Western Desert Research Articles

Retraction Note: Petrophysical characterization and durability aspects of tufa rocks at Kurkur Oasis, Western Desert, Egypt

Retraction Note: Petrophysical characterization and durability aspects of tufa rocks at Kurkur Oasis, Western Desert, Egypt

3D Reservoir modelling for Sidi AbdelRahman oil field, Alamein basin, Western Desert, Egypt

3D Reservoir modelling for Sidi AbdelRahman oil field, Alamein basin, Western Desert, Egypt

Exploring carbonate reservoirs potential, north Egypt

Carbonate reservoirs contain a significant portion of the world's oil reserves. The Middle East is home to many of these reservoirs. Carbonate reservoirs can be found in a few very large oil fields, including Egypt's Zohr field, the largest conventional gas field in Egypt. In this article, we present a couple of successful tertiary carbonate reservoirs that are bearing hydrocarbon in the Egyptian Western Desert and Gulf of Suez provinces, they are distributed across Egypt's subsurface, and they are characterized by heterogeneous porosity and permeability. These heterogeneities are caused by the wide spectrum of tectonostratigraphic environments in which carbonates are deposited and by subsequent diagenetic alteration of the original rock fabric. The structural analysis of the study areas based on the interpretation of both geophysical and geological data, in JD, Abu Sennan, and the North Amer areas in the Western Desert and offshore Gulf of Suez respectively showed that tectonostratigraphic history during tertiary time affected a great extent carbonate reservoir quality. Major fault trends formed secondary fracture porosity possibly allowing hydrothermal solutions to pass through the reservoirs and form secondary vuggy porosity. These characteristics are considered important factors of promising carbonate reservoirs. In this study, several carbonate reservoirs have been outlined. The study workflow helped us better identify carbonate prospects with high fractured density.

Late Mesozoic–Cenozoic geoheritage resources of the Kharga Oasis (Egypt): Novel assessment, exploitation perspectives, and policy implications

Geoheritage resources are valuable to countries and regions, which make urgent their exploration. Particularly, Egyptian geoheritage has been examined only partly, and it has not been reported from many areas. New field investigations in the Kharga Oasis in the southern Western Desert of Egypt permit to report a new portion of geoheritage resources. The collected materials are used to propose six geosites, describe them (particularly, standardized geoheritage types are established), and assess semi-quantitatively. The approach is the same as already used for some other areas of Egypt, and the semi-quantitative assessment is based on scoring of various geosite properties with the different weight. It is established that these geosites exhibit lithologies and depositional environments of Upper Cretaceous–Eocene terrestrial and marine sedimentary rocks, Quaternary terrestrial carbonates (tufa deposits), and residual desert landforms. The geosites are attributed to the sedimentary, palaeogeographical, stratigraphical, palaeontological, and geomorphological geoheritage types. Scoring them by several criteria implies that two geosites (Naqb El-Rufuf and Naqb Bulaq) are national and four geosites (Naqb Assiut, Wadi El-Midawara, Gebel Taref, and Kharga Stadium) are regional in rank. The accessibility of some geosites is limited, and the Kharga Stadium geosite demonstrates significant vulnerability due to its location in the urban area. Generally, the analyses imply the presence of a valuable geoheritage resource in the Kharga Oasis. The outcomes of the present study also indicate the perspectives of scientific, educational, and touristic exploitation of the established geoheritage resources and the need in the development of the optimal policy for their effective management. Geopark creation seems to be a plausible instrument for the implementation of this policy, and its proposal requires further investigations of geological and cultural heritage of the Kharga Oasis.

