Iraqi Bulletin of Geology and Mining

Sixty meters thick Oligocene carbonate succession crops out in the area southeast of Derbandi Khan town and northeast of Kalar town. The carbonate succession is exposed in the core of the NW – SE trending Sharwaldir anticline, which extends across the border into Iran. The recorded facies have stratigraphical and paleogeographical importance for understanding of the palaeogeography of NE Iraq; the facies are: Foraminiferal wackestone – Packstone, Bufflestone, Algal – Coral bindstone, Bioclast wackestone – Packstone and Grainstone microfacies. These facies indicated that the lower, middle and upper parts of the section are deposited in fore-reef, reef-crest and reef-back reef environment, respectively. They belong to Baba and Anah formations (lower and upper parts of the section, respectively) while the middle part is a transitional zone between the two formations. The chemistry of the carbonates showed them to be of good quality for Portland and white cement production.

Many outcrops of crenulated limestones are observed in eastern part of Sulaimaniyah area. These limestones are deformed into tight and/ or open mesoscopic folds, which are superimposed on larger-scale synclines or anticlines. The outcrops are discussed and the biostratigraphically is analyzed. The identified planktonic foraminifera indicated that these limestones belong to Kometan Formation and its age extends from Turonian to Late Campanian. The age determination depends on the index planktonic foraminifera; such as Marginotruncana sigali and Dicarinata imbricate indicate Turonian age, whereas Dicarinata primitivae indicate Coniacian age, Dicarinata asymmetrica, indicates Santonian age and Radotruncana calcarata indicates early Late Campanian age.

A new species of foraminifera related to the family Orbitolinidae, Orbitolina arcuala sp. nov., is observed and described from the Late Albian part of the Mauddud Formation (Late Albian – Early Cenomanian) of Iraq. Its identification depends on the morphology and the internal structural features of the test. To achieve this aim, thin sections have been prepared from core samples collected from Kirkuk well 109. Two supplementary thin sections are used, one from Cham Chamal well 1 and the other from Nafatah well 1; to confirm definition and geographic extensions.

This new identified species differs from the other species of the genus Orbitolina d'Orbigny, 1850 (subfamily Orbitolininae), by the presence of a depression on one side near the embryonic area and by the presence of a perfect, well-developed periembryonic area, in addition to the differences in the dimensions and other features, all features are within the valid definition of the genus Orbitolina.

The Sarmord Formation in the study area is mostly composed of dolostone rich in bituminous materials. Due to the presence of bituminous materials, most of the rocks have dark grey to grey and black color and interbedded with fissile black shale. The present study is mostly based on 23 samples obtained from 5 surface sections and 2 spot samples emphasizing their lithofacies, fossil contents, diagenetic processes, diagenetic environments, distribution of bitumen and environment of deposition. Detailed petrographic examination of the rocks has led to the distinction of four main lithofacies, namely limestone, dolostone, siliceous rocks and shale. Several diagenetic processes are observed to have affected the rocks of this formation including dolomitization, which appear to have been widespread, physical and chemical compaction, neomorphism, leaching and porosity development, cementation, silicification and calcitization (vanished evaporite). Most of the diagenetic processes might have taken place in deep burial environment, shallow subsurface evaporatic environment and submarine environments.

Many types of bitumen accumulation can be distinguished in the studied formation. It occurs as beds, laminae, pore filling, coating, and inclusion and as lining stylolites. The depositional environment was so difficult to be deduced due to the severe dolomitization process, which obliterated the original texture and structures of the rocks as well as the fauna. Nevertheless, the presence of some fauna and the remained texture and structures indicate that the deposition of the formation belongs to deep marine shelf margin environment of normal salinity.

The gabbroic members of the igneous rocks from the Mawat Ophiolite Complex are located in the Zagros Suture Zone at the boundary between the Arabian and Iranian Plates. They are related to post collision event with emplacement into the continental crust after collision (during Tertiary) between the Arabian and Iranian Plates.

Three types of gabbroic rocks were recognized and studied: 1) The layered gabbros, which are the dominant type; 2) The marginal gabbros are the most affected by alteration and deformation among the three types of the gabbros, and 3) The dyke pegmatoid gabbros. The layered gabbros exhibit two types of layering; compositional layering and grain size layering. Mechanical crystal settling is considered as the main process of layering.

In this study, the petrographic study of 100 thin sections showed that these rocks consist of calcic plagioclase, bytownite in composition (An 85), clinopyroxene (augite) and rarely orthopyroxene, as the major mineral phases. Iron oxides, mainly magnetite is found as an accessory primary phase and as secondary after the Fe-Mg bearing mineral phases. The rocks in general, experienced alteration with the formation of different secondary minerals. Amphibole (Tremolite – Actinolite) is abundant as alteration product of the primary pyroxenes; associated with chlorite, epidote, sericite and secondary magnetite. Plagioclase attained relatively variable degrees of alteration. Three types of deformations were recognized; crystal-plastic, semi-brittle and brittle. Pseudomorphic and non-pseudomorphic alterations were distinguished. The marginal gabbros are most affected by alteration and granulation. Primary magmatic textures include hypediomorphic granular, intergranular, poikilitic, ophitic and sub ophitic textures, whereas deformation textures are evident by granulation, secondary twinning, and schistose textures.

