Provenance and tectonic setting of the Upper Red sandstones in south of the Saveh area

Petrographic studies and modal analysis were carried out on the Upper Red sandstones in south of the Saveh area to determine their tectonic setting, provenances, weathering and paleoclimate conditions. The Upper Red Formation with Miocene age has been deposited on the Qom Formation with a conformable and distinct boundary and covered by Pliocene conglomerate with an angular unconformity. This formation contains an alternation of sandstone, conglomerate and red mudstone. Microscopic studies show that the grains are generally sub-angular to angular, and sandstones are poorly to moderate sorted. The calcareous cements filled the pores between grains. The main components of these sandstones are Q11F29L60 in average. The most lithic grains are volcanic fragments with intermediate to basic compositions. Other lithic grains including low-grade metamorphic (slate and phyllite) and carbonate grains. Plagioclase is more than the Kfeldspar. Quartz grains are more monocrystalline with undulose extinction. Modal analysis of Upper Red sandstone indicates that their compositions are mainly feldspathic volcanic arenite according to the Folk classification. Textural and mineralogical maturities of the sandstones display these sediments have been influenced by slight chemical weathering and have been transported in a relatively short distance from parent rocks. Plotting the point counting results on the QtFL and QmFL Dickinson diagrams indicated that the Upper Red sandstones may be derived from volcanic rocks which exposed by uplifting of the Urmia-Dokhtar Magmatic Arc. In addition, the log Qt/F+RF versus log Qp/F+RF diagram indicate the paleoclimate condition was arid. The calcareous cement and red color of these sediments supported this condition.