Abstract: Mikulinian (Eemian) marine deposits are widespread in the northern Arkhangelsk Region, Russia. Shoreface deposits have been found in exposures along the Pyoza and Vaskha rivers; however, deposits of undoubtedly tidal origin have not hitherto been recognized there. By contrast, here we show that shells of Macoma balthica (Linnaeus, 1758) (Tellinidae, Bivalvia) unearthed from the shoreface deposits show growth patterns indicating that the bivalves lived in an environment affected by tidal periodicity. The periodicity was a mixed tide with significantly diurnal inequality in the height of the low waters. In the Arkhangelsk Region, the Mikulinian hydrodynamical conditions of the tidally influenced regime are still poorly known. Because the spatial and temporal distribution of M. balthica is broad in the fossil record, its shells have a large potential for tidal interpretations, as contribution to hydrological reconstructions.