Correlation of Lithuanian Maritime Pleistocene tills based on their mineralogy

Jurgita Paškauskaitė, Petras Šinkūnas — Thu, 05 Mar 2015 00:00:00 +0200

The previous studies of Pleistocene deposit in the Lithuanian Maritime Region (LMR) show the difficulty of its stratigraphical subdivision and correlation of sediment beds. Due to scarcity of biostratigrafical and absolute dating results, the variety of litostratigraphical criterions such as till petrography, geochemistry or even well rounded hornblende grain amount and other physical or visual characteristics used for litostratigraphy and correlation of tills did not give effective results. The article provides correlation of Pleistocene deposits based on mineralogical composition of the sandy fraction of tills from one geological profile located along the Lithuanian Baltic Sea coast using the multivariate statistics. The mineralogical data from six boreholes were statistically analysed and lithostratigraphical interpretation was made. Data analysis displayed that the till complexes have different amount of minerals from statistically derived mineral associations. It allowed distinguishing of six till complexes characterized by distinct mineralogical composition. These differences are clearly visible in the results of the statistical comparative analysis of the mineral composition of adjacent tills complexes. The stratigraphical identification of distinguished till complexes is based on its occurrence, inter-till deposit absolute dating and interglacial sediment palaeobotanical results.

Seasonal variations of radon concentration in soil air in different geological conditions on the example of Estonia

Krista Jüriado, Valter Petersell, Anto Raukas — Thu, 05 Mar 2015 00:00:00 +0200

Radon risk in Estonia is among the highest in Europe, influencing human health in many areas. The measured radon level in soil air differs considerably between spring– summer and autumn–winter periods at the same measuring point. Such variations are an obvious obstacle in interpreting reliably the radon risk level in the soil. To tackle with this problem, a monitoring system was established. Radon (²²²Rn) concentrations in soil air were investigated in four geologically different sites at three depths during three years every 26–40 days. The results showed that at every site the concentration of radon in soil air depended on the eU (²³⁸U) concentration in Quaternary deposits and underlying bedrock, on rock types, as well as on aeration circumstances during measuring, such as temperature, topsoil aeration, precipitation and air pressure. The measured radon level concentration starts to increase in autumn when the topsoil turns wet, air humidity increases and ground begins to freeze. It reached the maximum in late winter, when the ground is most frozen. The radon concentration is at its lowest during the warm and dry summer period when topsoil aeration and radon permeability are at their maximum.

Geologija

Correlation of Lithuanian Maritime Pleistocene tills based on their mineralogy

Seasonal variations of radon concentration in soil air in different geological conditions on the example of Estonia