Syncline contribution to mountain peak building: examples from Western Zagros,Kurdistan Region,Northeastern Iraq

The current study focuses on roles of the synclines in building mountains of the Zagros Fold-Thrust Belt from Northeastern Iraq, Kurdistan Region. The studied area is located in the Imbricated Zone, which is a continuation of Simply Folded Zone of Iran. In some parts of this zone, the synclines contribute to building nearly half of the mountains and increase the relief contrast of the landscapes. The role of syncline in building mountains is opposite to its apparent intrinsic shape which is located in low land and normally forms synclinal valleys. In studied area, this phenomenon is observable in the areas that are complexly deformed, deeply exhumed, and predominately composed of the carbonate rocks. In these areas, exhumation and stream erosion have removed high thickness of overburden rocks and the tectonic stresses have crenulated carbonate rocks in the synclines. Due to these processes, these synclines are observable on the peak of the mountains now. The contribution of synclines in mountain building is related to three properties: the first is folding of synclines in confined condition (relative to anticlines) by which they have transformed to highly compact and stiff rocks. The second is accumulation of hydrothermal or meteoric water in the synclines due to its downward bending which aids precipitation of minerals and heals the possible tectonically and lithostatically induced fractures. The third is ductile deformation of synclines in confined and deeper level as compared to brittle deformation of anticlines in relatively shallower level and unconfined condition during deformation. Consequently, these factors result in an inversion of topography by which synclines are remained as mountains (high topography) above surface during exhumation while erosion removes anticlines. The result of this study is applicable for geological, geomorphological, and structural mapping in highly deformed and deeply exhumed terrains. The possible prediction of geomorphological position of synclines and anticlines on the mountain peaks and valley bottoms respectively is the applicable result in the above terrains.     

Morpho-Structural Study of the Korek Anticline,Zagros Fold-Thrust Belt,Kurdistan of Iraq

The present study is an attempt to construct a morpho-structural model for the Korek anticline that is located within the High folded zone of the Zagros Fold and Thrust Belt in the Northern Iraq-Kurdistan region. A detail geological map constructed for this structure, the stratigraphic succession that is exposed in the area was deposited from the middle Jurassic up to upper Cretaceous, and consists of nine formations. The most important morphological landscape and landforms in the studied area are due to endogenic and exogenic processes. Accordingly, the area is divided into four main units, which are units of structural, denudational, fluvial and solution origins. Each unit characterized by its own morphological feature differs from one another. According to structural point of view the field data are analyzed from two point of the viewing, one from map view and secondly from cross sections. The geometrical properties from map view of the Korek Anticline indicated that this fold is an asymmetrical double plunging, open to gentle, non-cylindrically curviplanar fold. The Korek Anticline becomes sharper with the depth, but broader and more open upward, this is one of the most characteristic features of the parallel fold (Class 1B). The presence of numerous reverse faults and strike-slip faults which affect the architecture of the Korek Anticline indicates that this Anticline formed by a Fault-propagation fold mechanism. Detailed balanced and retro-deformable cross sections along this anticline indicate that the shortening percentage can be differentiated in space and times, while the depth to detachment gives values that iscoincident with the Ora Shale Formation of Paleozoic age. A morpho-structural model was constructed for this structure and it consists of two main stages and five substages were responsible for the formation of the Korek structure. The first main stage belongs to structural construction, which consists of three sub-stages, while the main second stage is belonging to morphological destruction, which consist also two sub-stages. The effect of these stages and sub-stages makes the anticline to take the nowadays architects shape.     

