STRATIGRAPHY OF THE HIGH FOLDED ZONE
The stratigraphy of the High Folded Zone (HFZ), in Iraq is reviewed. The oldest exposed rocks are Early Triassic in age, whereas the youngest are of Pliocene – Pleistocene age, which belong to the Bai Hassan Formation. The exposed stratigraphical column is represented by 36 formations, with 10 main types of Quaternary sediments, which have wide geographic extent and well preserved in the HFZ.
The Triassic, Jurassic, Cretaceous and Paleogene rocks are mainly of marine carbonates with some clastics. The Oligocene rocks form a complex of reef – backreef – forereef and are restricted almost in the eastern and western parts of the area, with restricted exposures in different parts. The Early and Middle Miocene rocks are mainly of marine origin, lagoonal carbonates and fairly developed evaporates, respectively, with restricted exposures. The Late Miocene – Pleistocene rocks, which represent the beginning of the continental environment, consist of molasse sediments, deposited in sinking foredeep, which had few separated and isolated basins. The Quaternary sediments are well developed, especially Pleistocene river terraces of different stages, alluvial fan sediments, calcrete and other different types. Glacier moraine sediments, may be present in Rawandooz – Galala vicinity.
For each exposed formation, the type locality, exposure areas, subsurface extension, main lithology (as described in form of members and/ or informal units), thickness, fossils, age, depositional environment, and the lower contact are described. The described lithologies of the formations by different authors from different localities are reviewed, with occasional remarks by the present authors. The main tectonic events and the paleogeography of each era or period are reviewed briefly. Each formation is discussed, for the majority of them the present authors' opinion are given, with many recommendations for future studies. Some new ideas dealing with many aspects for many formations including proposals for establishing new formations are given, too.