Geodiversity in the Iraqi Western Desert. A Critical Discussion

The Iraqi Western Desert (IWD) is characterized by enormous geodiversity types in different geological aspects; including geomorphology, lithology, structural geology, mineral deposits, karst forms, and geological hazards. Within each of the mentioned aspects, different forms of different shapes, sizes, and origins can be seen in different parts of the IWD, which we divided into 4 parts, among them 11 main types and 25 sub-types. We have studied geological maps of different scales (1:100000 and 1:250000), interpreted satellite images, and reviewed tens of published articles, books, and scientific reports, besides field visits which lasted for tens of years to conduct the current research. Tens of examples are presented, which confirm geological Geodiversity in the IWD including many field photos and satellite images, as best available. We also presented a satellite image of the IWD and marked 54 locations of different types of geodiversity including ex-situ and in-situ. Locally, detailed explanations are given for some significant forms and/ or features to present their types, origins, and modes of development.


Introduction
Many researchers have defined geodiversity as the variety of earth materials, forms, materials, and processes that constitute and shape the Earth, either the whole or a specific part of it.Relevant materials include minerals, rocks, sediments, fossils, soils, and water [7,24,4].Geodiversity is not homogeneously distributed and studied on our planet.The recognition of geodiversity may be indicative not simply of the distribution of geodiversity but also of the status of geoconservation initiatives.In this regard, it is worth mentioning that the biodiversity of an ecosystem stems at least in part from its underlying geology [14].Geodiversity also forms a significant part of developing nature-based solutions to challenge the global environment and requirements for natural resources [16].There is no evidence, from reading these definitions, that any aspect of Earth's heritage is deliberately excluded from geodiversity.According to [15], all definitions differ from one to the other, but what they appear to have in common is a desire to be very inclusive in what they define as 'geodiversity'.A general definition of Geodiversity can be accepted as "Geodiversity is the variety of rocks, minerals, fossils, landforms, sediments, and soils, together with the natural processes which form and alter them".
Generally, studies concerning Geodiversity in Iraq are very rare; however, we found few articles that dealt with this subject.Mohammed and Al-Zubaidy [11] conducted a study about Geodiversity in the Ga'ara Depression in the Iraqi Western Desert and concluded that "An intrinsic relationship between geological and biological diversity was found at Ga´ara Depression, in the Iraqi Western Desert".Sissakian et al. [21] studied tens of isolated hills in different parts of Iraq including the Western Desert.They described different forms and shapes with lithological diversity.Mohammed and Al-Zubaidy [12] conducted a study, that dealt with the Geodiversity of vertebrates near Razzazza Lake on the eastern margin of the Iraqi Western Desert.They concluded that there is a positive relationship between lithology and living vertebrates.Sissakian et al. [22] studied the Ga'ara Depression, which is located in the central part of the Iraqi Western Desert.They recognized different geomorphological, lithological, and mineralogical diversities.Sissakian and Fayedh [20] studied the geological hazards in Al-Anbar Governorate and mentioned about the sinkholes.Sissakian et al. [23] studied the sinkholes in the Haditha vicinity and presented statistical data about the types, sizes, and shapes of 58 studied sinkholes.Hussain [9] studied the Geodiversity of the Smaquli area in the northern part of Iraq (Kurdistan Region) as a potential geopark in the Kurdistan Region of Iraq.She determined elements of geodiversity in the Smaquli area and evaluated and used them as geoconservation through potential geopark.Khalaf et al. [10] conducted research in the Northeast of the Missan area, the southeastern part of Iraq dealing with Geosite locations, and concluded that several geological and geomorphological features were used to define and locate Geosites.The Iraqi Western Desert (IWD) occupies the western part of Iraq (Fig. 1), forming the majority of AlAnbar Governorate with Ramadi city as the capital of the governorate, and the coverage area is about 104000 km 2 .Due to this large area, different geological phenomena, forms and features are developed due to different reasons and environments.The current research aims to indicate Geodiversity in the IWD as represented by different geological aspects (elements).The main involved geodiversity elements are presented in Table (1).