The geochronology and petrogenesis of Walash volcanic rocks,Mawat nappes: constraints on the evolution of the northwestern Zagros suture zone,Kurdistan Region,Iraq

Geological, geochemical, and geochronological investigations of the upper volcanics (UV) of Lower allochthon (LA) of Mawat nappes (MN) were used to elucidate the geologic relationships between the LA, the Qulqula Rise (i.e., accretionary complex terrane (ACT)) and peripheral Foreland Basin Assemblage (FBA), (Maastrichtian–Paleogene). The ⁴⁰Ar-³⁹Ar geochronological data suggest that the Middle to Late Paleogene magmatic history of Late Walash arc volcanic activity of UV can be divided into an early phase of andesitic volcanism around 43.1?±?0.3 Ma and subsequent extensional arc phase magmatism of a time lapse between 40.1?±?0.3and 32.3?±?0.4 Ma. The geochemical data establish the existence of gradients in trace element ratios (i.e., Ba/La, Th/Yb, U/La, Ba/Th, Rb/Y, Ba/Y, and Nb/Y) throughout the studied samples and reflect differences in the degree of mantle wedge depletion influenced by addition of a considerable proportion of sedimentary derived input of the subducting Arabian slab. The trace, rare earth elements and isotopes of the studied samples have emphasized differences in the geochemical characteristics of andesites in comparison with other members of Walash. The andesites have subduction-related signature with the isotope (low Nd and high Sr isotope ratios) characteristic of a melt component input from cratonically-derived sediments. The diabases intruding in the basalts and andesites have a transitional composition from andesitic to N-type mid-ocean ridge basalts geochemistry with a noticeable subduction-related signature, and are interpreted to form in an extensional arc evolving into back arc basin setting. As evidenced from infant arc magmatism (Albian–Cenomenian), MN recorded protracted kinematic at convergent plate margins with a most notable was the development of the ACT (i.e., Qulqula Rise) adhered to the Arabian platform carbonates (Albian–Cenomenian) leading to the inception of peripheral FBA occurred by the erosion and unroofing of advancing ACT. Notably, the volcano flysch of Walash and Nummulite carbonate of Naopurdan were still accumulating on the remaining oceanic lithosphere further to the northeast and in part coeval with Paleogene molasses sedimentation on flexural FBA further to the southwest of the ACT.     

Biostratigraphy of oligocene succession in the High Folded Zone,Sulaimani, Kurdistan region,Northeastern Iraq

Oligocene and Lower Miocene sediments from High Folded Zone of Iraqi Zagros have been studied paleontologically at south of Sulaimaniyah, Kurdistan Region, NE Iraq. The identified fauna are consisted of (25) genera and species of benthonic and (16) species of planktonic foraminifera. The fauna comprises relatively abundant foraminiferal assemblages of moderate diversity. Based on the stratigraphic distribution of these species, two biozones have been recognized which are Nummulites—Rotalia and Globoquadrina dehiscens zones. These biozones indicate that the studied sections of Basara and Khewata are of Late Oligocene–Early Miocene age. Based on the microfossils, it has been found that the age of sediments is equivalent to or represents Anah and Serikagni Formations. Some previous studies described Oligocene rocks (Kirkuk Group) as interior sag basin. In the present study, the occurrence of the group inside High Folded Zone and its rich fauna content are used for the discussion of the sag basin versus normal marine water.     

Appraisal of relative tectonic activity along the Kazerun Fault Zone,Zagros Mountains,Iran: insight from spatial analysis of geomorphic indices

This paper investigates the impact of active tectonics on the geomorphic processes and landscape evolution along the Kazerun Fault Zone (KFZ) in the Zagros Mountains of Iran using spatial analysis of geomorphic indices. We document how topography and morphology are influenced by active tectonic deformation. The Zagros fold–thrust belt is an area of active crustal shortening where northwest–southeast oriented fault‐related folds become younger from north to south and from southeast to northwest. This temporal and spatial evolution of the belt was tested using geomorphic indices of active tectonics that include mountain front sinuosity index (Smf), the valley width/height ratio (Vf), drainage basin asymmetry factor, hypsometric integral, drainage basin shape ratio and mean axial slope of the channel. Change in the geomorphic indices is the result of active fold growth and change in the uplift rate. Decreasing Smf and Vf values from north (Smf = 2.01; Vf = 0.5) to south (Smf = 1.12; Vf = 0.2) and from southeast (Smf = 1.84; Vf = 0.8) to northwest (Smf = 1.54; Vf = 0.1) points to a migration of the active crustal shortening towards W–SW. The combined geomorphic (field evidences) and morphometric data (quantitative analysis of geomorphic indices) provide evidence of relative variation in the tectonic activity along the Kazerun Fault Zone and related landforms. The utilization of geomorphic parameters with comparison to the field observations exhibits change in relative tectonic activities mostly corresponding to the change in mechanism of the prominent fault zones in the study area. Copyright © 2014 John Wiley & Sons, Ltd.     

