temperature, isothermal remnant magnetism (IRM), mineralogical analysis (using XRD) and chemical analysis (using ICP-MS). Thermomagnetic curves showed a distinctive Curie-point of magnetite at 580 °C, while additional transformation observed at 520–560°C derives from titanomagnetite. Magnetic particles from the Dobra River sediments contain pyroxene, plagioclase, hematite and quartz, in addition to magnetite. The ratio Ni/Fe versus Cr/Fe suggests that the magnetic spherules are most probably impactites. New and exciting finding of magnetic spherules in sediments of this karstic river deserved further field and laboratory research, which continued in collaboration with Virginia Commonwealth University (VCU), USA.