Zagros Foreland Basin Research Articles

Potential Field Imaging of Salt and Basement Structures in the Southern Zagros Foreland Basin

Potential Field Imaging of Salt and Basement Structures in the Southern Zagros Foreland Basin

Basin Analysis and Paleogeography of the Zagros Foreland Basin during the Maastrichtian, High Zagros Basin, Iran

Basin Analysis and Paleogeography of the Zagros Foreland Basin during the Maastrichtian, High Zagros Basin, Iran

The Paleogene Forebulge Carbonate Banks, Zagros Foreland Basin, Northern Iraq: their Paleogeography, Basin Evolution, and Economic Implications

The Paleogene sequence of Zagros foreland basin NE Iraq during the Late Paleocene- Middle Eocene is punctuated by linear and disconnected chains of carbonate bank-ramp associations. These carbonate units had developed over the NW-SE trending Paleogene basin forebuldge. Discussion of origin, facies type, and stratigraphic architecture of these banks and associated facies was fully covered by the first part of this research project. In this part the chronostratigraphic synthases of the sequence, the paleogeography, and basin evolution is examined as an integral part of the investigation of the evolution of the Paleogene Zagros foreland basin. Research methods include regional stratigraphic correlation, and biostratigraphic data compilation to infer the chronostratigraphic sequence of the events. The paleogeographic facies mapping and basin history are reviewed accordingly. Research data are collected from 15 master surface sections. In addition to the re-examination and re-interpretation of 40 previously studied surface and subsurface well logs, which are compiled for basin-wide study and regional paleogeographic mapping. The analysis of the compiled biostratigraphic data shows that the inferred age of the associated stratigraphic units is as follows: Sinjar Formation. (E. Thanetian – L. Ypresian), Khurmala Formation (Ypresian - E. Lutetian), Kolosh Formation (Daian -Thanetian), and Aaliji Formation (Danian - Ypresian). Based on this chronostratigraphic synthesis, the basin forebulge history during the Paleogene period is divided into 5 stages: the Pre-bank, Early Bank Development, Bank-ramp Development, Back-bank Lagoon, and Lagoonal dolomitization stage. The paleogeography and paleofacies maps of each stage is discussed in terms of the basin forebulge evolution. An alternative hydrocarbon play of the forebulge-controlled Paleogene sequence is discussed, with a case study from the Sufaiyah oil field of northwest Iraq.

Tectonic framework of Iraq. A critical review and discussion

The Iraqi territory forms the northeastern part of the Arabian Plate, which is in collision with the Eurasian Plate. The collision of the plates has formed the Zagros Foreland Basin, which includes the Zagros Fold–Thrust Belt. The belt covers the majority of the northern part of Iraq (Kurdistan Region of Iraq) and parts of the central part of Iraq. South of the belt, the Mesopotamian Foredeep is developed. All these parts of Iraq are considered tectonically unstable. To the west and south of the Mesopotamian Foredeep, the tectonically stable part is developed that has been affected by a lesser amount of deformation as compared to the remaining unstable parts by the exerted forces related to the collision of both plates. All researchers have divided tectonically Iraq into two main tectonic domains; called Stable and Unstable shelves, which are further divided into zones and sub-zones. However, different terms and names were used by different researchers, which has confused readers and workers who have dealt with the tectonics of the Iraqi territory. We have reviewed and discussed all existing divisions by different researchers and have suggested new terminology using the existing maps, reports, scientific published articles, and interpreting satellite images, besides field observations. Moreover, we presented a tectonic map with the suggested new terminology.

