Determination of sedimentation rate of Hoor-Al-Azim wetland by carbon-14 method and analysis of its past climate using element geochemistry

Abstract

Wetland sediments are considered as prominent documents for studying climate change and sedimentary environments globally. Environmental changes (whether in climate, terrain, or in both) affect the process of sedimentation. The sediment changes are also reflected in the physical and chemical properties of sediments through which the process and the environment of sedimentation in the ancient times can be tracked. There are several methods for identifying climatic conditions in the past, such as isotopic studies, vegetation identification, sedimentology, and geochemistry of elements. In this research, after the registration of the sediments, to reconstruct the past climatic conditions of the Hoor-Al-Azim wetland, the changes in manganese, calcium, iron, and aluminum elements along with three sedimentary cores at three stations were studied, and age determination with carbon-14 isotope in Core 3 was applied to determine the sedimentation rate. The depth of the cores taken was 50 cm and the number of specimens in each core was 11; a total of 132 samples were sent to the steel company of Khuzestan, so that the concentration of metals could be measured by ICP-OES. To determine the age of the 15, 30, and 45 cm depths taken from the southernmost core, sediment samples were sent to the Poznan Radiocarbon Laboratory in Poland. The average sedimentation rate in Hoor-Al-Azim wetland is around 0.3 mm per year and the core covers about 1500 years. As calcium, manganese, iron, and aluminum are the important indicators for determining the chronic climatic conditions and are sensitive to the climatic changes, and due to the anomalies of these elements along the cores, about 700 years ago, with decreasing calcium and elevated iron, alumina and manganese elements are the wet climates that have led to the introduction of continental cessation deposits into the basin. After this period, the increase in calcium levels, which indicates an increase in sediment in the basin is considered as the beginning period of dry climate in the region. Of course, the effects of the changes of Karkheh River and the impact of human factors on these changes should not be neglected.