Using sedimentological analyses of granulometric composition, calcimetry and macropaleontological analysis of biogenous material residues in the MIR1 core of the Mirna River delta plain the reconstruction of the past relative sea levels, depositional facies in the Mirna River and the geomorphological and environmental evolution was attempted. This thesis also examines the precision and accuracy of field methods by comparing them with the exact results of laboratory analysis. The area of the Mirna River valley is structurally part of the External Dinarides which are dominated by limestones deposited on the Adriatic-Dinaric carbonate platform in the time range from Cretaceous to the Eocene. After the Holocene trangression sea level reached upstream in the Mirna River valley for a few kilometers further than the recent coastal line does. In the last 7,000 to 6,000 years, the Mirna River intra-estuarine delta has prograded into the Adriatic Sea. The sediment core MIR1 contains records of these changes in the environment since each depositional environment contains characteristic fossil assemblages and sedimentary characteristics that reflect the living conditions and sedimentation conditions of the material as the river progressed over time. Human activity has been continuously increasing and furthering the evolution of Mirna River valley and the estuarine (bay-head) delta and the river banks since it began 6000 years ago BC when the first settlers arrived in the area.