Palaeoenvironmental record of glacial lake evolution during the early Holocene at Sokli, NE Finland
Journal
Boreas
Journal Volume
43
Journal Issue
2
Pages
362-376
Date Issued
2014
Author(s)
Abstract
The development of a glacial lake impounded along the retreating, northeastern ice margin of the F ennoscandian I ce S heet during the last deglaciation and environmental conditions directly following the early H olocene deglaciation have been studied in NE F inland. This so‐called S okli I ce L ake has been reconstructed previously using topographic and geomorphologic evidence. In this paper a multiproxy approach is employed to study a 3‐m‐thick sediment succession consisting of laminated silts grading into gyttja cored in L ake L oitsana, a remnant of the S okli I ce L ake. Variations in the sediment and siliceous microfossil records indicate distinct changes in water depth and lake size in the L oitsana basin as the S okli I ce L ake was drained through various spillways opening up along the retreating ice front. Geochemical data ( XRF core‐scanning) show changes in the influence of regional catchment geochemistry (Precambrian crystalline rocks) in the glacial lake drainage area versus local catchment geochemistry ( S okli C arbonatite M assif) within the L ake L oitsana drainage area during the lake evolution. Principal component analysis on the geochemical data further suggests that grain‐size is an additional factor responsible for the variability of the sediment geochemistry record. The trophic state of the lake changed drastically as a result of morphometric eutrophication once the glacial lake developed into L ake L oitsana. The AMS radiocarbon dating on tree birch seeds found in the glaciolacustrine sediment indicates that L ake L oitsana was deglaciated sometime prior to 10 700 cal. a BP showing that tree B etula was present on the deglaciated land surrounding the glacial lake. Although glacial lakes covered large areas of northern F inland during the last deglaciation, only few glaciolacustrine sediment successions have been studied in any detail. Our study shows the potential of these sediments for multiproxy analysis and contributes to the reconstruction of environmental conditions in NE F inland directly following deglaciation in the early H olocene.
Type
journal article