The Paleogene Carbonate Banks of the Zagros Foreland Basin’s Forebulge, Northern Iraq: Stratigraphic Architectures and Facies Associations

The Paleogene sequence of the Zagros foreland basin of NE Arabiais punctuated by a linear chain of carbonate bank-ramp associations. These carbonate banks had developed over the NW-SE trending basin forebulge. Continued convergence and compressional tectonics of the basin made the forebulge become incipient and shallow enough to commence carbonate sedimentation. The porpose of this work is to investigate the origin, facies and regional stratigraphic relations of these carbonates to the forebulge and other basin depozones. Stratigraphic data of this research are collected from (15), measured outcrop sections distributed over the basin forebulge zone and surroundings. In addition, re-examination and reinterpretation of (30) previously studied surface and subsurface sections are compiled into the study. This done to integrate the regional facies distribution and basin-wide sequence stratigraphic architecture. Stratigraphic investigations include lithostratigraphic logging and correlation, microfacies analysis, and facies modeling. Four major banks were recognized, three of these banks (informally named: Dohuk, Kirkuk, and Sulaimaniyah) were developed over the forebulge zone. The other one (Sinjar bank) of the Sinjar area, is related to basininversion mechanism. The forebulge carbonate banks were developed as the reefal limestone of the Sinjar Formation, and the lagoonal carbonate and shale of the Khurmala Formation. The Sinjar Formation is dominated by coralgal reef and foraminiferal-shoals with facies spectrum forming the basic body of the bank. The ramp setting was developed on both sides of the bank. The bank limestone represents the inner ramp facies, whilea windward ramp is developed as foraminiferal bioclastic limestone fingers into the back-bulge basinal marlstone of the Aaliji Formation. A leeward ramp facies was developed into the foredeep depozone, with bioclastic carbonate intercalations that characterize the upper part of the Kolosh Formation. At a later stage of basin shoaling (Early Eocene), a carbonate back-bank lagoon was developed over the foredeep area. It became gradually, isolated at certain parts of the basin, and finally replaced by the dolostone of the Khurmala Formation.

Problemy ophiolitów Zagros i ciał bazaltowych, przykłady z Regionu Kurdystanu, północny Irak

In the Iraqi Zagros, there are ten ophiolites and basaltic bodies, the famous ones are Penjween, Mawat, Bulfat and Peshashan Ophiolite complexes in addition to basaltic bodies such as Kata Rash, Avroman, Gercus, Chalki, and Hamrin basaltic bodies. The present study describes more than 12 significant problems concerning the previous assigning of the bodies as igneous rocks. These problems are observable in the field, laboratory, and in most previous works of literature that oppose the magmatic origin of these bodies. Our study explicated all aspects of each problem and clarified how the problems contradict magmatic crystallization and aid the sedimentary origin of these claimed igneous bodies. Finally, the interpretations of all the problems were collected as conjugate pieces of evidence for appraisal of the new origin of all igneous bodies in the Iraqi and Iranian Zagros belt. The outcomes consider the ophiolitic and basaltic rocks metamorphosed volcaniclastic sandstones (greywackes or mafic sandstone). These sandstones belong to fresh or metamorphosed greywackes of stratigraphic units of the Paleocene-Eocene Walash Formation (as distal facies) and Kata Rash Conglomerate (as proximal facies) which were previously considered volcanic rocks. These sediments are sourced originally from Urumeiah-Dokhtur Magmatic Arc (ADMA) and deposited inside Neo-Tethys, present Sanandaji-Sirjan Zone (SSZ), during the Jurassic-Early Cretaceous. Later, the sediments were metamorphosed and uplifted during the Paleocene and deposited inside the Iraqi Zagros belt by turbidity currents inside the Zagros Foreland basin. These ideas are shown in detail by tectonic and paleogeographic models.

Biostratigraphy of the Upper Cretaceous Gurpi Formation: Enhancing correlation potential by identification of abundance events of planktonic foraminifera as auxiliary indicators