Study of subsurface features using seismic reflection data in Erbil area,Kurdistan Region,Iraq

The present study seeks to interpret seismic reflection data for an area measuring approximately about 1,450 km² within the Erbil plain in the Kurdistan Region of Iraq to produce subsurface geological pictures. Thirteen seismic lines were identified by the Iraqi Oil Exploration Company using dynamite sources and then processed; then, a seismic line, BH-15, of around 432.5 km total length was used in this study. Three horizons (reflectors) were selected and identified by tying them directly to Demir Dagh well no. 1, these are H1, a reflector that represents the near top of the Lower Fars Formation; H2, a reflector that represents the top of the Pila Spi Formation; and H3, a reflector that represents the top of the Shiranish Formation. The qualities of the reflectors range between fair and good. All the isochrone and depth maps and 3D view pictures of the reflectors show the same main subsurface structural features trending in a NW–SE direction, namely, Erbil trough, Sherawa trough, and the southeastern plunge of the Demir Dagh anticline. Ninety-five normal and reverse-type faults trending in a NW–SE direction were detected. Also, the maps show that the reflectors tend to increase in dipping and deepening towards the southeastern and eastern parts.     

Geochemistry and genesis of sulphide ore deposits in Sharosh Village,Qandil Series,Kurdistan Region,NE Iraq

The low-grade base metal sulphide Cu–Zn–Pb and Fe mineralization of Qandil Series develop in shear zones that occur in formations of the north-western part of the Zagros Orogen. This sulphide mineralization occurs either as quartz vein type or disseminated type associated with metamorphic rocks (marbles and phyllites). This study aims to characterize these sulphide-rich ores by means of their mineralogical and geochemical features, including also the features of the corresponded host formations and those of marbles (calcitic and dolomitic) and phyllites. Petrographical data indicate the presence of Cu, Zn, Pb and Fe sulphides in hydrothermal quartz (±calcite) veins of different generations. Geochemical data of surface samples indicate enrichment of Cu and Fe in shear zones with low concentrations in Zn and Pb. The REE data indicate that the genesis of these sulphide ores took place in a hydrothermal system and was generally attributed to high temperature (> 250 °C).The mineralization seems to be fault-controlled, which is favoured by the significant tectonic deformation of the area.     

An integrated study of upper Campanian-lower Maastrichtian carbon isotopes and calcareous plankton biostratigraphy of the Kurdistan Region,northeastern Iraq

New carbon (δ¹³C) isotope records calibrated by planktonic bioevents provide general support for a late Campanian age assignment of the Shiranish Formation (Fm.) and its boundaries in the Dokan section (NE Iraq). The Shiranish Fm. is characterised at the base by a mid-Campanian unconformity as can be interpreted by absences of nannofossil zones CC20-21. The Shiranish Fm. then spans nannofossil biozones CC22-CC23a (UC15d-e^TP to UC16a^TP). Results obtained on carbon isotopes suggest that diagenesis affected and compromised a few carbonate samples in the uppermost 50 m of the section. However, once these samples are discarded, pristine trends suggest that the top of the section records a negative carbon isotope excursion that is interpreted as CMBa-c events that straddle the Campanian–Maastrichtian boundary. This interpretation is supported by the lowermost occurrence of planktic foraminifers Rugoglobigerina scotti and Contusotruncana contusa some 30 m above the base of the negative excursion and 10 m below a positive excursion identified as the Maastrichtian M1+ event. Discrepancies in the stratigraphic range of several planktic foraminifer bioevents are highlighted and advocate for the need of many more integrated records of planktic foraminifer and nannofossil biostratigraphy alongside carbon isotope stratigraphy in the eastern Tethys in order to improve regional and global schemes.     