Materials and Methods
We reviewed the available data about the Geodiversity in the IWD, including different geological data, maps at different scales, satellite images, geological reports, and published scientific articles.Besides, our field visits through the last four decades during geological mapping, engineering geological mapping, and following-up postgraduate students.To facilitate the description of the Geodiversity in the IWD, we divided the area into four parts (Fig. 1), and the described aspects of Geodiversity are compared between those four parts (Table 1).We prepared a location map using Google Erath image (Fig. 1), which shows the four parts (A, B, C, and D, Fig. 1), besides 1) Main valleys, 2) Well known isolated hills of different shapes and local terms (Table 1), 3) Main shallow depressions (Faiydhat), 4) Two well-known sinkholes, 5) Two dams (Haditha and Hauran) and other three small dams, 6) Bitumen seepages, 7) Two "Tars" (Tar is a local name for long cliff), Tar Al-Sayed and Tar Al-Najaf (Fig. 1), 8) Main quarries, 9) Springs, 10) Petroglyph and artifacts, and 11) Main geographic locations.We recognized and distinguished 27 different geological aspects (Subtypes) in the IWD, which represent Geodiversity, they belong to 10 main Geodiversity types (Table 1).Each of the 27 geological aspects is described separately explaining its Geodiversity at each of the four divided parts in the IWD.Field photos are presented when are available for any of the described types indicating the location and brief description.Locally, satellite images are also presented for some described Geodiversity sites, when it appears clearly and the size of the site permits its appearance in the satellite image.

Geodiversity
The recognized and identified types of Geodiversity in IWD (Table 1) are described hereinafter systematically.

Geomorphological Types
Within this type, we recognized five sub-types (Table 1), these are described in detail, hereinafter.
3.1.1.Sinkholes.Sinkholes are well-known karst forms, which are developed in carbonate rocks in the IWD, especially in the Haditha vicinity [23].However, they are only well-developed in parts B and C of IWD (Figs. 1 and 2).Good examples are Um Chaimin sinkhole (Fig. 2a) and the Salman Roza sinkhole (Fig. 2b).In part A, very old sinkholes were responsible for the development of karst-type bauxite [13].On the surface tens of sinkholes can be found in Part B [20], whereas in Parts C and D very rarely sinkholes can be found, as well as in Part D.

Valleys.
Although valleys can be found in all parts of the IWD (Fig. 1); however, at each part, valleys have their characteristics (Table 1); therefore, are considered a Geodiversity.Rarely the characters in a part are recognized in other parts; however, the same valley has different characters in different parts (Fig. 3a), this is attributed to 1) the type of the rocks, 2) the regional gradient, 3) the direction of the regional gradient, 4) size of the valley, and 5) the effect of the surface and subsurface structures; including lineaments.A typical deep valley is shown in Figure (3b).and 4) in the IWD.They form very wide horizontal plains covered by a thin veneer of reddish-brown residual soil with a thickness of (0.5 -1) m; however, near H1 vicinity, a thick conglomerate (0.5 -2 m) covers considerable parts of the plateau [3], we will call it H1 Plateau (Fig. 4a).The height of the cliffs ranges from (2.5 -8) m [17].
Another large plateau is Al-Kherish Plateau (Fig. 4b), which extends into Syria, it is dissected by Wadi Akash, Wadi Ratgah, and Wadi Al-Manai (Figs. 1 and 5).The height of the cliffs ranges from (15 -45) m.The plateau is also covered by a thin veneer of reddish-brown residual soil with a thickness of (0.5 -1) m.  and 5).They are called locally "Faiydhat".The origins may be karst with circular shapes as in Faiydhat Talha (Part A in Fig. 1) and those near to Um Chaimin sinkhole (Part C in Fig. 1) or structurally controlled with longitudinal shapes as in Faiydhat Amij (Part B in Fig. 1, and Fig. 3a) and Faiydhat Al-Habbariyah (Part D in Figs. 1 and 5), which is one of the largest depressions in the IWD attending 35 x 75 km [8].Moreover Al-Ga'ara Depression (Fig. 1), which is the largest depression in the IWD, it is about 1383 km 2 with a rectangular shape; elongated in an E -W direction and limited by four rims [22].It is located in the center of Figure (1).3.1.5.Hills.Hills of different shapes (Mesa and Butte), sizes, and heights can be seen at different parts of the IWD (Fig. 1).We presented 23 hills of different shapes and sizes (Fig. 1, and Table 1).Although hills are developed in all parts of the IWD; however, they have different terminologies like "Tal", "Garat", "Goor", "Jabal" or even without any prefix like "Nhaidain", "Al-Tinif", Al-Rammeen, all are isolated hills.The height of the hills ranges from a few meters up to 45 m like Tal Erenbah.Some of the hills are more than one, like Al-Afayif (Three isolated hills, Fig. 7a), Tlelat Al-Zurug, Goor Al-Fhaimy, and Al-Ramameen.These diversities in shape, size, number, and even terminology make the hills to be an excellent example of Geodiversity.