The Upper Cretaceous Gurpi Formation represents a pelagic interval composed of shale and marly limestone rich in planktonic foraminifera. This study focuses on the analysis of planktonic foraminifera from the Gurpi Formation in the Zard-Shehneh Anticline section in southwestern Iran. The formation is of significant importance in parts of the Zagros foreland basin, as it acts as both a cap rock and a source rock. The presence of the Cretaceous/Paleogene (K/Pg) boundary at the upper boundary of this formation further emphasizes the significance of studying it. Therefore, the study of its biozonation and bioevents is crucial. Through the recovery of planktonic foraminifera from 125 samples in thin sections and washed residues, 30 genera, 88 species, and 10 biozones were identified for the Gurpi Formation, as well as 7 genera, 12 species, and one biozone for the base of the overlying Pabdeh Formation. In addition, high accuracy was achieved in the placement of bioevents, including: 1) the occurrence of Globotruncana linneiana at the base of the Gurpi Formation, indicating the Santonian age; 2) the highest occurrences of Dicarinella asymetrica and most species of marginotruncanids, marking the Santonian/Campanian boundary; 3) the earlier occurrence of Globotruncana aegyptiaca; 4) the occurrence of the Campanian/Maastrichtian boundary in the lower part of Gansserina gansseri Zone; 5) the occurrences of five abundance events including: V. eggeri in the upper half of the Dicarinella asymetrica Zone, benthic foraminifera in the middle to upper half of the Radotruncana calcarata Zone, G. linneiana, G. lapparenti, and G. esnehensis in the lower part of Globotruncana falsostuarti Zone, G. esnehensis in the upper part of Globotruncana falsostuarti Zone, and G. gansseri at the end of the Pseudoguembelina hariaensis Zone; and 6) the disappearance of most keeled planktonic foraminifera species during the late Maastrichtian, starting from the middle parts of the Abathomphalus mayaroensis Zone. In this study, the K/Pg boundary, which is considered the upper boundary of the Gurpi Formation, exhibits unconformity and condensation. The high-resolution biozonation and bioevents framework not only allows for accurate dating of the Gurpi Formation in the Zard-Shehneh section, but also enhances the ability to precisely correlate sedimentary sequences and paleoenvironmental intervals at regional or global scales in future studies.

Article Review/ The Tectonic Evolution of Erbil Area (Ne Iraq) as a Part of the Northeastern Margin of the Arabian-Nubian Plate Throughout Albian-Early Eocene

The Albian-Early Eocene tectonic evolution of the Zagros Foreland Basin of the High Folded Zone in the Iraqi Kurdistan region has been studied based on the recent foreland basin system concept. This study showed that during the cretaceous (Albian – Cenomanian) there was a geodynamic shift from a passive margin to a foreland basin system phase, not to an active margin phase as mentioned in the previous studies. The advance of the continental margin of the Arabian-Nubian Plate (ANP) toward the subduction zone imposed a tectonic load leading to the form of a flexural wave. The consequences of the last tectonic event were reflected by the continuous deposition of the Balambo Formation. in a foredeep depozone. This happened concomitantly with a flexural emergence of the continental shelf further to the west forming a forebulge depozone represented by the deposition of reefal facies of the Qamchuqa Formation. These geodynamic changes are considered here to represent the Megasequence boundary between the Tectonic Megasequence (TMS) of AP8 and AP9. The last sequence of the passive margin was the Qamchuqa Formation Which is called the Pre-Orogenic Carbonate Platform and was separated from the Bekhme Formation by regional unconformity (Megasequence boundary). The latter is represented by the Lower Sequence of the foreland basin system, which is called the Syn-Orogenic Carbonate Platform (SCP). During the Middle Campanian, the Zagros foreland basin started with the underfilled stage, and it was entirely clear by the end of the Cretaceous comprising a broad threefold subdivision of depositional realms that translated into three stratigraphic units known as trinity underfilled units of foreland basin system. The lower carbonate unit, the pelagic and hemipelagic unit, and the upper flysch clastic unit are represented by Bekhme, Shiranish, and Tanjero Formations respectively. All of these units were superimposed during basin depocenter migration and became younger toward the southwest in front of progressing the orogenic wedge toward the Arabian Craton. During the late Maastrichtian to Paleocene – Early Eocene, the Zagros foreland basin underwent a transition from underfill to fill the stage. Deep exhumation of the orogenic wedge and ophiolite assemblage had supplied the clastic sediment of the Kolosh Formation into the basin covering the foredeep and most of the forebulge and backbulge depozones.

