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 forme d of glacial meltwater deposits, is presented from investigation of fo ur areas between Kankaanpaa and Nummijarvi. 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 deposi ted 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 accumul ated in a glacial bay when the eastern (Nasijarvi-Jyvaskla) ice-lobe h ad already retreated further north. These findings emphasise the value of detailed investigation of the internal structure of landforms to u nderstand fully the evolution of ice-lobe patterns and the timing of t heir relative movements during deglaciation.