Southwestern Finland was covered by the Weichselian ice sheet and experienced rapid glacio‐isostati c rebound after early Holocene deglaciation. The present mean overall apparent uplift rate is of the order of 4–5 mm/yr, but immediately after deglaciation the rate of crustal rebound was several times higher. Concurrently with land uplift, relative sea level in the Baltic basin during the past more than 8000 years was also strongly affected by the eustatic changes in sea level. There is ample evidence from earlier studies that during the early Litorina Sea stage on the southeastern coast of Finland around 7000 yr BP (7800 cal. yr BP), the rise in sea level exceeded the rate of land uplift, resulting in a short‐lived transgression. Because of a higher rate of uplift, the transgression was even more short‐lived or of negligible magnitude in the southwestern part of coastal Finland, but even in this latter case a slowing down in the rate of regression can still be detected. We used evidence from isolation basins to obtain a set of 71 14C dates, and over 30 new sea‐level index points. The age‐elevation data, obtained from lakes in two different areas and located between c. 64 m and 1.5 m above present sea level, display a high degree of internal consistency. This suggests that the dates are reliable, even though most of them were based on bulk sediment samples. The two relative sea‐level curves confirm the established model of relatively gradually decreasing rates of relative sea‐level lowering since c. 6100 yr BP (7000 cal. yr BP) and clearly indicate that the more northerly of the two study areas experienced the higher rate of glacio‐isostati c recovery. In the southerly study area, changes in diatom assemblages and lithostratigraphy suggest that during the early Litorina Sea stage (8300–7600 cal. yr BP) eustatic sea‐level rise exceeded land uplift for hundreds of years. Evidence for this transgressio n was discovered in a lake with a basin threshold at an elevation of 41 m above sea level, which is markedly higher than any previously known site with evidence for the Litorina transgression in Finland. We also discuss evidence for subsequent short‐term fluctuations superimposed on the main trends of relative sea‐level changes.
Four morphogenic types of the First Salpausselkä can be distinguished in the Lohja area: glaciofluvial marginal deltas, incompletely developed deltas, other ridges and hills, and formations with a rock core. The primary morphology has been considerably deformed by shore action during the stages of the Baltic Ice Lake, the Yoldia phase and the Ancylus Lake of the ancient Baltic. The Salpausselkä is composed of glaciogenic waterlain sediments, consisting of well-washed and sorted delta beds of sand and gravel, and of poorly sorted till layers. This Salpausselkä till was deposited partly as subaquatic flow till or subglacial meltout till from the debris-loaded ice margin in the proximal part of the formation. The distal and central parts of a typical marginal delta are characterized by undeformed regular flow (delta) structure. The proximal part often contains heterogeneous material, is complicated in structure and has been deformed mainly by glaciotectonic and load deformation structures, such as flow and load casts, faults and folds. The First Salpausselkä has a complex polygenetic genesis. It was formed in several phases at the ice margin, mainly under subaquatic glaciolacustrine conditions at the same time as the water level of the Baltic was gradually rising from a low level to the highest level of the Baltic Ice Lake, B 1. The stratified core and distal strata were deposited first, and then the heterogeneous proximal sediments under conditions associated with a floating and oscillating ice margin before the final retreat of the ice. The trend of deglaciation within the Salpausselkä belt is closely connected with the genesis of these ice-marginal formations. The general position and formation of the Salpausselkä seem to have been controlled primarily by climatic and topographic factors.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.