Stratigraphic Sequence and Diagenetic Effects of the Upper Qamchuqa Formation in Khabaz and Kirkuk Oil Fields, Northern Iraq

The Upper Qamchuqa Formation was deposited in Zagros foreland basin in the north of Iraq during the Late Albian age. Two boreholes from Kirkuk oil field (K-229) and Khabaz oil field (Kz-4) are selected in the current study, where 100 samples of cores and cutting were used to determine diagenetic evolution of the Upper Qamchuqa Formation. Five major sub-environments can be diagnosed within the Upper Qamchuqa sequence, they are: shallow-open marine environment, semi-restricted marine environment, restricted marine environment, shoal and deep outer ramp environment. The diagenesis process are contain the physical or chemical variations in sedimentary rocks and sediments that happen after the deposition, where many diagenetic process effect on the Upper Qamchuqa Formation which are: Micritization, Cementation with three types (blocky, drusy,and syntaxial calcite overgrowth cement ), Dolomitization with three types too (scattered, Pervasive coarsely ,and saddle dolomite), neomorphism, recrystallization, silicification, dissolution and compaction (mechanical and chemical). There are four sedimentary cycles: cycle A extends from the upper part of the underlying Upper Sarmord Formation (TST) to the shallow open marine facies (HST) of the lower part of Lower Qamchuqa in k-229 which ended with shoal facies, cycle B on the other hand, shows a grain dominated facies where the carbonates buildup kept pace with the still relative sea level (keep up) during high stand which deposited under semi-restricted and restricted successively, cycle C shows a marked variation in thickness within the sections (K-229 and Kz-4); it is greatest thickness was noticed at k-229 where its lower part is mostly mud dominated in Kz-4, and cycle D shows a distinct variation in facies change from grain-rich to mud-poor lithology of restricted to semi-restricted facies in the East (k-229) to predominantly restricted marine conditions at the central area (Kz-4).

Litho- and biostratigraphy of the early Eocenelarger benthic foraminifera-dominated carbonates of the central Tethys domain, Zagros Foreland Basin, SW Iran

The Early Paleogene Tethyan domain saw the development of large platform carbonates rich in large benthic foraminifera (LBF), of which the Taleh Zang Formation in Lurestan Basin, SW Iran, represents an excellent example. The LBF assemblage is dominated by alveolinids, together with a variety of foraminiferal genera such as Nummulites, Rotalia, Sackesaria, Assilina, Operculina, and Glomalveolina. Smaller benthic foraminifera, calcareous algae, gastropods, echinoids, and bivalves constitute minor components of the carbonate. Biostratigraphy analysis of the LBF is conducted on two distinct sections of the Taleh Zang Fm. The sections referred to as TZ-1 and TZ-2 have respective thicknesses of 87 m and 132 m. This analysis has constrained the formation age to the early Ypresian within Shallow Benthic Zones (SBZs) 5–7. Facies analysis supports the major accumulation of these successions in a shallow water environment within the euphotic zone. We recognize 9 distinct facies and microfacies representing four main depositional environments including tidal flat, lagoon, bioclastic shoal, and shallow open marine. These environments are distributed along a low-angle homoclinal ramp and form the foundation of a stratigraphic interpretation characterized by intervals displaying shallowing and deepening trends. Three shallowing-upward intervals have been identified within the Taleh Zang succession. The determined intervals cannot be solely attributed to global sea level fluctuations and support a significant impact of the regional structural context resulting from collision-induced uplift and variable subsidence rates. The identified intervals exhibit local and regional correlation and compatibility on the Arabian Plate, providing robust confirmation of the significant roles played by both tectonics and eustasy at a regional scale.

