Resumen de Procedencia de las areniscas de la unidad superior de la Fm. Fortuna en el NE de Túnez
The Fortuna formation outcrops in central, eastern and north-eastern Tunisia and is composed by detritic series of fluvio-deltaic origin that can be divided in three units. The lower (Upper Oligocene) and middle (Lower Miocene) units were deposited in deltaic-lagoonal environment, while the upper unit (Aguitanian) consist of medium to coarse-guartz-rich sands deposited in braided fluvial system. In northeast Tunisia, sandstones of this upper unit can be classified as guartz-arenites, texturally mature (good roundness, sphericity and sorting), and containing scarce rock fragments and feldspars.
Provenance of the Fortuna sandstone was from the SV\J (Sahara Platform). The source area was characterized by guartz-cemented arenites (Palaeozoic Tassilis sandstone, Cretaceous "continental intercalaire" and Eocene sandstone) and by plutonic and metamorphic rocks (probably from Floggar basement massif). Recycling is an important fact to explain high quartz contents in Fortuna sandstone as proven by the presence of inherited overgrowths, but this process together with transport, can not fully explain their extreme maturity. The source area was probably affected by an alteration mantle (saprolite) that fed the Miocene fluvial network, or arrived indirectly from recycling of the pre-Miocene sedimentary rocks.