Geochemical characteristics and thermal maturity modelling of Alam El Bueib/Kharita in the Tut Oil Field, Shushan Basin, North Western Desert, Egypt

Geochemical characteristics and thermal maturity modelling of Alam El Bueib/Kharita in the Tut Oil Field, Shushan Basin, North Western Desert, Egypt

3D geological and petrophysical modeling of Alam El-Bueib Formation using well logs and seismic data in Matruh Field, northwestern Egypt

There are several productive petroleum fields in the North Western Desert (WD) of Egypt, which received extensive investigations regarding their petroleum potential. However, a few studies tackled the Matruh Oil Field, which contains the oil prolific Early Cretaceous Alam El-Bueib Formation (AEB Fm) reservoir. The reservoir intervals of the AEB Fm show substantial lithological variations across the basin. Therefore, it is necessary to analyze the vertical and lateral distributions in terms of their lithological and petrophysical properties. To achieve this objective, wireline logs of four wells and 20-2D seismic lines were used to construct a depth-structure contour map for the studied part of the field. This map was used to build the field’s structure model and to identify the fault patterns in the basin through several seismic lines. Analyses of well logs data and lithology were used to estimate the petrophysical properties of AEB sandstone units AEB-1, AEB-3A, AEB-3C, and AEB-6. Results show that the AEB-6 Unit is the most promising hydrocarbon-bearing unit. It has a net pay of 20–160 feet, a shale volume of 5–20%, an effective porosity of 14–20%, and a hydrocarbon saturation of 70–88%. The structure-depth maps indicate a number of normal faults with two principal NE-SW and NW–SE trends, which probably act as structural traps in the Matruh Oil Field. The constructed structure-depth maps and calculated petrophysical parameters were used to build a three-dimensional reservoir model. A blind well was used to validate the accuracy and reliability of the facies, porosity, and saturation models for the AEB Fm units, ensuring a good match between log-derived data and built models. The AEB Fm shows regional heterogeneous variations in its petrophysical characteristics. It exhibits unconventional reservoir characteristics in a N–S direction and conventional reservoir characteristics in an E–W direction. This observed heterogeneity shows the need to carry out further investigations to comprehensively assess the hydrocarbon potential of AEB Fm in different areas of the Matruh Basin.

Metabolic profiling, antimicrobial, anticancer, and in vitro and in silico immunomodulatory investigation of Aspergillus niger OR730979 isolated from the Western Desert, Egypt.

Ten fungal species were isolated from soil in the Western Desert and Wadi El-Natron in Egypt. All fungal isolates were morphologically recognized down to the species level. Methanol extracts of fungal mycelia and ethyl acetate extracts of culture filtrate from the isolated fungi were evaluated for antimicrobial activity against six pathogenic bacteria and one pathogenic yeast (Candida albicans ATCC20231). Only ethyl acetate extracts of Fusarium circinatum, Aspergillus niger, and Aspergillus terreus culture filtrates showed significant antimicrobial activity against the majority of the investigated pathogens. The culture filtrate extract of Aspergillus niger exhibited notable cytotoxicity towards the breast cancer (MCF-7) cell line, with the lowest detected IC50 recorded at 8 μg/μl. Whereas Fusarium circinatum and Aspergillus terreus had IC50s of 15.91 μg/μl and 18 μg/μl, respectively. A gas chromatography-mass spectroscopy (GC-MS) investigation of A. niger's potent extract revealed 23 compounds with different biological activities. Glycidyleoleate was found to be the main extract component. Aspergillus niger extract was chosen to study its possible cytotoxic mechanism. The extract was found to induce apoptosis and cell cycle arrest at the < 2n stage. Despite a significant increase in caspases 8 and 9, the production levels of tumor necrosis factor α (TNF-α) and interleukin 6 (IL-6) have shown a significant decrease. The high interaction of glycidyleoleate against the studied cytokines' binding receptors was demonstrated via docking studies. In conclusion, the available data revealed that the culture filtrate extract of A. niger possesses promising antimicrobial, cytotoxic, and immunomodulatory properties.