Lower Eocene carbonate ramp clinoforms of the southern Tethys; Zagros Foreland Basin, SW Iran: Sequence stratigraphy architecture, basin physiography and carbonate factory controlling parameters

AbstractExcellent cliff exposures in the Khush‐Ab and Chenareh anticlines (Zagros Foreland Basin, SW Iran) offer a good opportunity to document stratal geometries, paleofacies heterogeneity, depositional architecture and depositional cycles of the Lower Eocene sedimentary basin system. These unique outcrops containing six logged sections have been studied across a large‐scale transect, covering ca. 10 km of continental (Kashkan Formation), carbonate‐dominated platforms (Taleh‐Zang Formation) and submarine fan to basin‐floor settings (Amiran and Pabdeh formations). Field observations of the bedding geometries revealed a set of NE–SW oriented carbonate ramp clinoforms (clinoformal units 1–4) with sigmoidal cross‐sectional shapes and an internal fore‐stepping architecture. Based on detailed facies analysis, six facies associations (FA) were identified (FA.I to FA.VI), which are interpreted to have been deposited laterally in the continental, proximal to distal and deep‐water settings of a distally steepened carbonate ramp. According to the stratal stacking pattern, bounding surface, facies architecture and internal makeup of carbonate clinoforms, four H‐F‐cycles (cycle I–IV) corresponding to a lower hierarchical rank (fourth‐order cycle) were recognized and nested within the regressive stacking pattern (HST) of a higher hierarchical rank (third‐order sequence). These H‐F‐cycles are arranged in three segments (bottomset, foreset and topset) of each clinoformal unit. Higher rank transgressive blocks (TST) discriminated each clinoformal unit by up‐deepening sets of the H‐F‐cycle V. In total, five third‐order depositional sequences were identified. The sequence, stratigraphic framework and internal makeup of this carbonate platform indicate that these carbonate sloping successions are the type of accretionary carbonate ramp clinoforms that display an ascending ramp‐slope break trajectory. Evolutionary episodes of biogenic communities, climatic change, local tectonic movements, physical processes (e.g. waves and storms) and water depth gradient are major forcing parameters that controlled the carbonate factory and depositional geometry of this Lower Eocene succession; however, carbonate‐producing organisms and eustatic sea‐level fluctuations played the first role, and local tectonic movements in response to tectonic activities of the Zagros Foreland Basin played the second role. As a result, Taleh‐Zang carbonate platforms are rich in diverse assemblages of LBFs without fragments of coral and red algae, which appear to be a consequence of a hothouse state that diminishes the global thermal gradient, weakens pycnoclines and thereby limits the turbulence.

Emphasizing Lithostratigraphic Rules In Distinction Of Formal Units: Sinjar Vs Khurmala Formations, Case Study

Recognition, identification, and correlation of formal lithostratigraphic units should always follow the rules of the definition of lithostratigraphic units established in the Stratigraphic Code of Nomenclature, set by the International Stratigraphic Commission. This case study is attempting at elaborating on this argument by discussing the identification and differentiation between the Sinjar and Khurmala formations in outcrop and well sections. Stratigraphic data for this study were compiled basin-wide, with nearly fifty localities of both formations from the Zagros foreland basin of Kurdistan in NE Iraq. Examinations include a review of microfacies documentation, Facies reinterpretation as well as sequence analysis. The Sinjar and Khurmala formations are carbonate units developed during the final filling stage of the Zagros foreland basin of northeast Iraq. The Sinjar Formation is characterized by shallow marine coralgal-foraminiferal limestone of reefal, lagoonal, shoal, and overall ramp setting. Other lithologies such as dolomitic limestone or marly limestone are minor and secondary. The Khurmala Formation, on the other hand, is dominated by thick beds of dolostone with secondary lithologies including recrystallized limestone and dolomitic limestone and marly limestone. Microfacies analysis of the Khurmala Formation reveals that it represents a lagoonal lithofacies equivalent to the lagoonal facies of the Sinjar Formation but intensively dolomitized at specific areas of the basin. This close relationship between the two formations, leading in some cases to mixing between both lithologies or rather confusion and misidentification. The best way of differentiating between the two units is by adhering to the lithostratigraphic rules and principles of the formal stratigraphic description, which emphasize the formal lithostratigraphic description of each formation.

