برخاستگاه ماسه سنگ های سازند شیر گشت به سن اردویسین فوقانی در جنوب غرب کاشمر بر اساس مطالعات پتروگرافی

Upper Ordovician sandstones of Shirgesht formation in Boghoo mountain section was studied for petrography and provenance determination. The 50 m thick siliciclastic interval is located in SW Kashmar in Khorasan Razavi province. 14 thin sections were analyzed for grain counting of the major components of quartz, feldspars and lithoclasts. Abundance of Quartz is around 75% to 85%, feldspars are 15% to 18% and lithoclasts are 1% to 5% in the sandstones. Minor components include muscovite, zircon and tourmaline with average grain size of 0.06 to 0.1 mm in diameter. The studied samples are classified in very fine sandstone class, and immature, which arenamed as Arkosic wacke. For the provenance, studied sandstones have plutonic sources, which have originated in a stable cration oftectonic system.