Revised Middle and Late Pleistocene interglacial and interstadial records from the glaciated eastern Fennoscandia

Abstract

The Middle to Late Pleistocene palaeoenvironmental record from the repeatedly glaciated central and eastern Fennoscandia is poorly known. The majority of the glacial and warm interval records have been interpreted to represent only the last, Weichselian, glacial cycle (119–11.7 ka). We have revised the crucial part of the existing stratigraphic documentation in central and southern Finland. Our findings show that a considerable part of the depositional record extends further back in time and is more complete than previously thought. One record may reach the Middle Pleistocene Holsteinian Interglacial (≈MIS 11), 424-374 ka ago, and a large number of records are tentatively attributed to the Middle Pleistocene Röpersdorf-Schöningen Interglacial (≈MIS 7) 243-191 ka ago. During this possible Röpersdorf-Schöningen Interglacial, the Gulf of Bothnia hosted larger alkaline and smaller dystrophic lakes surrounded by boreal pine forests in a continental climate with warmer summers and colder winters than today. The Eemian (≈MIS 5e) 131-119 ka sea coastal records show detailed evidence of the widespread intermixing of continental fresh and marine waters. During the Early Weichselian Brörup Interstadial (≈MIS 5c) 109-96 ka, central and southern Finland seem to have supported open birch forest tundra, later invaded by spruce; not boreal pine forest as earlier thought. The early birch vegetation faced a tundra phase which may be the Montaigu cooling event c. 103 ka ago. The revised palaeoenvironmental interpretation shows that the development during the three discussed warmer intervals is well in line with the central European vegetational development. Our palaeoenvironmental interpretations concerning Röpersdorf-Schöningen and Brörup warm intervals are preliminary and will need further investigations. No indisputable Middle Weichselian (≈MIS 3, 57-29 ka) sedimentary record seems to have been recorded in the studied area.