نقش بررسي هاي كاني شناسي و شاخصهاي آماري رسوبات در منشاءيابي تپه ماسه اي شندان سراوان بلوچستان

The Role of Mineralogical and Statistical Analyses of Sediments In Source Studies of Shandan-Saravan Sand Dunes, Baloochestan

Samples taken from lithological units and sand dunes in point grid, were analyzed through morphoscopic and mineralogical studies. The same-sized maps of sand dunes were then drawn by using statistical parameters of grains. Maps and distribution of statistical parameters show that grain size decreases from 0.37 mm in west to 0.18 mm in east through Erg. Also there is an increase in the degree of sorting and roundness in this direction. The coarsest particles are found in ripple marks as well as in sand sheets whereas nebkas contain the finest ones. According to the relationship between grain size and their transportation distances by winds, the first accumulation phase (D1) is 3 km far from the erg. Based on microscopical results, rock fragments make up 85%, whereas minerals make up 15% of grains including quartz, feldspar and calcite. According to X-ray diffraction and Electron Microscope Scanning, quartz frequency relates to quartzose-sandstones, calcite frequency is related to flishe limestene with clay minerals haveing originated from shale sources. In the second sedimentation phase (D2) or erg, 98.54% of sands have been transported through saltation, while only 1.2 %, and. 0.26% through suspension and creep processes respectively. According to morphscopic analyses by using binocular and SEM photos of quartz and results from Friedmanʹs Diagram, 80% of sands were shown to be transported by collaboration of water and wind, while only 20% by water alone. This indicats that water is an important agent in semi-arid bioclimatical zones. Finally, based on mineralogical studies, the most important sources of Shandan sand dunes are recognized as Saravan lithological units (ES^3, ES^4) as well as Zaboli lithological unit (EZ) with other units having little effect in sand production for the erg.