Study of Unio shells in the Quaternary deposits, southern Iraq

Abstract

Shells are useful in evolutionary biology and paleobiology. Freshwater shells compose the main types of mollusks, and can use as a key for ecological variations. Shell samples in the present study were collected on the highway of Nasyriah city-Samawa city, southern Iraq. The study area contains a large accumulation of shells at 6-7m depths, especially at 7m depth. The main types of these shells are Unio, Corbicula, and Melanoides tuberculata. Unio was the most species common in the study area. Unio species were used to detect the paleoenvironment in Quaternary deposits, in southern Iraq. Calcite and aragonite are the common minerals in the Unio shells. According to the distribution and percentage of calcite and aragonite in the Unio shells, it was found the calcite at 6m is more than 7m, whereas the aragonite at 7m is highest compared to 6m. Under X-Ray Fluorescence analyzers, found that calcium oxide, silica, magnesium oxide, and phosphor oxide are the major oxides in the Unio shells, while Zn, Sr, Pb, and Rb are the main trace elements. Strontium (Sr) has a high concentration in the Unio shells at 7m than 6m, while magnesium (Mg) is found in a high concentration at 6m than 7m. According to trace and some of the major elements concentrations, the paleotemperature, paleosalinity, and water contamination of rivers at 6m are more than 7m, and the river water at 7m depth was fresh water with a high abundance of nutrients and climate was suitable to growth mollusks shells like Unio shells.