Iraqi Bulletin of Geology and Mining

The geomorphology of the Iraqi High Folded Zone (HFZ) is reviewed in the present article. The High Folded Zone is characterized mainly by mountainous topographic nature. The nature of the topography reflects the type of the exposed rocks and the structural effect. Generally, two main different topographical parts could be recognized, this is attributed to the presence of longitudinal and narrow anticlines and shallow synclines, locally faulted. Moreover, the surface of the HFZ area is dissected by complicated drainage patterns with variable density; they drain the area towards the main streams and rivers, and then toward the Tigris, Greater Zab, Lower Zab and Sirwan rivers. The chemical and mechanical weathering are active, the water is the main erosional agent being also an active process.
A generalized geomorphologic map of the HFZ is compiled, at scale of 1: 1000 000. The map elucidates the spatial distribution of the main geomorphologic units and the related morphologic features. The geomorphologic units are classified genetically into six classes, which include different landforms. The recognized genetic units are: Structural – Denudational, Denudational, Fluvial, Solution, and Man-made origins, and possible Glacial moraine. Each of these units includes different lithomorphologic landforms, which were developed due to weathering, erosion and depositional processes, in conjunction with tectonic, structural, lithological, and climatic factors.
The present study revealed that the geomorphologic evolution of the HFZ was greatly influenced by the last phase of intensive orogenic movement that took place during Late Miocene – Pliocene, and continued during the Quaternary Period with less intensity. During the Quaternary Period, the climate became a leading factor in controlling the majority of geomorphologic processes, particularly the fluvial. The Quaternary long-term climatic changes are deduced by well-developed river terrace stages along the main rivers and their tributaries, and some large streams and valleys, beside numerous alluvial fans and calcrete.

The High Folded Zone is an integral part of the Western Zagros Fold – Thrust Belt of Iraq. It is characterized by the presence of a huge number of NW – SE and E – W trending, high amplitude, short wavelength southwest and south vergent folds. The landforms in the zone are highly structural and reflected on the topography as high rugged anticlinal mountains separated by deep narrow synclinal valleys.

The Folds display wide range of geometries and sizes, reflecting that more than one folding mechanism is possibly responsible for their initiation and development. Judging by their style and geometry, simple buckle folds, generated by flexural-slip and neutral-surface folding mechanisms, as well as fault-propagation folds appear to dominate fold types in the zone.

Significant topographic and structural relief is clearly observed across the boundary between the High Folded and Low Folded zones of the belt. This structural uplift is attributed to the involvement of the basement by thrust faulting beneath the sedimentary cover, and the deformation is considered to be a "thick skin" type in the 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.

The Hydrogeology of the High Folded Zone, in Iraq is reviewed. This zone is characterized by rugged topography, and presence of deep canyons and narrow valleys with well defined mountainous topography. The oldest exposed rocks are Early Triassic in age, whereas the youngest are of Pliocene – Pleistocene age, which belong to the Bai Hassan Formation, in addition to Quaternary Sediments.
The High Folded Zone can be divided into five major hydrogeological basins, which are: Zakho, NW Barzany, Central Harir, Central Dokan and Sharazoor Basins. And these basins are subdivided into ten sub-basins. Two main groups of carbonate aquifers are described based on geological and hydrogeological characteristics; these are: Bekhme Karst Aquifers (Qamchuqa, Dokan and Kometan formations) and Pila Spi Fractured Karst Aquifers (Sinjar, Khurmala and Avanah formations). In addition to these important carbonate aquifer complexes, some clastic units, such as Quaternary Sediments, Bai Hassan, Mukdadiya, Injana, Fatha, Kolosh and Tanjero formations are sufficiently permeable to form local aquifers.
The source of recharge water within the High Folded Zone is mainly from direct precipitation and snow melt during summer at the highest elevated areas of the zone, and from the Suture and Thrust Zone at the northeast. The Low Folded Zone represents the discharge zone to the area, beside wells and springs. The general trend of the groundwater movement at this area is mainly from north and northeast towards south and southwest, with local different directions due to topographic and structural characteristics of the area. There is a hydraulic continuity between water bearing formations within this zone, depending on the piezometric relations of the water-bearing layers throughout the area.
The depth of the groundwater increases at the high lands and at the flanks of the synclines, and decreases at the central parts of the basins and at the discharge areas. The transmissivity of aquifers often increases at the central parts of the synclines and along river courses, and within the alluvial fans, as more permeable sediments are available.
The salinity of the groundwater is characterized by low values; with the prevailing type of fresh water being Ca (Mg)-HCO3, with increasing magnesium content in dolomites. This salinity and chemical composition of groundwater changes in the presence of gypsum, anhydrite and halite in the Fatha Formation, which is sometimes present in the S and SW parts of the Zone. The hydraulic conditions and chemistry of aquifers within the High Folded Zone are closely linked to the stratigraphic, lithologic, structural and topographic characteristics of the water bearing formations. According to the hydrogeological evaluation of the High Folded Zone, it can be considered as promising zone for groundwater development in Iraq.

The High Folded Zone is one the main Metallogenic Zones in Iraq; it is rich in non- metallic deposits and industrial rocks. All the mineral deposits in this zone are sedimentary in origin including marine and continental sediments. They range in age from Triassic to Pleistocene, occurring mostly as bedded thick sedimentary strata deposits. Previous work in the area indicates that all of these economic deposits are building raw materials such as limestone, gypsum, clays, sand, gravels and orthomarble. The formation of the mineral deposits and industrial rocks in the High Folded Zone was controlled by paleogeographic, tectonic and structural factors.

This study gives the type, location, specification, reserves of the main mineral, industrial rock deposits, and their chemical composition. These mineral deposits provide a very promising potential for future development of the region.