Preliminary assessment of the Cambro-Ordovician reservoir potential from the Shushan basin, north Western Desert, Egypt

This study presents the first-ever preliminary assessment of the potential reservoir intervals from the Cambro-Ordovician Shifah Formation of the Shushan Basin, Western Desert. Seismic data, thin sections, XRD, XRF, and wireline logs were integrated to characterize the potential intervals. The study area is characterized by E-W and ENE-WSW trending steeply dipping normal faults creating a series of horsts, grabens, and half-graben structures. Based on the wireline logs-based petrophysical assessment, three potential reservoir intervals are identified with the Shifah Formation below 15000 ft depth. All the promising intervals show little shale volume (10–20 %) and 70–80 % hydrocarbon saturation, but the porosity is dominantly below 10%. The two potential sandstone intervals are composed of quartz arenites affected by silica cementation and mechanical compaction. These glauconite-bearing sandstones exhibit low-angle cross-lamination and planar lamination, likely deposited in a fluvial to shallow marine depositional environment. Both the tight sandstone intervals exhibit E-W, and NW-SE striking, closed, and partially open fractures which can contribute to the reservoir flow capacity. The third potential reservoir interval is an igneous intrusive body, composed of alkali syenite and exhibits secondary intraparticle porosity due to partial feldspar dissolution and minor fractures. The preliminary assessment presented in this work shed critical insights into the reservoir potential of the Shifah Formation.

Oil-source correlation and Paleozoic source rock analysis in the Siwa Basin, Western Desert: Insights from well-logs, Rock-Eval pyrolysis, and biomarker data

Understanding the origins of potential source rocks and unraveling the intricate connections between reservoir oils and their source formations in the Siwa Basin (Western Desert, Egypt) necessitate a thorough oil-source correlation investigation. This objective is achieved through a meticulous analysis of well-log responses, Rock-Eval pyrolysis, and biomarker data. The analysis of Total Organic Carbon across 31 samples representing Paleozoic formations in the Siwa A-1X well reveals a spectrum of organic richness ranging from 0.17 wt% to 2.04 wt%, thereby highlighting diverse levels of organic content and the presence of both Type II and Type III kerogen. Examination of the fingerprint characteristics of eight samples from the well suggests that the Dhiffah Formation comprises a blend of terrestrial and marine organic matter. Notably, a significant contribution from more oxidized residual organic matter and gas-prone Type III kerogen is observed. Contrarily, the Desouky and Zeitoun formations exhibit mixed organic matter indicative of a transitional environment, and thus featuring a pronounced marine influence within a more reducing setting, which is associated with Type II kerogen. Through analysis of five oil samples from different wells—SIWA L-1X, SIWA R-3X, SIWA D-1X, PTAH 5X, and PTAH 6X, it is evident that terrestrial organic matter, augmented by considerable marine input, was deposited in an oxidizing environment, and contains Type III kerogen. Geochemical scrutiny confirms the coexistence of mixed terrestrial organic matter within varying redox environments. Noteworthy is the uniformity of identified kerogen Types II and III across all samples, known to have potential for hydrocarbon generation. The discovery presented in this paper unveils captivating prospects concerning the genesis of oil in the Jurassic Safa reservoir, suggesting potential links to Paleozoic sources or even originating from the Safa Member itself. These revelations mark a substantial advancement in understanding source rock dynamics and their intricate relationship with reservoir oils within the Siwa Basin. By illuminating the processes of hydrocarbon genesis in the region, this study significantly enriches our knowledge base.

Late Albian-Cenomanian paleoenvironmental and paleoclimatic reconstructions in northeastern Gondwana: Palynological perceptions

