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

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 (approximate to MIS 11), 424-374 ka ago, and a large number of records are tentatively attributed to the Middle Pleistocene Ropersdorf-Schoningen Interglacial (approximate to MIS 7) 243-191 ka ago. During this possible Ropersdorf-Schoningen 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 (approximate to 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 Brorup Interstadial (approximate to 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 Ropersdorf-Schoningen and Brorup warm intervals are preliminary and will need further investigations. No indisputable Middle Weichselian (approximate to MIS 3, 57-29 ka) sedimentary record seems to have been recorded in the studied area. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

The study revises the existing stratigraphic records in central and eastern Fennoscandia, revealing a more complete and extended palaeoenvironmental history than previously thought. The findings suggest the presence of birch forest tundra during certain warm intervals, challenging the previous assumption of boreal pine forests in the region. Additional research is needed to further explore the warm periods and sedimentary records during the Middle Weichselian in the studied area.