The Caspian Sea is the largest land loked water body on earth,containing 40% of the earth’s continental water mass (Dumont, 1998) and is susceptible to environmental changes.The Caspian Sea has experienced different sea-level fluctuation (lahigani et al., 2009). In this survey, in order to sedimentological studies and determine the Caspian Sea level fluctuations by variations in magnetic susceptibilities of the Caspian bottom sediments, 7 cores with certain ditstances and depths have been taken by gravity corer method as well as surface samples from beach and river mouths of adjacent area were taken from southeastern basin in Noshahr-Tonekabon area of the Caspian Sea. These samples have been analyzed for grain size, total organic carbon content, carbonate content, mineral composition and magnetic susceptibility. The obtained results from physical and chemical analysis show that the sediments mainly composed of mud with homogenous texture. Grain size of the sediments decreas from the shoreline and carbonate and organic matter content also decreases. Camparing the mineralogy of marine sediments with fluvial inputs demonstrated that reverine source is the main supplier of the sediments. The results show a close relation between particle size distribution and magnetic susceptibility magnitude due to variation in detrital influx, caused by sea-level fluctuations in different time. This process is reflected in increasing particle size and magnitude of magnetic susceptibility simultaneously with sea-level rise and decreasing particle size and magnitude of magnetic susceptibility simultaneously with sea-level fall.