Sedimentological study of Mukdadiya Formation (Late Miocene – Pliocene) indicates that its sediments were deposited in fluviatile meandering channels system. The sequence of the formation is composed of several fining-upward cycles in which three facies were recognized: The sandstones facies, represents channels deposits, the gravelly sandstones and conglomerates facies, represents a high energy environment reflecting a climatic or tectonic pulses in the source area, and the fine grained sediments facies, represents overbank deposits.

The petrographic study of the sandstones of Mukdadiya Formation indicates that they are immature, mostly poorly sorted and classified as litharenite. They are composed mainly of quartz and sedimentary rock fragments; the predominant type of sedimentary fragments is carbonate. The study of heavy minerals indicates that epidote group is forming the main heavy minerals, followed by amphibole, pyroxene and garnet. The source rocks; based on petrographical and heavy minerals studies are interpreted to be composed essentially of sedimentary followed by igneous and metamorphic rocks.
The study of clay minerals indicates the presence of montmorillonite, chlorite, illite and kaolinite. The origin of most of these minerals is detrital, however, the chlorite is considered to be partly diagenetic.

The Iraqi Southern Desert is covered mainly by limestone pavement, being mainly composed of Paleocene – Pliocene rocks, which belong to Umm Er Radhuma, Dammam, Euphrates and Zahra formations. The most karstified rocks, however, belong to Dammam Formation of Eocene age. The Dammam Formation consists mainly of limestone, with dolostone, dolomitic and marly limestone, and marl. Some chert nodules or bands occur too within the succession.
Morphologically, the Iraqi Southern Desert comprises mainly of flat terrain, which is dissected by dense drainage system, and slopes towards north and northeast. Therefore, the main valleys flow towards north and northeast, with almost parallel courses. However, the course of the valleys within the rocks of the Dammam Formation exhibit strange and abnormal forms, which are not usual in normal drainage patterns. The abnormal forms are like bifurcation of the valleys; downstream and joining again, and circular and crescent forms, besides changing their main flow direction. These abnormal forms are believed to be due to the influence of the karstification, which is still an active process. The karst forms are in circular, oval, polygonal and crescent shapes, with different sizes. The karstification is not only obvious in the drainage forms, but also in the exposed rocks. They exhibit successive and parallel rims, which coincide in shape and direction with the karst forms, indicating continuous karstification. The karstification stages, sizes, types and reasons are mentioned too, with many examples from the abnormal drainage forms.

The author has many remarks on the work published by Amer, R.M. (2011) in Iraqi Bulletin of Geology and Mining Vol.7, No.3, p. 19 – 47, concerning the stratigraphy of the Ms'ad Formation in the Iraqi Western Desert, particularly on the recognized formations in the studied borehole A'awaj 1.

Herewith is a point-by-point reply to the discussion of Mrs. Sahira M. Karim concerning the aforementioned published article.

The age and stratigraphic succession of the exposed and subsurface rocks, and according to the foraminiferal assemblages two important planktonic species were determined: Rotalipora greenhornensis (RENZ) of Late Cenomanian age and Helvetoglobotruncana helvetic (BOLLI) of Turonian age, accordingly two biozones were identified:

This research concerns with the study of the Late Quaternary sediments in Bahr Al-Najaf Depression central part of Iraq. To perform the research, grain size analysis and heavy minerals were studied in one section that includes these sediments, and to study the changes in the type of the depositional environment, and distribution of these heavy minerals; when they were transported from the source area to a new environment; in the depositional area.

Grain size analysis of 23 samples collected from the site, showed that these samples consist mainly of clay and silt with subordinate sand. The heavy minerals study of medium to fine grained size (250 – 63 μm (sand fraction of 17 samples from the sediments of the same site, showed prevailing of those unstable minerals (represented by amphibole and pyroxene minerals) with a relatively high amount of opaque minerals.

This study includes petrography, mineralogy and chemical analysis of sediments of the Dibdibba Formation, which is exposed along Tar-Al-Najaf. The obtained results show that the Dibdibba Formation contains about 72% sand. Sand is essentially of coarse and medium – coarse sized, the average percentage reaches about 63%, which refer to precipitation of the sediments in active environment. Sandstones of Dibdibba Formation consist essentially of quartz including mono-crystalline quartz, which reflects the igneous origin and poly-crystalline quartz, which reflects metamorphic and potash-feldspar; represented by orthoclase and few microcline, sodic feldspar; represented by albite and trace or obscene of calcic feldspar.

According to the needs of Naenava Governorate for manufacturing building fired-bricks the, this work was conducted to evaluate the suitability of the exposed claystones within Injana and Mukdadiya formations in Al-Kind Hills region for such industry. Twenty three clay samples were subjected to crushing, quartering, dividing, and then testing to indicate their chemical, physical and mineralogical properties. The samples were extruded to have dimensions of (2.5 x 3.85 x 7.5) cm, which were then dried at room temperature for 48 hr and for 24 hr at 110° C, using laboratory oven. Different variables were studied including particle size reduction of representative sample for the whole region (+ 150 and – 150) µ, adding river sand (10 and 20) %, and then changing in firing temperature (700, 750 and 800 ºC). The firing of the brick samples were carried out at a certain program; for 2 hr socking time.

The resulted samples were tested for their physical, mechanical and mineralogical properties and then the results were compared with the requirements of the Iraqi Standard Specification No.25, 1993. The results indicated that the claystones under study were suitable for brick manufacturing. The test results of some samples fired at 800 ºC were found in accordance with the mentioned standard specification.