The late Albian-Cenomanian (100.5–93.9 Ma) is considered a greenhouse world without permanent ice caps and with high eustatic sea levels. The high sea-level led to the flooding of low-lying coastal plains and the formation of extensive shallow shelf seas. Depositional conditions and ecosystems at these marginal and shallow shelf settings were affected by changes in environmental conditions, such as climate and vegetational ecosystems in surrounding regions. This study conducts palynomorph and palynofacies and lithofacies analysis of fifty-nine cutting samples from the North Qarun-1x well in the Gindi Basin (North Western Desert, Egypt) to assess the evolution of depositional and paleoenvironmental conditions as well as paleo-vegetation pattern in response to changes in climate and sea level. The sediment succession comprises the upper Albian to Cenomanian upper Kharita and Bahariya formations and Abu Roash G Member. Biostratigraphic analysis of palynomorph composition led to define seven interval zones of upper Albian-Cenomanian. At this time, Egypt was inundated by the southern margin of the Tethys Ocean, which led to the deposition of thick siliciclastic and carbonate facies in a marginal marine depositional environment. Statistical cluster analysis of particulate organic matter (POM) allowed three palynofacies assemblages (PFA-1 to PFA-3) to be recognized, indicating oscillating depositional conditions that shifted between fluvio-deltaic to marginal shallow marine, proximal, and distal inner neritic shelf environments. PFA-1 comprises the highest proportions of total phytoclasts, indicating fluvio-deltaic to marginal shallow marine conditions. PFA-2 is dominated by moderate abundances of AOM and phytoclasts, characterizing a proximal inner neritic shelf environment. PFA-3 consists of a slightly higher concentration of AOM compared to phytoclasts, indicating a distal inner neritic shelf environment with diminished terrestrial input and increased abundances of marine microplankton. Organic palynomorphs are abundant in mid-Cretaceous strata of northern Egypt. Abundant records of humidity indicators, mainly fern spores, along with other gymnosperms (mainly Taxodiaceae and Araucariaceae) compared to low aridity indicators of gnetalean Elaterates and Ephedroids along with non-gnetalean Classopollis suggest predominantly warm and humid conditions. Two intervals in the lower part of the Bahariya Formation and in the middle part of the Abu Roash G Member showed moderate to high abundances of aridity indicators and thus, warm arid to semi-arid climate events during the early and late Cenomanian.

IMPROVING THE PROPERTIES OF THE ACID RESISTANT MORTAR

 This research deals with the study of the production of an acid resistant mortar using local raw materials. The produced acid resistant mortar is to be used as a protective coat to protect the surface made of the ordinary concrete and the other surfaces which are in contact with corrosive aoids such as (H2SOa and HNO3) from the effect of the acids mentioned above.  Silicrete from the western desert was used as chemically inert solid filler. Different types of setting agents were added to the filler above one at a time to form a mix to which either the sodiurn silicate or the pota*.sium silicate solution was added as a binder. Sarnples of the raw materials were subjected to the mineralogical, chemical and physical tests to determine their reliability and to asses the optimum mix ratio. Ihe produced acid resistant silicate mortar coincides with the Arnerican Standards ASTM C466 is (1:2) (filler: binder) using 3%by weight either the Sodium florosilicate or the Ethyl acetate as a setting agent. 

Field Evaluation of Land Deterioration in Al - Mohammadi Basin Valley at Western Desert

The recurrent study was in including lots scientific details on land deterioration for Almehmedi valley basin. This basin is represented as distinguish sites because it possesses different morphology, geological properties, climate pattern, various land resources such as soils, vegetation and water resources. Conceptualization of this study was entirely prepared then results were different to discover the range of land degradation using field evolution on this basin, which its area was 1971.49 km2. Therefore basin lands were divided into six land unites via geomorphological terms. These terms were done using optical explanation on Land sat 8 satellite image. These unites are high plateaus, flat plateaus,  unbath, valleys, alluvial fans, flood plain. Moreover field investigation was applied using GLASOD physical, biological, chemical and saline deterioration. Thus, their cause was explained and measured the deterioration amounts within land units using tables  maps. The research study could clouded basin field spatial differences resulted in differing the valley basin from other  lands. Furthermore, it resulted in spatial relations amongst human iturimm and natural in this area.

