Ice‐marginal sedimentation and its implications for ice‐lobe deglaciation patterns in the Baltic region: Pohjankangas, western Finland

The sedimentary architecture of Pohjankangas, an elongated ridge formed of glacial meltwater deposits, is presented from investigation of four areas between Kankaanpää and Nummijärvi. This demonstrates a marked change in sediment input direction, indicating that the southern part of the ridge is neither an esker nor an interlobate accumulation, as thought previously. It is a subaquatic, ice‐contact fan moraine deposited from the west into the early post‐glacial Baltic basin Yoldia Sea–Ancylus Lake. The northern part of the ridge is classified as a beaded esker and this passes into the fan moraine complex at Elliharju. This investigation shows that the southern portion of Pohjankangas accumulated in a glacial bay when the eastern (Näsijärvi–Jyväskylä) ice‐lobe had already retreated further north. These findings emphasise the value of detailed investigation of the internal structure of landforms to understand fully the evolution of ice‐lobe patterns and the timing of their relative movements during deglaciation.