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

• Main Author: Reijo Pitkäranta
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Corresponding author; Ice; Ice Sheet; permafrost
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.495.1419; http://www.geologinenseura.fi/bulletin/Volume81/Pitkaranta_2009.pdf

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 pro-file 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 ob-servable 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 prop-erties (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 sim-ilar 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 pos-sibly 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.