Till stratigraphy in southern and western Finland

Abstract

This paper gives a review over the recent discoveries and results of Quaternary stratigraphical studies in southern and western Finland. The study of Quaternary stratigraphy has been very active and both Quaternary departments in Universities and Geological Survey of Finland as well as single geologists from Finland and abroad have contributed to the study of interglacial and interstadial stratigraphy this area. Main questions solved and to be solved is the relationship between the lithostratigraphy of last deglaciation and stratigraphy of earlier Pleistocene glacial i.e. Weichselian glaciations and Saalian glaciations. The active ice lobes during last deglaciation, their withdrawals and advances have deposited glaciofluvial and waterlain sediments which are covered by till formations. Ice lobes have eroded much of the »older» stratigraphy and information of the earlier Pleistocene glacial is fragmentary. Organic interglacial and interstadial sediments between till formations in Lapland and western Finland have made it possible to correlate till stratigraphy to larger areas and over national borders. Organic interglacial and interstadial sediments are so far missing from southern Finland. One of the crucial questions to be solved is the glaciations of the Early Weichselian substage and their unknown extend to northern, western or southern Finland. The length of the probable ice free period between Saalian deglaciation and the first Weichselian ice advance after the Weichselian interstadials to Ostrobothnia is unknown. Recent discoveries of interglacial and interstadial sediments older than Eemian interglacial have erased questions of the uniformity of Saalian glaciation here up North and questions of climatic and hydrographic development under Holsteinian interglacial in southern and western Finland. A synthesis is given of the Pleistocene stratigraphy in southern and western Finland. Stratigraphic work goes ahead very quickly and study of the deep depressions in bedrock and their thick Pleistocene sediments gives certainly more light to the Pleistocene development in southern and western Finland in the future. There is need for comprehensive Pleistocene stratotypes from the main glacial stratigraphy of Pleistocene glacial and lithostratigraphy of last deglaciation from southern and western Finland.

Keywords

• stratigraphy
• till
• deglaciation
• glaciation
• ice-marginal features
• interglacial environment
• interstadial environment
• Pleistocene
• Finland