Pre-late Weichselian podzol soil, permafrost features and lithostratigraphy at Penttilänkangas, western Finland

Abstract

The ridge-shaped Penttilänkangas accumulation in western Finland is glaciofluvial in origin: probably an ice-marginal subaquatic fan, reworked and covered with younger deep water, littoral, eolian and glacial sediments. Two cycles of glacial melting and land emergence to littoral and subaerial conditions can be distinguished at Penttilänkangas, separated by one glacial advance. Special attention is paid to a fairly well preserved buried podzol soil profile and to permafrost features. The podzol soil is interpreted as having developed in littoral sand and subsequently covered with eolian sand and till. The permafrost features are observable in all the sediments below the covering till, indicating prolonged periglacial ice-free conditions after the soil formation and before the latest glacial advance. The physical properties (content of <0.0625 mm fraction, magnetic susceptibility, colour, dry bulk density and LOI) of the buried podzol soil profile are compared to the Holocene podzol soil with similar parent material in the same area. These properties, as well as the identified microfossils and cell tissue, imply that the paleosol probably developed over a longer period and/or in similar or warmer and moister conditions than the Holocene soil. The podzolisation possibly initiated in the Eemian Stage (MIS 5e), and according to the OSL datings, it ceased in the beginning of the Middle Weichselian Substage (MIS 4). After that, ice-free permafrost conditions prevailed for several thousand years before the Weichselian ice-sheet advanced to western Finland around 65 ka at the earliest.

Lithostratigraphy and Optically Stimulated Luminescence age determinations of pre‐Late Weichselian deposits in the Suupohja area, western Finland

“…2), it is suggested that the glacifluvial deposits at the base of the sections at Risåsen belong to the Harrinkangas Formation and are of Saalian age, as has also generally been accepted by previous workers (e.g. This corresponds to the observations reported by Kujansuu et al (1991), Kujansuu (1992) and Pitkäranta (2009b). The pollen taxa in the palaeosol horizon (Ostrobothnia Geosol) overlying the Harrinkangas Formation at Risåsen indicate that it was formed during a time when the area was forested, and the climate was at least partly as warm as or warmer than today.…”

“…2) occupy the same lithostratigraphical position as the Kodesjärvi Formation, described by Pitkäranta (2009b) at Penttilänkangas, 20 km to the SSE from Kiviharju. 2) occupy the same lithostratigraphical position as the Kodesjärvi Formation, described by Pitkäranta (2009b) at Penttilänkangas, 20 km to the SSE from Kiviharju.…”

“…3), the fine sand unit is covered by a 3-m-thick talus where no observations could be made. This cross-bedded sand unit is very well sorted and interpreted here as aeolian in origin, and it is possibly a lithostratigraphical equivalent of the Isojoki Sand (Pitkäranta 2009b) (Fig. 3).…”

The interglacial–glacial cycle and geochemical evolution of Canadian and Fennoscandian Shield groundwaters

“…Peltier, 1994;Kleman and Hättestrand, 1999). Although permafrost features occur only sporadically, permafrost can be considered similarly forming in front of advancing and retreating glaciers (Saarnisto, 1977;Kukkonen and Š afanda, 2001;Kukkonen and Jõ eleht, 2003;Pitkäranta, 2009).…”

Late Cenozoic deep weathering patterns on the Fennoscandian shield in northern Finland: A window on ice sheet bed conditions at the onset of Northern Hemisphere glaciation

“…The figures for ice cover duration are probably overestimates, however, as temperatures close to those in interglacials were reached in early and middle Weichselian interstadials in central and eastern Finnish Lapland (Helmens et al, 2000;Mäkinen, 2005;Väliranta et al, 2009;Sarala et al, 2010;Sarala and Eskola, 2011;Salonen et al, 2014;Lunkka et al, 2015). Palaeoenvironmental proxies indicate that cirque glaciation in the mountains was accompanied by cool interstadial conditions on the shield lowlands (Helmens et al, 2000) and that mountaincentred ice sheets were accompanied by widespread permafrost in Finland (Pitkäranta, 2009b). These broad estimates indicate that ice sheet cover in the ice divide zone was relatively brief and largely confined to the middle and late Pleistocene, that permafrost may have developed for a total period of N 1 My and that interglacial-interstadial conditions may also have prevailed for N1 My in the Early and Middle Pleistocene on the shield lowlands of northern Finland.…”