Microfacies correlation, analysis and palaeoecological reconstruction of Rupelian–Aquitanian succession in the central part of Lorestan Province, Northwestern Iran

The Oligocene–Miocene Asmari Formation is a sequence of shallow-water carbonate carbonates in the Zagros Basin. This formation is a significant oil reservoir that was formed in the Zagros foreland basin in southwestern Iran. The Razan section, located in the northwest of Zagros in the Lorestan province, was investigated to study microfacies types and evaluate the sedimentary environment. This section was then compared with the MakhmalKuh and Dehloran sections. It comprises limestone units with thin to medium strata, sometimes thick-bedded limestone, and other skeletal and non-skeletal components. Based on the biostratigraphy studies, 24 foraminifer genera and species have been identified. Among the foraminifera, the species of Peneroplis farsensis, Peneroplis evolutus, Austrotrilina howchini, Austrotrilina asmarensis, Dendritinarangi, Quinqueloculina sp., Triloculina trigonula, Pyrgo sp., Polymorphinids, Spiroluculina sp. and Meandropsina anahensis are the most important specimens. Based on identified co-occurrence taxa, the Austrotrilina howchini–Peneroplis evolutus assemblage zone has been recognised in the study area, which indicates early Miocene (Aquitanian). Texture analysis and faunal assemblages led to the recognition of fourteen microfacies. Based on the petrographic analysis, five depositional settings were determined in the studied section: (a) the outer ramp settings dominated by pelagic foraminifera, bryozoan, echinoid and benthic foraminifera such as Nummulites, Rotalia, Dendritina and Meandropesina iranica as a proxy for relatively deep marine conditions; (b) the mid ramp, characterised by sizeable perforate foraminifera such as Amphistegina, Operculina, Heterostegina and planktonic foraminifera; (c) the barrier, marginal marine environment dominated by foraminifera such as Miogypsinoides sp., Peneroplis, Meandropsina, Dendritina and Neoalveolina, as well as peloid and corallinacean algae; (d) the lagoon dominated by benthic foraminifera Austrotrillina, Dendritina, Peneroplis, Miogypsinoides, Borelis, Archaias, miliolids and red algae and (e) the tidal flat, the shallowest part of the inner ramp, dominated by fenestral dolo-mudstone without any fossils. The faunal assemblages represent warm tropical waters under euphotic and mesophotic conditions in a homoclinal ramp.

Meteoric Water Incursion, Crude Oil Degradation and Calcite Cementation of an Upper Cretaceous Reservoir in the Zagros Foreland Basin (Kurdistan Region of Iraq)

Field observations, together with the results of gas chromatography–mass spectrometry (GC-MS) and stable carbon isotope analysis of bitumen, coupled with fluid inclusion microthermometry and stable isotope analyses of closely associated vug- and fracture-filling columnar calcite in the Upper Cretaceous Bekhme Formation, Kurdistan Region of Iraq, suggest that the degradation of crude oil was caused by the regional incursion of meteoric waters. This incursion, which is interpreted to have occurred during tectonic uplift during the Zagros Orogeny, is evidenced by: (i) the depletion of n-alkanes and acyclic isoprenoid alkanes (pristane and phytane) in the bitumen; (ii) low δ13CVPDB values (−8.5‰ to −3.9‰) and δ18OVPDB values (−22.9‰ to −15.0‰), with more radiogenic Sr isotopic ratios (0.70771–0.70772) compared to Cretaceous seawater; and (iii) low salinity and low temperatures (20 to 40 °C) in fluid inclusions of the columnar calcite. This study demonstrates that regional meteoric water incursion into sedimentary basins can be linked to crude oil degradation accompanied by calcite cementation events in carbonate reservoirs.

Early-middle Miocene Inversion of the Abu Jir Fault in the Western Iraq: a Possible Consequence of the Arabian Plate Northward Movement