Lithology
The majority of the existing geological formations in the IWS (Fig. 5) consist of carbonate rocks, especially the Tertiary formations, and they are exposed in all four parts of the IWD.However, the Cretaceous and Jurassic formations consist of clastics overlain by carbonates.Only in Part B of IWD (Fig. 1) there are only carbonates, with rare marl and exceptional gypsum exposed in the Fatha Formation in Hit -Kubaisa vicinity.The Triassic rocks are mainly limestone and marl, whereas the Permian rocks are mainly sandstone and claystone, and are exposed only in Part A of IWD (Fig. 1).These differences in the type of the exposed rocks at the IWD, are good examples of lithological diversity, which is a part of Geodiversity.

Faults.
Although the whole IWD is considered tectonically a stable part [6], however, a few faults have developed.They are developed mainly in Part A and very few in other parts (B, C, and D) (Fig. 5), and all are with NW -SE trend; however, very few are with E -W trend (In parts B and C, Fig. 5).It is worth to mention that the Abu Jir Active Fault Zone runs in parts A, B and D, it forms the tectonic boundary between the stable and unstable parts [6].

Age of the Exposed Geological Formations
The exposed rocks of geological formations in the IWD (Fig. 5) show significant diversity in different parts.In Part A, the age of the exposed rocks ranges from Permian -Pliocene, in Part B, they range in age from Eocene -Miocene, in Part C, they range in age from Cretaceous -Eocene, and in Part D, they range from Cretaceous -Oligocene.Therefore, different fossils can be found in the four parts of the IWD, we added two index fossils (Fig. 10).

Economic Deposits
The IWD is a potential area for different economic deposits (Table 1), which all are of sedimentary origin.Part A is the most significant and can be considered the most potential economic part including phosphate, iron (Al-Hussainiyat Mine), kaolin (Duwaikhla Mine), bauxite, glass-sand (Urdhuma Mine), palygorskite, limestone, dolomite, gas, uranium, and gold.However, some of them like gold and uranium need more exploration to prove their economic potential.Limestone and Dolomite, are present in enormous quantities in all parts.In Part B, gypsum and bitumen (in Al-Jabha and Abu Jir, Figs. 1 and 11), are the main economic deposits.In Part C, limestone, dolomite, porecelanite, and gas are the main economic deposits, whereas in Part D, limestone, dolomite, feldspar, and celestite are the main economic deposits.These large ranges of economic deposits in the IWD make the presence of economic deposits a geodiversity aspect.

Quarries and Mines
Different quarries and mines for different deposits occur in all four parts of IWD (Table 1 and Fig. 1).However, Part A includes more mines and quarries than other parts.It is worth mentioning that some of the mentioned deposits in the Economic Deposits (Subchapter 3.

Groundwater
Groundwater characteristics in the IWD are quite different in the four parts [2], this is attributed to 1) Exposed and subsurface rock types, 2) Topography and regional relief gradient, 3) Annual rainfall amounts, 4) Distance from the Euphrates River, 5) Existence or otherwise of Artesian aquifers, and 6) Surface and subsurface structures (folds, faults).The following characteristics are compared in the four parts of IWD.

Water Table.
The water table in Parts 1, 2, 3, and 4 are at the following depths (m, a.s.l.), 200 -500, 50 -175, 200 -500, and 50 -200 m, respectively.These large differences in the water table in the four parts are part of the geodiversity in IWD.

Artesian Condition.
The artesian condition was recognized in the IWD only in Parts B and D (Table 1) [2].However, in Part D the yielding water includes a high amount of hydrocarbon, mainly due to the Abu Jir-Euphrates Active Fault Zone, and fresh water in the Part B.

Aquifer Lithology.
The main rock type in the groundwater aquifers in all parts of the IWD is limestone of different formations.However, in Parts A and D, there are rare sandstone and conglomerate beds with limestone beds, respectively (Table 1).3.7.5.Springs.Springs are very rare in the IWD.Only in Parts B and D (Fig. 12), there are water springs.
In the former, they yield fresh water, whereas, in the latter, they yield brackishhighly brackish water; contaminated by hydrocarbons; however, some of them yield fresh water.The yielding water can be used for health care and the springs for tourism activities.(Fouad, 2007).The former is concentrated between Hit and Kubaisa towns (Fig. 1), whereas, the latter is located near Kubaisa town and started in 1999, it is locally called Si'eara [5].  1 and Table 1).

Petroglyphs and Artifacts
Petroglyphs and artifacts are traces of prehistoric humans.In the IWS, only in Part A petroglyphs (Fig. 14.a) and artifacts (Fig. 14.b) were found, both in Al-Ga'ara Depression.They are a good indication of the presence of ancient humans and different types of animals that do not exist anymore.In the other three parts, no petroglyphs and/ or artifacts were found; however, this doesn't mean that they do not exist.

