Geophysical investigations of Pallas-Yllästunturi region using GPR and seismic refraction

Abstract

This thesis investigates the subsurface geology of the Pallas-Yllästunturi region using Ground Penetrating Radar (GPR) and seismic refraction to enhance geological information regarding the area, particularly in peatlands. The primary objective is to delineate key lithological boundaries, including peat, glaciofluvial sediments, till, and bedrock, to support future hydrological and hydrogeological studies. The study integrates GPR data with a radar frequency of 50 MHz and 100 MHz along with limited seismic refraction surveys to improve depth estimations and validate subsurface interpretations. GPR proved highly effective in detecting the peat-to-mineral interface and identifying bedrock where signal penetration was sufficient, while seismic refraction provided critical depth validation and constraints particularly for the bedrock. Spatial depth maps were made particularly for peat deposits and bedrock. The peat depth was shown using a class interval of 0.5 meters with a range from 0-8.5 meters. The bedrock depth was shown using a variable class interval with a range from 2-24 meters. Glaciofluvial deposits are also represented on a map to aid future hydro(geo)logy studies. The results contribute to a better understanding of sediment distribution in the Pallas region, offering insights for future studies into hydro(geo)logy, groundwater flow and peatland dynamics. Future work should incorporate additional geophysical techniques, such as Electrical Resistivity Tomography (ERT), in order to further refine the interpretation.