The Abu Jir fault zone in western Iraq that marks the western limit of the Zagros foreland basin merges with the Anah graben in the north. The northern segment of the Abu Jir fault zone and the western Anah graben are inverted structures. In this study, we investigated the timing and mechanism of the northern Abu Jir fault zone inversion in comparison with other inverted structures like Tel Hajar and Sinjar, which are located in the north and closer to Arabia–Eurasia collision zone. In the study area the Abu Jir fault zone is characterized by a local-scale northwestern-trending asymmetric fold, associated with inverted normal faults, positive flower structures, right–lateral strike-slip faults, and seismically induced early middle Miocene slump structures. Based on the structural synthesis of the surface geology and age constraints from syntectonic deposits at the northern Abu Jir fault area, the Abu Jir fault inversion and its western block northward movement were inferred to be resulted from forces that originated from the south to the north, unlike the northern younger inverted structures. This early middle Miocene age of the Abu Jir fault inversion is comparable to the arrival time of the Afar plume hot mantle material flow from the south to the north in western Arabia. Therefore, we argue that the Abu-Jir fault inversion is more likely to be due to dragging of the Arabian plate by mantle flow from the south to the north rather than shortening propagation from the north to the south.

Geology of recently recognized lithologies inside the Red Bed Series in the Chwarta-Mawat area, Kurdistan Region, NE-Iraq

The sequence of the coastal siliciclastic facies of the Paleocene-Eocene Zagros Foreland Basin is well exposed in the Chwarta-Mawat area, north of Sulaimani Governorate, northeastern Iraq. According to previous studies, this sequence is designated as Red Beds Series (RBS), consisting of more than 2000 m of fine and coarse red and grey clastics. The present study found recently recognized lithologies (RRLs) about 100 thick inside the series and encompassed green marlstone with subsidiary detrital limestone which has significant tectonic and paleogeographic results. The petrography, biostratigraphy, and boundary conditions studies are applied to uncover their origin. The new lithologies are deposited in the subsiding basin in the Imbricate Zone during the Middle Eocene. During this age, the Tertiary Foreland Basin was separated by a paleohigh into two basins, (northern and southern basins). In the northern basin, the RRLs have deposited as deep facies of the Naopurdan Formation while in the southern basin the Pila Spi Formation was deposited as lagoonal facies. The former formation was deposited as reefal facies in the shelf area of the northern basin to the northeast Chawrta and Mawat Towns. The RRLs, units one and two of the series (in the Thrust Zone) are correlated respectively with Pila Spi, Sinjar and Gercus formations in the High Folded Zone. These correlations are shown on the stratigraphic columns and paleogeographic models with the aid of nannofossil and benthonic foraminiferal studies. This study is the most important step for solving the tectonic and paleogeographic setting of northeastern Iraq and for a better understanding of the Zagros Collisional belt.

Petrography and Clay Mineral Variations Across the Cretaceous/Paleogene (K/Pg) Boundary, Sulaimani, Kurdistan Region, Iraq

The Cretaceous/Paleogene (K/Pg) boundary marks the global extinction of many life forms, this boundary around Sulaimani city coincides with the boundary between Tanjero and Kolosh formations. These two units are flysch deposits of the Zagros Foreland Basin. This study focuses on petrography and clay mineralogy variations between these two units. Petrographic study, X-Ray Diffraction analysis, and Scanning Electron Microscope analysis were conducted on samples from different lithologies. The petrographic study of fine-grain lithologies shows that they are mainly wackestone without variation across the boundary. Sandstone petrography shows variation in framework components by increasing quartz, feldspar, and igneous fragments while argillaceous, carbonates, chert, and chalcedony fragments are decreased from Tanjero to Kolosh formations. Obtained results from XRD and SEM show that the clay mineral assemblage is dominated by corrensite (regularly interstratified chlorite/smectite) with discrete chlorite, smectite and traces of illite. The existence of these clay assemblage suggests that corrensite is the diagenetic product of smectite as it is an intermediate stage of smectite chloritization. Enrichment of precursor smectite and high content of unstable grains in sandstones across the K/Pg boundary is the result of low-intensity weathering in arid and seasonal climates of the source area. The smaller size of detrital smectite than other clay minerals is behind its enrichment in the deep marine basin for both Tanjero and Kolosh formations. Sandstone enrichment with sedimentary fragments in both formations related to uplifted sedimentary terrain in its hinterland, while variation across the boundary indicates gradual uplift of Zagros ophiolite zone in the early Paleogene.

