Grain size and mineralogical studies of sandy sediments in southwestern Iran

The objectives of this study were to determine the nature (aeolian vs. alluvial) and origin of sandy sediments in southwestern Iran (Khuzestan province) were collected in two transects across (NW-SE directions) and perpendicular to the Karkheh River, by using grain sized distribution characteristics, and the mineralogy and micro-texture of quartz grains of forty-five surface samples (0-30cm) at interval distances of ~1.5km. Standard sieves (0.5phi-intervals) were used for determining sand fractions. Silt and clay fractions were measured using the pipette method. Mineralogical composition and surface micro-texture of quartz grains of the selected samples were examined using a polarizing microscope and a scanning electron microscope, respectively. Mz (mean grain size) varied between 1.82 to 4.56f. The variations of Mz indicated the directional particle size fining the NW-SE transect. Sorting (dI) was 0.46 to 2f and with an average of 0.97f was poorly to well sorted. [FE1] The mean value of skewness (SKI) was 0.12 which ranged from -0.24 to 0.46 and skewed to fine particles. Kurtosis with mean values of 1.21 varied between 0.85 to 2.25, which indicated a slight leptokurtic. Grain size characteristics showed a disturbance near the river due to the fluvial processes. Quartz grains were rounded and evidences of both aeolian and fluvial processes were observed on the grains’ micro-texture. The mineralogy of sediments were similar to those in Saudi Arabia. This mineralogical similarity, as well as prevailing wind direction and grain size variations, indicates the possibility of the sediments to have likely originated from the Arabian plate.