Weathering Intensity, Paleoclimatic, and Progressive Expansion of Bottom-Water Anoxia in the Middle Jurassic Khatatba Formation, Southern Tethys: Geochemical Perspectives

The Jurassic Period was a significant phase of variable organic matter accumulation in paleo-shelf areas of the southern Tethys (Egypt). Reconstructing the paleoredox conditions, paleoclimate, and weathering intensity, along with the role of terrigenous sediment flux and mineralogical maturity, is important for understanding basin infill history and prevalent paleoenvironmental conditions. Here, inorganic geochemical data are presented from the Middle Jurassic Khatatba Formation and two samples from the underlying Ras Qattara and the overlying Masajid formations in the Jana-1x well, Shushan Basin, Western Desert. Twenty-four (24) whole-rock samples were analyzed for their major and trace element composition and carbonate content. The Khatatba Formation represents one of the major hydrocarbon source rocks in the North Western Desert, Egypt. Redox conditions were assessed based on enrichment factors of redox-sensitive elements Mo, V, U, and Co. Results revealed that the Khatatba Formation was deposited under predominant anoxic bottom and pore water conditions, in contrast to the oxic settings that were prevalent during the deposition of the Ras Qattara and Masajid formations. Continental weathering intensity and paleoclimate were reconstructed based on several proxies, such as the chemical index of alteration (CIA), K2O/Rb, Rb/Sr, Ln(Al2O3/Na2O), and Al/K ratios, indicating that the studied succession was deposited during alternating phases between weak and moderate weathering intensity under arid and warm-humid climates, respectively. Periods of enhanced continental weathering were associated with high values of clastic ratios such as Si/Al, Ti/Al, and Zr/Al, suggesting increased terrigenous sediment supply during intensified hydrological cycling. These ratios further provided inferences about the changes in sediment grain size, such as a change from shale to coarse silt- and sand-size fractions.

Petrographical and petrophysical rock typing for flow unit identification and permeability prediction in lower cretaceous reservoir AEB_IIIG, Western Desert, Egypt

The primary objective of this study is to identify and analyze the petrophysical properties of the newly investigated AEB_IIIG member reservoir in Meleiha West Deep (MWD) Field and to classify it into different rock types. Additionally, this research intends to develop mathematical equations that may be utilized to estimate permeability in uncored sections of the same well or in other wells where core samples are unavailable. The analysis focused on the pore hole records of ten wells that were drilled in MWD Field. The reservoir levels were identified, and their petrophysical parameters were evaluated using well logs and core data. We were able to recognize seven different types of rocks (petrophysical static rock type 1 (PSRT1) to PSRT7) using petrography data, the reservoir quality index (RQI), the flow zone index (FZI), R35, hydraulic flow units (HFUs), and stratigraphy modified Lorenz (SML) plots. The analysis of the petrophysical data shows that AEB_IIIG has unsteady net pay thicknesses over the area. It has a range of 8–25% shale volume, 12–17% effective porosity, and 72–92% hydrocarbon saturation. The RQI results show that psrt1, psrt2 and psrt3 have a good reservoir quality as indicated by high R35 and helium porosity, respectively. They contribute with more than 75% of the reservoir production. The equation derived for each rock type of AEB_IIIG reservoir can be employed to forecast the permeability value distribution inside the reservoir.

Diagenetic impact on unconventional tight carbonate reservoir of AR-F Member from the Abu Gharadig Field, north Western Desert, Egypt: insights from integrated combined sedimentological, petrographic, and petrophysical dataset

Diagenetic impact on unconventional tight carbonate reservoir of AR-F Member from the Abu Gharadig Field, north Western Desert, Egypt: insights from integrated combined sedimentological, petrographic, and petrophysical dataset

Sand Fairways Delineation by Post-Stack Seismic Inversion and Seismic Wave form Classification Integration, Sitra Area, North Western Desert, Egypt

Sand Fairways Delineation by Post-Stack Seismic Inversion and Seismic Wave form Classification Integration, Sitra Area, North Western Desert, Egypt

Integrated analysis of source rock evaluation and basin modelling in the Abu Gharadig Basin, Western Desert, Egypt: Insights from pyrolysis data, burial history, and trap characteristics

