The soil changes from east to west. The reddish-brown soil in the eastern part is 40 to 50 cm thick, with frequent blunt crinoidal limestone fragments (calcaire à Entroques). To the west, the light-colored soil is about as thick, but less stony, with some small oyster shells.Two different types of substratum underlie Les Bonnes Mares. In the eastern part, ocher limestone rich in debris from marine organisms (calcaire à Entroques) crops out in places, because there was once a quarry in this Grand Cru. In the upper quarter of the plot, to the west, this limestone is overlain by marls rich in small oyster shells (marnes à Ostrea Acuminata).