Potentiality of Paleocene source rocks and their contribution in generating the accumulated oil in the Eocene Pila Spi Reservoir in Taq Taq Oil Field, Kurdistan Region, Iraq

The organic matters within the Paleocene Aaliji and Kolosh Formations in the well TT-04, Taq Taq Oil Field in Kurdistan Region, NE Iraq have been studied optically and also analytically by means of pyrolysis, Gas Chromatography (GC), and Gas Chromatography/Mass Spectrometry (GC/MS). Amorphous organic matters seemed to be the dominant component of the extracted organic matters within the studied section with an obvious increase of the Phytoclasts at the upper part of Kolosh Formation. Thermal Alteration Index, vitrinite reflectance, pyrolysis, and gas chromatography data all indicated the maturity of the lower part from the studied layers (known generally as Aaliji/Kolosh) and within the early stages of oil generation. Oil–source correlation indicates the possibility of contribution of the Paleocene source rocks in generating the accumulated oil in the Eocene Pila Spi reservoir in the field which also appeared to be a mature and of marine-to-mixed carbonate source. Oil–oil correlation between the oil in Pila Spi and the oil in the Upper Cretaceous reservoirs showed the possibility of existence of more than one source for the two oils. GC/MS analysis for the Pila Spi oil indicated the effect of biodegradation which may be considered as one of the reasons for being the American Petroleum Institute (API) of this oil about 24° while the oil in the Cretaceous reservoirs is of more than 47° API.     

Petrography,geochemistry, and provenance of the Chalki rocks in Kurdistan region,North Iraq

Outcrops of the Paleozoic Chalki volcanic rocks are restricted to part of the northern Thrust Zone of Iraq close to Iraqi-Turkish border. Petrographically, the volcanic rocks from the Chalki area are mainly layered, appearing fresh in the field and exhibiting some basaltic lava flows. Porphyritic, amygdaloidal, and microlite-porphyric are the main observed textures. Phenocrysts of primary phases (i.e., olivine, iron oxides) are in a groundmass of feldspars and clinopyroxene. Chalki Formation is intercalated with Pirispiki Formation which consists of thin to medium bedded, greenish gray marl, red mudstone, and veins of calcite. The Chalki rocks are mafic of theolitic basalt type. Geochemically, they have high chromium and nickel concentrations in most samples. Rare earth element (REE) patterns illustrate parallel to sub-parallel, moderately fractionated REE patterns. The low heavy REE (HREE) contents in the studied samples appear to be due to partial melting of metamorphosed oceanic crust leaving HREE-rich accessory minerals (i.e., garnet) as a residual phase in the source. No Eu anomalies were observed in the Chalki samples which may indicate a back-arc basin pattern. The non-subduction signature of the Chalki rocks is confirmed by the Nb/Yb versus Th/Yb diagram, which shows that most of the studied rocks fall in the compositional field of non-arc-related rocks—well within the field of the mid-ocean ridge basalt (MORB)-ocean island basalt (OIB) mantle array.     