Source rock evaluation and basin modelling play crucial roles in understanding hydrocarbon potential. In this study, pyrolysis data from 92 shale ditch samples were employed to assess the source rocks in the Abu Gharadig Basin (Western Desert, Egypt). The organic richness ranged from 0.53% to 4.1% by weight, indicating varying hydrocarbon‐generating capabilities. Specifically, kerogen types II and III exhibited the potential to generate hydrocarbons, ranging from fair to good oil sources. The burial history analysis provided insights into the sedimentation and subsidence rates during different geological periods. The Late Jurassic‐Early Cretaceous period witnessed modest rates of sedimentation and subsidence. In contrast, the Oligocene and Late Miocene periods experienced medium burial rates, while the Late Cretaceous‐Early Tertiary period exhibited high burial rates. Specific formations were examined in detail, with the Apollonia Formation standing out as a significant hydrocarbon reservoir. It entered the early oil window at approximately 17.87 Ma and the wet gas window at about 17.41 Ma in the ASSIL‐1X well. However, it didn't reach the GPAA‐4 well. The Abu Roash ‘D’ member also showed promise, entering the early oil window at 38.20 and 47.38 Ma, and the wet gas window at 37.40 and 43.64 Ma. Similarly, the Abu Roash ‘F’ member exhibited favourable hydrocarbon generation, entering the early oil window at 39.90 and 54.86 Ma, and the wet gas window at 39.70 and 51.62 Ma in both the ASSIL‐1X and GPAA‐4 wells. Based on the analysis, the Apollonia, Abu Roash ‘D’ and ‘F’ members were identified as source rocks, while the Kharita, ‘C’, ‘E’ and ‘G’ members were recognized as reservoir rocks. The Abu Roash Shale acted as an effective seal rock. The geological structure of the region revealed the presence of NW‐SE normal faults, forming a three‐way dip closure trap. This research substantially enhances our comprehension of the hydrocarbon system within this basin. It achieves this by thoroughly investigating source rock evaluation, basin modelling and delivering invaluable insights into the mechanisms that govern hydrocarbon generation, expulsion and trap age.

Geologic causatives of the stratigraphic and structural heterogeneties of Baharyia formation, based on their seismic interpretation, Razzak field, Western Desert, Egypt

Evaluation of seismic attributes and seismic reflection characteristics analysis of Razzak Field was undertaken by subdividing the study area rock units. There are four seismo-facies units of varying parameters from top to bottom. These units are comparable to the Apollonia and Khoman Formations; the Abu-Roash Formation; Baharyia Formation and Alamein Formation. The seismo-facies unit 1 of the Apollonia and Khoman Formations reveal parallel to sub-parallel layering, with thickness increases northwards. The lithological distribution consists of limestone with minor clay intercalations with facies varying from middle neritic graded to outer neritic. Unit 2 of the Abu-Roash Formation shows divergent layering, with a thickness increasing gradually northwards and eastwards. The lithological distribution shows predominance of carbonate, sandstone occurring in minor portions and laterally graded into shale with littoral facies ranging to inner and middle neritic facies. Unit 3 of the Baharyia Formation reveals chaotic and oblique layering with a time thickness increases towards northeast and southwest parts, the lithological distribution exhibited sand and shale with minor limestone streaks, with facies varied changed from continental to inner-middle neritic, unit 4 of the Alamein Formation shows variation from parallel-subparallel orientation to oblique and chaotic with thickness increasing towards northwards and eastwards, the lithological distribution exhibited dolomitic limestone with minor streaks of limestone with facies varied from middle neritic facies to outer neritic and bathyal. Finally, the results are integrated to build up a seismo-stratigraphic model of the evaluated area of the northwestern Desert of Egypt. Seismic interpretation involves the construction of structure contour maps, in terms of time and depth, on the tops of the Apollonia, Abu-Roash, Baharyia and Alamein Formations. These maps show three structural closures, due to folding, that are dissected by NW–SE faults, analysis of relevant structural and stratigraphic seismic attributes such as root-mean-square amplitude, local structural dip, variance, ISO frequency component, sweetness and acoustic impedance average energy applied on reservoir tops, to enhance the visibility of faults, geological interpretation and the physical parameters of the subsurface related to lithology and stratigraphy for reservoir characterization. Finally, the results obtained are used to construct a seismic structural model. Integration of seismic and stratigraphic data is used to build a geological model of the northwestern Desert of Egypt.

