Marl units classified of Zanjan province based on physiochemical characteristics and Cluster analysis

Marly units cover about 4438 square kilometers (20% of the total area) of Zanjan Province territory. The research shows that various scholars, although sporadically, have considered a relationship between physicochemical factors and the classification of Marl. In this paper, the classification of Marls in Zanjan Province has been investigated based on physicochemical properties and cluster analysis.

To conduct this research, 18 studied units have been defined by grouping and combining the slope, climate and Marl units of geological formations in ArcGIS9.3 software environment. In addition, 120 samples were taken from two depths of 0-10 and 0-30 cm. The data obtained from physicochemical analyzes were analyzed using SPSS statistical program.

According to the results, Marl units of Zanjan province, are divided into two groups based on their physicochemical characteristics: evaporative or non-marine such as Pliocene, upper red, lower red, and Eocene Marl, and non-evaporative or marine such as Qom and Cretaceous Marl.These marl units are part of normal formations in the surface layers while in the deep layers the situation is different, the salinity and alkalinity of some of these units such as Pliocene and Qom marl units increases. But other units, despite the increase in depth according to the chemical analysis performed at a depth of 0-30 cm, are still in normal category in terms of salinity and alkalinity. According to cluster analysis, 6 variables including clay, sand, PI, cation exchange capacity (CEC), the amount of dissolved sodium (Nasol) and sulfate (So4) were situated in the center of the classification. This shows their importance in the separation and grouping of marl units. Therefore, it can be concluded that these 6 variables can be effective and useful in classification of marl units in Zanjan province.

Investigation of differences and changes in physicochemical properties of marl units at depths of 0-10 and 0-30 cm by t-test show that the units at the two mentioned depths have a high correlation coefficient in most physical, mechanical and chemical variables. Also, they show significant differences in some variables as silt, cation exchange capacity (CEC), percentage of organic carbon, the total neutralizing value (TNV) of the limestone, the amount of dissolved sodium (NaSol), sodium absorption ratio (SAR), Chloride (Cl), sulfate (SO4) and the liquid limit (LL). Therefore, according to these physicochemical properties, it is possible to classify and group Marls in Zanjan Province.Investigation of the effect of physicochemical variables on the separation of marl units using F-test and comparison of means for different units by Duncan test confirmed the feasibility of separation and grouping of marl units based on physicochemical variables. They can be classified at least in one group based on the electrical conductivity or at most in three groups according to effective variables such as silt, sand, lime percentage, sodium absorption ratio and liquid limit and plasticity index.Based on the cluster analysis, 6 variables of the amount of clay, sand, and the plasticity index (PI), cation exchange capacity (CEC), dissolved sodium (NaSol) and sulfate (So4) are vital in the classification and indicate importance in separation and grouping of Marl units. Therefore, it can be said that these 6 variables can be effective and useful in providing a classification of marl units in Zanjan Province.