Late Cenozoic Deformation Sequence of a Thrust System along the Eastern Margin of Pamir, Northwest China

A thrust belt formed in the basin along the eastern margin of Pamir. The thrust belt is about 50 km wide, extends about 200 km, and includes three compressive structures from south to north: the blind Qipan structural wedge and Qimugen structural wedge, and the exposed Yengisar anticline. The thrust belt displays a right-stepping en echelon pattern. The Qipan structural wedge dies out northward to the west of the Qimugen structural wedge, and the Qimugen structural wedge dies out northward to the west of the Yengisar anticline. Detailed analysis of seismic reflection profiles of the western Tarim Basin reveal that fan-shaped growth strata were deposited in the shallow part of the thrust belt, recording the deformation sequence of the thrust belt. The depth of the Cenozoic growth strata decreases from south to north. The growth strata of the Qipan structural wedge is located in the middle-lower section of the Pliocene Artux Formation (N2a), the growth strata of the Qimugen structural wedge is close to the bottom of the Pleistocene Xiyu Formation (Q1x), and the growth strata of the Yengisar anticline is located in the middle section of the Xiyu Formation (Q1x). Combined with magnetostratigraphic studies in the western Tarim basin, it can be preliminarily inferred that the deformation sequence of the thrust belt along the eastern margin of Pamir is progressively younger northward. The geometry and kinematic evolution of the thrust belt in the eastern margin of Pamir can be compared with previous analogue modeling experiments of transpressional deformation, suggesting that the thrust belt was formed in a transpressional tectonic setting.     

Geochemical and environmental investigation of the water resources of the Tanjero area,Kurdistan region,Iraq

The hydrogeochemistry of groundwater and environmental aspects of the Tanjero area (Sulaimani City, Kurdistan region, Iraq) were investigated statistically. Correlation analysis and cluster analysis revealed several indicators for the source of contaminations. The hydrochemical classification of the water samples determined Ca²⁺, Na⁺, and Mg²⁺ as dominant ions and K/Rb and Na/Cl ratios indicated water–rock interactions with several minerals (e.g., silicate and carbonate minerals). Sr, Ca, Mg, Rb, and K (1757, 117, 29.8, 7.23, and 10.1 μg/L, respectively) in the water samples correlate with each other and show higher concentrations in the wells around scrape and dump sites than the other wells. The water samples were classified according to a redox classification as well, and aerobic and intermediate anaerobic categories were recognized with regard to the reduction of dissolved oxygen and Mn (VI) ions with organic matter in the groundwater. Mn exceeds drinking water standards.     

Serpentinites of the Zermatt-Saas ophiolite complex and their texture evolution

The Zermatt‐Saas serpentinite complex is an integral member of the Penninic ophiolites of the Central Alps and represents the mantle part of the oceanic lithosphere of the Tethys. Metamorphic textures of the serpentinite preserve the complex mineralogical evolution from primary abyssal peridotite through ocean‐floor hydration, subduction‐related high‐pressure overprint, meso‐Alpine greenschist facies metamorphism, and late‐stage hydrothermal alteration. The early ocean floor hydration of the spinel harzburgites is still visible in relic pseudomorphic bastite and locally preserved mesh textures. The primary serpentine minerals were completely replaced by antigorite. The stable assemblage in subduction‐related mylonitic serpentinites is antigorite–olivine–magnetite ± diopside. The mid‐Tertiary greenschist facies overprint is characterized by minor antigorite recrystallization. Textural and mineral composition data of this study prove that the hydrated mineral assemblages remained stable during high‐pressure metamorphism of up to 2.5 GPa and 650 °C. The Zermatt‐Saas serpentinites thus provide a well documented example for the lack of dehydration of a mantle fragment during subduction to 75 km depth.     

Geochemistry and geodynamics of the Mawat mafic complex in the Zagros Suture zone, northeast Iraq

