Main Subjects : Geotectonics

The Influence of Shell Permeability on Stability of Upstream Slope during Rapid Drawdown – Khassa Chai Earth Dam as a Case Study

Krikar Noori; Sirwan Salim

Iraqi National Journal of Earth Science, 2021, Volume 21, Issue 2, Pages 15-28
DOI: 10.33899/earth.2021.170383

Several factors affect the stability of earth dam during sudden drawdowns such as permeability and mechanical properties of soil, upstream side slope, drawdown ratio, and drawdown rate. This paper investigates the influence of shell permeability on earth dam upstream slope stability and its role in the change of pore water pressure at different locations of the embankment during the sudden drawdown, using different limit equilibrium methods. To accomplish the objective of this study, (Geo Studio 2012 Software) as one of the powerful geotechnical programs was used for the modeling and numerical analysis. The study shows that decreasing in the shell permeability resulted in the reduction of pore water pressure dissipation and variation of shell hydraulic conductivity plays a vital role in the overall stability of the upstream slope under rapid drawdown conditions.

Selection of the Optimum Sites for the Wind Turbines Installation in Nineveh Governorate by using GIS

Ghada Younis; Sabah Ali

Iraqi National Journal of Earth Science, 2021, Volume 21, Issue 1, Pages 1-16
DOI: 10.33899/earth.2021.170376

Green energy, including wind energy, becomes a vital component of reducing air pollution and enhancing its sustainability. Wind energy production increases rapidly due to its significant turbine technologies, compatible with sources of energy-environment friendly in reducing Carbon emissions. This paper presents an evaluation of wind power potential of Nineveh governorate in the northern part of Iraq based on the GIS technique using 20 years daily wind speed and direction at elevation 10m, 50m on earth surface covering the period of 2000 to 2019 obtained from NASA agency. It is observed that Nineveh Governorate and its surrounding have a wind speed between 2.8 and 3.7m/s at 10m, and wind speed between 3.9 and 5.3m/s at 50m. The annual mean power density ranges from 54 to 124 W/m2 at 50m.These results indicate that the monthly variation recorded for the speed is maximum 3.7m/s at 10m and a value of 5.3 m/s at 50m in the northwest direction in Hadhar site which matched with the results obtained by GIS/ IDW interpolation map of the power density.

Effect of Tectonostratigraphic Units in Evolving Aqra Anticline Model

Mahmood Al-Sumaidaie; Nabeel Al-Azzawi; Rabeea Znad

Iraqi National Journal of Earth Science, 2020, Volume 20, Issue 2, Pages 126-147
DOI: 10.33899/earth.2020.170374

In the current study, a tectonic model for the structure of Aqra Anticline was proposed. The model was dependent on the rock properties, stratigraphic relationships and thickness variations as well as, the model was correlated with other previous studies. The study area is located within the Iraqi Zagros fold/ thrust belt (ZFTB) which represents the northeastern margin of the Arabian Plate.
Stratigraphically, the anticline comprises of formations that are deposited between Early Cretaceous to Pliocene periods. These formations are the Sarmord, Qamchuqa, Aqra, Kolosh/Khurmala, Gercus, Pila Spi, Fat'ha, Injana, and the Makdadiya formations. they were deposited during four Tectonostratigraphic Megasequences (TMS). The older TMS contains formations that were deposited prior the development of the Zagros Foreland Basin, whereas the formations of other three Megasequences were deposited within Zagros Foreland Basin. During those times, the foreland basin was divided into three distinct parts. these are fore deep, bulge, and fore-bulge, which   were discriminated via listric faults, which played as normal and reverse displacements after and before ophiolite obduction.
Some contributions to the tectonostratigraphic model of the area are adopted. They are stages of basin development, determining the time of extension period of the listric faults and detecting the tectonic inversion of these faults. This model is described within the compressional tectonic framework between the Arabian and Eurasian plates.

