Miankaleh coastal barrier system was formed at a wave dominated coast with low offshore gradient in southeast of Caspian Sea, North of Iran. This sedimentary complex with 71 km length and 3 km average width is extended from West to East in Holocene period and formed Gorgan bay as the biggest one in Iranian coast of Caspian Sea. Prevailing winds between 270 and 315 degree with different speeds, storms, sea level changes and long-shore currents play an important role in sediment transport of this coastal barrier system. Core and trench information are combined with GPR profiles in geomorphology and sedimentary aspects. Khademlo GPR profile which is the major one with 1480 meters length is extended from Caspian Sea to Gorgan bay. Nine core and trench stations which were placed in this area, complete the data about formation of Miankaleh coastal barrier system. Radar facies and sedimentological information indicate dune cross bedding, swash lamination, spillover lobe, avalanche bedding, ripple bedding and runnel infill in the study area. Mean size average of analyzed sediments in core and trench subsamples vary from medium to fine sand size with tendency to fine sands. Lack of silt and clay units demonstrates absence of wash-over sediments in this system. Because geometry of sedimentary units and sediment textures show that sediment supply rate was more than sea level raise in Holocene period, Miankaleh coastal barrier system take place in prograding barrier and beach ridge complex category. Fore-dune ridges, fore-shore accretionary surfaces and low-relief ridges and swale topography in Khademlo section confirm beach ridge complex. Miankaleh coastal barrier system is compared with Lankoran and Kilyazi beach ridge complexes in Azerbaijan and Daghestan beach ridge complex in Russia as other samples of countries around the Caspian Sea.

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