The Iraqi Zagros Orogenic Belt includes two separate ophiolite belts, which extend along a northwest-southeast trend near the Iranian border. The outer belt shows ophiolite sequences and originated in the oceanic ridge or supra-subduction zone. The inner belt includes the Mawat complex, which is parallel to the outer belt and is separated by the Biston Avoraman block. The Mawat complex with zoning structures includes sedimentary rocks with mafic interbedded lava and tuff, and thick mafic and ultramafic rocks. This complex does not show a typical ophiolite sequences such as those in Penjween and Bulfat. The Mawat complex shows evidence of dynamic deformation during the Late Cretaceous. Geochemical data suggest that basic rocks have high MgO and are significantly depleted in LREE relative to HREE. In addition they show positive ? _Nd values (+5 to+8) and low 87Sr/86Sr ratios. The occurrence of some OIB type rocks, high Mg basaltic rocks and some intermediate compositions between these two indicate the evolution of the Mawat complex from primary and depleted source mantle. The absence of a typical ophiolite sequence and the presence of good compatibility of the source magma with magma extracted from the mantle plume suggests that a mantle plume from the D″ layer is more consistent as the source of this complex than the oceanic ridge or supra-subduction zone settings. Based on our proposed model the Mawat basin represents an extensional basin formed during the Late Paleozoic to younger along the Arabian passive margin oriented parallel to the Neo-Tethys oceanic ridge or spreading center. The Mawat extensional basin formed without creation of new oceanic basement. During the extension, huge volumes of mafic lava were intruded into this basin. This basin was squeezed between the Arabian Plate and Biston Avoraman block during the Late Cretaceous.     

Indicating the Possibility of Activation of Large and Old Landslides and Risk Estimation Using Remote Sensing and Field Data,Examples from the Iraqi Kurdistan Region,Iraq

Geotectonics - Majority of the Iraqi Kurdistan Region is a mountainous area with relief differences that attain up to 1000 m, and locally more. The presence of dense net of rivers, streams and...     

Evolution of the Meyeri Thrust Zone of the Northern Ladoga Region (Republic of Karelia,Northwest Russia): PT Conditions for the Formation of Mineral Parageneses and Geodynamic Reconstructions

Geotectonics - In our study we characterize the thermodynamic regimes in the thrust zone of the newly formed Paleoproterozoic continental crust of the Svecofennian mobile belt on the outskirts of...     

Quantitative finite strain and kinematic flow analyses along the Zagros transpression zone, Iran

The Ghouri area in southwest Iran exposes a cross section through the Zagros orogenic belt. The area provides an opportunity to investigate quantitative finite strain (Rs), kinematic vorticity number (W_k), proportions of pure shear and simple shear components, sense of shear indicators, steeply plunging lineations, and other moderate to steeply plunging stretching lineations in a transpressional zone. Based on a classical strain analysis of deformed microfossils with oblate strain ellipsoid shape, the Zagros orogenic belt is classified as a pure-shear dominated zone of transpression, but asymmetry of shear-sense indicators suggests that a significant component of simple shear was involved along the deformation zone boundaries. The long axes of the microfossils and stretched pebbles of a deformed conglomerate were used to indicate the stretching direction in this zone. The stretching lineations have a steep to moderate plunge but a constant strain magnitude. Characteristics of dextral inclined transpressional kinematics in the Zagros continental collision zone were quantified and indicate an estimated k-value < 1, an angle between the maximum horizontal axis of the instantaneous strain ellipsoid and the zone boundary (θ = 32°), asymmetrical dextral shear-sense indicators, and an angle of relative plate motion (α = 25°).     

Vitrinite reflectance as a tool for determining level of thermal maturity for the Upper Jurassic Naokelekan and Barsarin Formations in Sargelu location,Kurdistan Region,NE Iraq

Ten samples from the Upper Jurassic Naokelekan and Barsarin Formations in an outcrop section near Sargelu Village were studied to evaluate their thermal maturity using vitrinite reflectance method. The studied beds appeared to be mature and within the oil generation window (0.79–1.25 % vitrinite reflectance in immersion oil (Ro)). Some of the reflectance histograms showed bimodal distribution indicating existence of nonindigenous populations which were all ignored during the measurements of the mean value of Ro. Comparison between the results obtained from vitrinite reflectance method and some other methods like pyrolysis and gas chromatography showed variations which finally more reality believed to be for the vitrinite reflectance method.