Research concerning changes or chosen chemical elements concentration in alluvial sediments was conducted in the lower course or the Obra river valley. The analyses of Fe, Mn, Cu, Zn, Ca, Mg and K concentration were done in a fragment or vertical profile, which was characterized by variable lithology. On the basis of statistical analysis (cluster analysis) an attempt was made to distinguish geochemical groups of alluvial sediments of the Obra river valley. Six geochemical groups, which represent reductive conditions within peat deposits, the environment ofllood sediments (inserts of fine sands within peats and sandy silts in the top of the profile) and the environment or river bed sediments (fine sands in the bottom part ofthe profile), were singled out. Results of the study show that it is possible to distinguish the above mentioned depositional environments on the basis of variations of sediments' chemical constitution.