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[1] We report an analysis of geothermal heat flow density (HFD) in the Fennoscandian Shield and East European Platform showing a systematic variation with depth. The HFD data (1352 values) averaged in 25 m depth intervals and in 1°Â 2°latitude-longitude areas increase from $35-40 mW m À2 in the first 500 m to $45 mW m À2 at 1000 m, finally reaching $50 mW m À2 between 1000 and 3000 m and deeper. We attribute this variation to long-term climatic changes in ground surface temperatures (GST) during the Weichselian (late Pleistocene) glaciation and the Holocene. Monte Carlo inversion was applied for determining ground surface temperature histories during the past 100,000 years, and the results indicate the lowest GST at time of the Last Glacial Maximum ($20,000 years B.P.), followed by an average warming of 8.0 ± 4.5°at $10,000 years B.P.

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Abstract-The estimates of the age of the Kaali impact structure

The current case study presents results of the ground-penetrating radar (GPR) profiling at one of the Saadjärve drumlin field interstitial troughs, the Rahivere bog, eastern Estonia. The study was conducted in order to identify the bog morphology, and the thickness and geometry of the peat body. The method was also used to describe the applicability of GPR in the evaluation of the peat deposit reserve as the Rahivere bog belongs among the officially registered peat reserves. Fourteen GPR profiles, ~ 100 m apart and oriented perpendicular to the long axis of the depression, covering the bog and its surrounding areas, were acquired. In order to verify the radar image interpretation as well as to evaluate the velocity of electromagnetic waves in peat, a common source configuration was utilized and thirteen boreholes were drilled on the GPR profiles. A mean value of 0.036 m ns–1 corresponding to relative dielectric permittivity of 69.7 was used for the time–depth conversion. Radar images reveal major reflection from the peat–soil interface up to a depth of about 4 m, whereas drillings showed a maximum thickness of 4.5 m of peat. Minor reflections appear from the upper peat and mineral soil. According to the borehole data, undecomposed peat is underlain by decomposed one, but identifying them by GPR is complicated. Mineral soil consists of glaciolimnic silty sand in the peripheral areas of the trough, overlain by limnic clay in the central part. The calculated peat volumes (1 200 000 m3) were found to exceed the earlier estimation (979 000 m3) that was based solely on drilling data. Ground-penetrating radar, as a method that allows mapping horizontal continuity of the sub-peat interface in a non-destructive way, was found to provide detailed information for evaluating peat depth and extent