Discussion
Geodiversity of scientific value can be either geosites or geoheritage elements that are ex situ.Similarly, geodiversity that is of little or no scientific value may be categorized as sites of geodiversity or geodiversity elements that are ex situ [4].We have presented different geodiversity data in the IWD, some of the presented data can be categorized as sites of geodiversity (Geosites), which means in situ, or geoheritage elements, which means ex situ.A good example of the geosites (in situ) is Al-Ga'ara Depression in Part A (Fig. 1), where different elements (aspects) can be seen (Table 1 and Figs.1, 7 a, and 14).These are developed by different geological environments of deposition (Marine and continental), weathering, and erosion (both of different types and agents) that have developed tens of features and forms, which are excellent examples of geodiversity.Among them are: 1) Rock types, 2) Fossils (Fig. 10), 3) Mineral deposits, 4) Geomorphological forms and features, and 5) Structural elements (Faults and folds).Examples of geodiversity elements, which are developed in all four parts of the IWD are: 1) Valleys of different shapes, 2) Plateaus of different extensions and sizes (Fig. 4), 3) Isolated hills (buttes) of different heights (Fig. 7b), 4) Quarries of different mineral deposits (Fig. 11), 5) Petroglyphs and artifacts (Fig. 14), 6) Sinkholes (Fig. 2), and 7) Bitumen seepages and Eternal fire (Fig. 13).Moreover, the used terminology by the local people of the IWD is quite different in different parts of the IWD, and even between people living in urban areas from those living in rural areas, and more specifically those who are living in the desert area; called "Badoo".For example, an isolated hill is called "Tal", in urban areas and rural areas, and "Gara" by Badoo.The plural of the "Gara" is "Goor", and the "Tal" is "Tlool" and when are small, they are called "Tlailat".

Conclusions
The Iraqi Western Desert (IWD) includes geodiversity features and forms.We divided them into 10 main types and 27 sub-types.We also divided the IWD into four parts (A, B, C, and D) to present different geodiversity types and sub-types.To elucidate the locations of the existing geodiversity types and sub-types, we presented a satellite image showing the locations.We used special symbols and abbreviation letters to indicate the presented geodiversity.In total, 54 locations are indicated on the satellite image.The existing geodiversity types represent in situ and ex-situ elements.

Figure 1 .
Figure 1.Satellite image of the Iraqi Western Desert with the main Geodiversity data.A, B, C, and, D are the four divided parts.For the used abbreviations refer to Table (2).

Figure 2 .
Figure 2. a) Satellite image of Umm Chaimin sinkhole with tens of circular depressions, f-fꞌ is a fault, and l-lꞌ are lineaments, and b) Salman Rosa sinkhole.For location refer to Figure (1)

Figure 3 .
Figure 3. Wadis, a) Akash near Akashat town in parts A, and b) Al-Qasir, south of Anah town, Part B.

Figure 4 .
Figure 4. Satellite images of plateaus in IWD, a) H1 Plateau west of Wadi Hauran, b) Al-Kherish Plateau, west of the Wadi Akash, note it extends in Syria.

Figure 7 . 9 Figure 8 .
Figure 7. Isolated hills, a) Al-Afayif (At Al-Ga'ara Depression), the height is about 45 m, and b) East of Rutbah town, the height is about 50 m, and c) Near Al-Doolab, the height is about 15 m.

3. 3 .
Structural Geology 3.3.1.Folds.The Anah anticline is the only present surface fold at the IWD, it extends within Parts A and B (Figs.1 and 5).However, a subsurface Akkas anticline exists in Part A (Fig.8a) as it appears from the exposures of the Euphrates Formation in Wadi Al-Mana'i and Wadi Al-Ratgah, which show closures of the exposures from the north and south along both wadies (Fig.9a, marked by red arrows).No other fold is recorded in the IWD.However, the rocks west of Al-Ga'ara Depression at Part A (Figs.1 and 8b) are highly and intensely jointed, and no such jointed rocks can be found in the other three parts (B, C, and D).Another unique form is the seismicite structure, which is developed in the uppermost part of the Euphrates Formation; only in Part B[18].

Figure 9 .
Figure 9. a) Geological map showing exposure pattern, which indicates the presence of the subsurface Akkas anticline marked by red arrows, b) Intensely jointed rocks west of Al-Ga'ara Depression.Both locations are in Part A, c) Seismicite structure north of Hit town

Table 1 .
Summary of Geodiversity types present in the Iraqi Western Desert