Environmental Changes of Karkheh River Delta Using Sediments Geochemical data

Deltas are the most important morphological units which have a tremendous effect on agricultural activities, mining, coastal management, etc. Despite appropriate soil and water resources, deltas are influenced by environmental phenomena such as climate change and sea level changes. The effect of these changes will appear on physico-chemical and mineralogical features of delta’s sediments. The current research was conducted to analyze Karkheh delta depositional environments based on the chemical characteristics of ancient sediments. Depositional environments and locations of core were identified using digital data processing, geomorphology mapping, and ​​ initial visit of the area. The coring was carried out using rotary drilling machine continuously down to a depth of 10 m in Jofeir and Rofayeh. Twenty samples were collected from cores for mineralogical and chemical tests. The changes in chemical and mineralogical characteristics revealed that at least three major discontinuities exist between sedimentary layers to a depth of 10 m. In addition, thickness and type of the sediment are not in the same and change depending on the stability of depositional environments. The increasing trend in Mg/Ca, magnesium and salinity; and the decreasing trend in clay particle percentage show that sedimentary environments tend to change toward a dry conditions and high energy environments from depth of 5 to 10 meters. In contrast, at the depth of 5 to 4 and 3 to 0 meter, this trend is towards more humid climate and low energy environments. Therefore, it is concluded that the depositional environment of Karkheh River delta at the upper Holocene is not constant, and this led to recognizable changes in the delta.