Maturity Index and the Origin of the Source Rocks of Sandstones for Injana Formation in Aqra Region, Northern Iraq

Abstract

The present study deals with the sandstones components of Injana Formation (Late Miocene) in Aqra area, northern Iraq. The Injana Formation consists of cyclic repetition of sandstones and claystones beds. Nineteen samples from sandstone beds were chosen for point counting and petrographic studies. The classification of these sandstone beds are feldspathic litharenite. Petrographic study shows that the sandstones consist of mono and polycrystalline quartz, K- Na feldspar, carbonate and other sedimentary rock fragments, igneous and metamorphic rock fragments and calcite cement. In addition fine- grained clay matrix. The study marked mineralogical immature and physically submature sandstones. These sediments were deposited under (semi arid-semi humid) climatic conditions. The origin of these sandstones were recycled orogen and dissected arc – transition arc of the collision zone between the passive Arabian plate and the active Turkish-Iranian plates. These events lead to sedimentary - tectonic intermeshing of the rocks on both plates which were uplifted as high terrains of igneous, sedimentary and metamorphic rocks, which are the source of Injana Formation sandstones.