ANCYLUS STAGE

early span of postglacial time in northern Europe marked by an impounding and freshening of the Baltic Sea Basin. The Ancylus stage, characterized by the common fossil snail genus Ancylus, lasted about 2,000 yearsfrom about 8,500 to 6,500 years ago. The Ancylus Lake was formed as a result of crustal uplift along the southwestern margin of the Baltic Basin, which was produced by the withdrawal of the thick continental ice sheet from the land. It probably attained its greatest size (larger than that of the present Baltic Sea, more than 160,000 square miles [414,000 square km]) about 6500 BC and then once again became a saline, ocean-connected body before 4500 BC, when the rising level of the sea, resulting from increased melting of the ice sheet, finally overflowed the land and once again made the Baltic an arm of the sea. At its maximum extent, the Ancylus Lake covered a large area of present Sweden and Finland. A rich fossil record, including pollen information, has provided a full history of the Ancylus Lake.