Biostratigraphy and paleoenvironmental significance of Paleogene foraminiferal assemblages from Dashte Zari area in High Zagros, West Iran

The Paleogene carbonate deposits of Pabdeh and Jahrum formations are widespread from the northwest (Dashte Zari area) to the southwest of the Shahrekord region in the High Zagros Mountains of Iran and record the lateral and upward transition from open marine into the shallow water environment. The Pabdeh Formation shows a succession of open marine pelagic and hemipelagic limestone, argillaceous limestone, and argillaceous chert. It consists of planktonic wackestone, pellet-planktonic wackestone, mudstone with planktonic foraminifera, and radiolarian siliceous wackestone, which accumulated within the Zagros Foreland Basin. The planktonic foraminifers are assigned to the Late Paleocene–Late Eocene and correspond to subtropical and tropical Zones P4b–E15. The Jahrum Formation is represented by bioclast-bearing limestone and calcarenite. It consists of benthic foraminiferal wackestone, benthic foraminiferal-red algal packstone, and bioclast-intraclast packstone deposited in a shallow platform environment. The Jahrum Formation is inter-fingered in the upper part of the Pabdeh Formation and finally overlies it conformably during the Bartonian–Priabonian. Shallowing and off-lap relationships record basin shrinking, while repeated inter-fingering signals moderate tectonic subsidence. Both formations are disconformably covered by the Late Oligocene–Miocene Asmari Formation. Keywords: biostratigraphy, Pabdeh Formation, Zagros, Paleogene, Iran.

Stratigraphy and Basin Development of the Oligocene-Early Miocene Succession, Southeastern Iraq

The study area is situated in the northern part of the Arabian Plate. The evolution of the Zagros Foreland basin is related to the compressional tectonic system at the beginning of the Tertiary Period. This study gives an adequate nomenclature for the Oligocene – Early Miocene Sequence is Missan Group. The Buzurgan Oilfield was chosen to represent the stratigraphic column corresponding to that period. These sediments were subdivided into two cycles, where each one ends by a sequence boundary, equivalent to the lowstand siliciclastic residues in the basin center. The first cycle, Paleocene-Oligocene Epoch, was deposited marly limestone with planktonic foraminifera in the basin center during the transgressive and highstand conditions. The Lower Missan Group was deposited during the latest Oligocene lowstand conditions and overlaid the deep marine Oligocene sediments. The second cycle represented the Early Miocene Epoch (Aquitanian), by which the Euphrates Formation was deposited during the transgressive and highstand conditions and ended by the lowstand conditions sediments in the basin center as an Upper Missan Sandstone Member. These two cycles are conformably bounded by Lower Miocene (Jeribe Formation) and Oligocene (Tarjil Formation).

Influence of the Tectonic Activity on the Terraces of the Greater Zab River, NE Iraq, Zagros Fold-Thrust Belt

The study area lies in the Lower Folded Zone of the Outer Platform of Iraq, which belongs to the Arabian Plate. The Outer Platform is a part of the Zagros Fold-Thrust Belt, which is in the Zagros Foreland Basin. Due to the collision of the Arabian and Eurasian plates, tens of folds were developed among the anticlines that occur in the study area. The course of the Greater Zab River in the study area crosses several anticlines before merging with the Tigris River. Different river terrace levels were recognized locally as three levels along the course of the river. It is clear from the achieved data that the rates of an incision during the Early, Middle and Late Pleistocene are: 5.036 mm/ 100 years, 8.979 mm/ 100 years, and 18.117 mm/ 100 years, respectively. The maximum rate of upward movements (3.485 mm/ 100 year) was recorded at 700 m from Bekhme gorge, where the first exposures of the Fatha and Injana formations exist. The maximum rate of downwards movement (13.769 mm / 100 year) was recognized at the southeastern part of Barda Rash anticline. The rate of the upwards movement decreases towards the southeast, and the minimum rate of downwards (7.314 mm / 100 year) was recorded in Sarta oil well 1 location, near the Greater Zab River. The rates of the upwards and downwards movements are not regular. This is attributed to the existence of anticlines and synclines, which means Neotectonic activities.