Determination of Geotechnical Properties of Local Claystones in Northeast Koya City, Iraqi Kurdistan Region

Nawzat Ismail; Hemn Omar

Iraqi National Journal of Earth Science, 2020, Volume 20, Issue 1, Pages 1-14
DOI: 10.33899/earth.2020.170286

The aim of the current study is to determine the geotechnical properties of the investigated claystones /clayey soils in Koya area, Iraqi Kurdistan Region. This paper deals with the evaluating of the physical, mechanical and index properties of claystones. The study based on the field reconnaissance for twenty-five claystones samples were collected from five outcrops location within Fat'ha Formation. The results obtained from the laboratory tests revealed that the averages of specific gravity, porosity, void ratio, water absorption, natural water content and uniaxial compressive strength values of claystones are (1.5, 4.45%,4.5, 0.3, 3%, 65 MPa) respectively. Whereas the results of the index geotechnical characterization of clayey soils revealed that the averages values of liquid limit, plastic limit, plastic index, flow index, toughness index, liquidity index, consistency index, swelling potential, activity index, and expansive potential are (25.2, 15.0, 10.2, 0.2, 0.5, -1.2, 2.2, 0.62, 0.31, low or non-expansive) respectively. Among the index properties, the clayey soils are suitable for foundation and building materials industry. Furthermore, the regression coefficients of their correlation (R²) obtained from the analysis show that there are strong relationships between the physical and mechanical properties of claystones. Concluding remark is that geotechnical properties of examined natural claystones satisfy the relevant regulation to be used for construction purposes.

Morphotectonic Evidences for Strike-Slip Component of the Reverse Fault at the Southeastern Plunge of Bashiqa Anticline

Alaa Hamdon

Iraqi National Journal of Earth Science, 2020, Volume 20, Issue 1, Pages 15-23
DOI: 10.33899/earth.2020.170315

Sedimentary rock beds and drainage pattern offset took place predominantly at the southeastern plunge of Bashiqa anticline which indicates shear zone in this area represented by apparent left-lateral fault separation of reverse fault dipping to the southeast. This study will discuss and update the geological information of the impressions of the fault on the surface topography based on the morphotectonic evidences including visual interpretation of the satellite image for the landforms and regional stress analysis of the study area. The variations of landform features are regarded as an efficient geological indicator for tectonic activity in the area.

Inferred Inversely Reactivated Listric Fault at Chia Gara Anticline, Northern Iraq

Ibrahim Aljumaily; Nazar Abdullah

Iraqi National Journal of Earth Science, 2019, Volume 19, Issue 2, Pages 11-25
DOI: 10.33899/earth.2019.170280

Chia Gara anticline is an E-W extending doubly plunged fold, parallel to the Taurus Mountains having about (80) km length and (12) km width. It is located within the high folded zone of northern Iraq. The exposed rocks range in age from Late Triassic to Late Miocene. Structural analysis of the anticline performed through three traverses transverse to the general fold trend from western plunge zone towards east. Geometrical analysis of fold elements shows that Chia Gara anticline is asymmetrical vergingtowards north in both first and third traverses, whereas it is more or less symmetrical in the second traverse. Meanwhile, results of Fourier analysis demonstrates that the fold form is more developed in the northern limb of the anticline than in its southern limb, in the first and third traverses. Nevertheless, in the second traverse, the fold form seems more developed in the southern limb compared with the northern limb. The northern vergence of the anticline and its advance development in northern limb in the first and third traverses may reflect the impact of a suture vergent reversely slipped listric fault beneath the anticline sectors in these traverses. However, the obscure of such listric fault in the second traverse may be due to the effect of a sinistral (BF1) and a dextral (BF2) subsurface strike-slip faults transverse to the trend of Chia Gara anticline on either side of the second traverse. The surface expressions of them, as well as others like Zewa and Deralok faults (dextral) are evident in satellite image of the area. The southward pushing of the wedge between (BF1) and (BF2) had opposed the northward reverse displacement of the proposed listric fault beneath thesecond traverse. The effects of these strike-slip faults (BF1) and (BF2) are evident also in anticlockwise deflection of both axial plane and fold axis attitudes from first to the second traverse, and vice versa from second to the third traverse.

New Petrophysical Equations for Hartha-Tannuma Interval in the East Baghdad Oil Field

Maan Al-majid

Iraqi National Journal of Earth Science, 2019, Volume 19, Issue 2, Pages 136-152
DOI: 10.33899/earth.2019.170285

This study deals with empirical equations linking density and porosity with depth. The density and porosity information were taken from five well logs distributed in the East Baghdad oil field. New empirical equations (porosity - depth, density - depth) for two geological formations (Harta and Sa'di) within Hartha- Tannuma period were produced. The correlation coefficient (R) of these equations ranged from -0.37 to 0.68, which was attributed to variability in lithology and compaction. The depth data of (133) points suited at seismic lines grid scattered in the field were used for applying the new equations. After the new empirical equations that are applied on the whole field, porosity and density contour maps for the period (Hartha- Tannuma) and the two formations (Hartha and Sa'di) were plotted. The high porosity zones were identified, are related to the compaction and petroleum distribution in the field.