Disentangling late quaternary fluvial and climatic drivers of palaeohydrological change in the Najaf Sea basin, Western Iraq

AbstractThe water resource provided by lake basins in the western desert of Iraq is important for human occupation of areas outside the Tigris‐Euphrates floodplain, both in the past and into the future. This paper presents the first geomorphological and geochronological study of the date of formation of the Najaf Sea and the only such study of any lake basin to the west of Mesopotamia. Geomorphological shoreline features and a palaeochannel linking to the Euphrates were studied and dated using optically stimulated luminescence (OSL) and radiocarbon dating. Provenance was determined using heavy mineral analysis. Past environments in the Najaf Sea were reconstructed by molluscan analysis. The earliest OSL ages date from c. 30 000 and 22 000 years ago and seem to predate lake formation. Younger OSL ages date the highest lake level at c. 19 m asl to between 1620–1760 AD (base) to 1906–1974 AD (near surface). The radiocarbon ages are affected by a freshwater reservoir effect, but the maximum ages recorded for either of the c. 15 m and c. 17 m asl shorelines are c. 800 cal. BC. This predates the first archaeological sites in the Najaf basin and is similar to maximum ages of c. 850 and c. 1100 cal. BC from the associated palaeochannel. This timing does not seem to be linked to a humid climate event. We therefore conclude that the establishment of the Najaf Sea in the Najaf basin occurred as a result of an avulsion event within the Euphrates system that diverted flow to the basin. The trigger for this avulsion event likely related to rapid sediment accumulation and may have been either autogenic or driven by human activity. This study therefore suggests that Najaf Sea formation facilitated human expansion beyond the Tigris‐ Euphrates floodplain and occurred due to avulsion of the Euphrates.

A Comparative Analysis and Environmental Interpretation of the First Cycle of Nfayil Formation in Two Distinct Southern Desert Locations, Iraq

Nfayil Formation (Middle Miocene) is considered the equivalent of Fatha Formation; it is exposed in the western and southern Desert of Iraq with two members: a carbonate Lower Member that is composed of three cycles of limestone and marlstone intercalation and an Upper clastic Member of sandstone and claystone with thin layers of limestone. It extends from the western to the southern desert with a systematic succession of two or three cycles of lower members each one consisting of an interbedding of soft olive-green marl with medium tough shelly limestone rich with oyster shells. The upper member disappears in many localities due to erosion activity. From the field observation this succession was normally exposed in the southern Desert at the western parts of Al-Muthanna Governorate to the south of Dewaniyah Governorate, while in the eastern part of Al-Muthanna Governorate to the south of Al-Nasiriya Governorate, the beds showed a different lithology and fossil content. The olive-green marl turned to be rusty red with a higher content of fossils, the shelly limestone bed rich with oyster shells became red in colour, rusty and the oyster shells were substituted by pelecypods shells with the same concentration. A microfacies analysis study supported by chemical and X-ray analysis was carried out to predict the depositional environment and deposition circumstances in both sections. The thin section, chemical analysis and X-ray analysis were accomplished at the laboratories of the Iraq Geological Survey. Chemical analyses showed a high ratio of MgO oxide in Nasiriya section compare with Samawa section, that result was supported by X-ray analyses which refer to calcite mineral as the only mineral exists in Samawa beds wile in Nasiriya minerals of dolomite, quartz, feldspar and clay minerals were appeared.Environments extracted from thin section study showed more local fluctuations in sea level in Samawa section.