The geochemical analysis of biogenic sediments was used to reconstruct environmental conditions and the impact of human activity from a small mire geo-system in the Sandomierz Basin (Poland SE). Changes in the nature of selected geochemical indicators show a significant impact on the transformation of the mire during the early stages of human activity. It is reflected in the geochemical record by means of a high proportion of heavy metals – cadmium, lead and copper. Evident variability of main geochemical components concentration is also visible in a vertical record of analysed cores. This is a consequence of the sedimentary basin asymmetric configuration and the ensuing variable biogenic sedimentary succession.