The Structural Development of Folds Shapes in the Western Zagros Fold/Thrust Belt of Iraq Using Fourier Analysis

Nabeel Al-Azzawi; Nazar Numan

Iraqi National Journal of Earth Science, 2019, Volume 19, Issue 2, Pages 26-41
DOI: 10.33899/earth.2019.170283

Depending upon the geometrical shapes of the fold profiles, the Western Zagros Fold/ Thrust Belt of Iraq has been subdivided into different geometrically distinctive and genetically significant four sectors using Fourier ratios suggested by Hudleston classification. Furthermore, the same belt has been subdivided into eight sectors using Singh and Gairola's classification. The sector names of the former are chevronic–sinusoidal, sinusoidal–parabolic, parabolic–semi elliptical and semi elliptical–box fold styles. Whereas in the later division, the sectors are almost chevronic, chevronic–sinusoidal, almost sinusoidal, sinusoidal–parabolic, almost parabolic, parabolic–semi elliptical, almost semi elliptical and semi elliptical–box fold styles.
         The investigation involves harmonic analysis (Fourier analysis) of the fold profiles by solving Fourier equations using the Gauss elimination method, determination of Fourier coefficients and Fourier ratios for forty major anticline structures that cover fairly evenly the Western Zagros Fold/ Thrust region. The procedure of harmonic analysis is carried out with FOLDN, a GWBASIC program written for this purpose. Fourier ratios are utilized for distinguishing different types of fold shapes.
         In general, the map of these sectors shows that the folds become progressively more developed in shape towards the north and northeast. The arrangement of the obtained fold sectors in the studied area, matches the folds initiated first near the Alpine Suture and with time, they propagated south and southwestward across the axis of orogeny. In addition, probably the process is still going on.

Structural and Tectonic Study of Qara Sard Anticline and Choplagh Syncline, from Sulaimaniya Area, Kurdistan Region, Northeastern Iraq

Saddam Al-khatony; Nabeel Al-Azzawi; Fadhil Lawa

Iraqi National Journal of Earth Science, 2019, Volume 19, Issue 1, Pages 39-58
DOI: 10.33899/earth.2019.170270

The study of the structural geology and tectonics of Qara Sard anticline and Goblagh syncline is carried out within the northwestern part of Zagros Fold-Thrust Belt (ZFTB) in Sulaimaniya area, Kurdistan region, Iraq. Qamchuqa Formation (Early Cretaceous) builds up the core of the anticline and overlain by Kometan, Shiranish and Tanjero formations (Late Cretaceous). Moreover, Khalakan Formation overlies Kometan Formation on the northeastern limb of the anticline. Tanjero Formation appears at the core of Choplaghsyncline. The structural geometrical analyses of seven traverses (P) cutting across the anticline and the syncline, revealed that the two folds are double plunging, and asymmetrical in all traverses except in P5 and P6 in Qara Sard anticline. Both folds are verging toward northeast; however, the anticline verges toward southwest and being vertical in P4 and P5 respectively. The geometrical analysis using PI diagrams reveal that the fold axis of Qara Sard anticline is sinuous and changing its trend in three attitudes. The first is NW-SE in the traverses P1, P2 and P3 with gradual clockwise drifting. The second one is WNW-ESE in P4, P5 and P6 and then returning in the third to the first attitude NW-SE in the traverse P7. Consequently, the area was influenced by four strike-slip faults. They are either transverse or inclined to the fold axis. These faults are Dolma Reza dextral, Choplaghsinistral, Lower Zab dextral and Dokan sinistral. They divided the area into four blocks moved in opposite directions depending on the strike-slip faults displacements. On the other hand, the study folds are affected by three reverse listric faults. They are suture-verged and parallel with the fold axis. Two of them affected the northeastern limb of Qara Sard anticline, whereas the third disturbed its southwestern limb. By investigations of the vertical changes of fold style, the reactivation of the suture listric fault (2) is detected. It appears as a rotational type so as its larger effect is on traverse P7 and its displacement is gradually reduced toward P4. Moreover, the reactivation time of this suture rotational listric fault was Turonian, it is reflected throughout verging change of the fault between Qamchuqa and Kometan formations in traverse P6.