Subsurface Sections Research Articles

Paleoclimate evidence using Nannopaleontology from Mushorah Formation in Northwestern Iraq

Calcareous nannofossils are classified from the Mushorah Formation from two subsurface sections in Butmah 15-well, Butmah oil field, and Sfaia 41-well, Sfaia oil field, Northwestern Iraq. This Nannopaleontological classification of these calcareous nannofossils led to the determination of many species. Calcareous nannofossils are dominated by the following taxon: Chiastozygaceae family with two of the Chiastozygus genus, three species of the Reinhardtites genus and three species of the Zeugrhabdotus genus, Axopodorhabdaceae family with one species of the Cribrocorona genus, Eiffellithaceae family with two of the Eiffellithus genus, Prediscosphaeraceae family with two of the Prediscosphaera genus, Cretarhabdaceae family with two of the Retecapsa genus, Rhagodiscaceae family with two of the Rhagodiscus genus, Watznaueriaceae family with two of the Cyclagelosphaera genus, with five of the Watznaueria genus, Arkhangelskiales family with two of the, Arkhangelskiella genus, with two of the Broinsonia genus, one of the Misceomarginatus genus, Calyptrosphaeraceae family with three of the Calculites genus with one of the Lucianorhabdus genus, Microrhabdulaceae family with three of the Lithraphidites genus, Polycyclolithaceae family with four of the Eprolithus genus, with three of the Lithastrinus genus, with five of the Micula genus, two of the Quadrum genus, one of the Rucinolithus genus, three of the Ceratolithoides genus. Our investigation focuses on the response of the assemblage of the Watznaueria spp., it can be concluded from higher speciation for calcareous nannofossils that the bloom at Campanian has an increase in temperature has implications for climate change impacts on the ecosystem.

Source Rock Evaluation and Hydrocarbon Generation Potential of the Cretaceous (Dokan and Gulneri) Formations in Bai Hassan-13 Well Section, Kurdistan, North of Iraq

Eleven cutting rock samples from both Dokan and Gulneri formations (Cretaceous) in one subsurface section of Bai Hassan-13 (BH-13) well in northern Iraq were studied by using two techniques for hydrocarbon generation potentiality. The geochemical technique included Rock-Eval Pyrolysis analysis, The optical technique was achieved by studying palynological slides. The rock-Eval pyrolysis results showed that Dokan Formation has total organic carbon (TOC) wt.% ranging between 1.16 % and 2.3 % (good to very good), Gulneri Formation has a high TOC of 1.34 % and 4.64 % (good to excellent) quantity of organic matter. About the quality of organic matter, both Dokan and Gulneri formations are composed of kerogen types I and II. The organic matter of the Dokan Formation is not indigenous (migrated), one sample of the Gulneri Formation is indigenous the other one is located on the slanted line separating the Indigenous from non-indigenous organic matter. The organic matter within the two formations are thermally immature source rock, Therefore, they cannot generate oil and gas. The palynological study revealed that amorphous organic matter is the predominant organic matter component in both formations with more than 89%, whereas phytoclasts and palynomorphs comprised only a few percentages. There is no great variation in the percentages of the mentioned organic matter components, except a slight increase in the percentage of phytoclasts and palynomorphs in the lower part of the Dokan Formation, therefore one primary palynofacies type can be recognized, and divided into two secondary palynofacies. Through plotting Tyson's Amorphous, phytoclasts, and palynomorphs (APP) diagram, it is clear that the two formations are deposited in a distal suboxic to anoxic basin.

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.

Depositional environments and thermal maturity of the hydrocarbon source rocks in the Devonian–Early carboniferous Ora Formation from palynological organic petrographic investigations in northern and western Iraq

The study investigates the palynofacies, organic matter character, and hydrocarbon generation potential of this rock unit, based on surface and subsurface samples from the Ora Formation type-section in extreme northern Iraq and the Akkas-3 well in western Iraq, respectively. Dark, mostly oxidized, gelified platy amorphous organic matter (AOM) dominates the palynological components in the surface section, in addition to a few rounded spores and structured phytoclasts. In contrast, palynomorphs, including Ambitisporites avitus, Aneurospora spp., Vallatisporites verrucosus, Acinosporites spp., Verrucosisporites nitidus and the algae Botryococcus, are predominant in studied samples from the Akkas-3 well. Statistical cluster analysis identified three palynofacies types in the surface section based on stratigraphic variations in the particulate organic matter. These vary from high amorphous organic matter (AOM), moderate phytoclast, and low palynomorph abundances that represent proximal suboxic–anoxic shelfal environments to moderate to good AOM and low to moderate palynomorph abundances that represent distal suboxic–anoxic or distal dysoxic–anoxic shelfal environments. The organic petrographic study of the outcrop section also revealed the strong effect of oxidation, where dispersed terrigenous and amorphous organic materials in the form of granular and gelified forms dominate and reflect a terrestrial origin of these components. In the subsurface section, a mixed terrestrial and less marine or lacustrine origin characterized the studied organic matter, where land plant spores (sporinite), in addition to vitrinite and inertinite, are dominant with a few scattered liptinite macerals. The difference in thermal maturity between the outcrop and subsurface samples is likely due to the higher tectonic burial of the outcrop samples that form part of the Northern Thrust Zone of Iraq. Nevertheless, higher abundances of AOM (oil-prone kerogen type II) accumulated in the northern outcrop type section. This might imply that the Ora Formation has a higher potential for hydrocarbon production north of the Akkas field.

Facies controls and tectonic evolution on oil accumulation and entrapment in the Cenomanian Abu Roash G member, northern-central Egypt: Deltaic and channel sandstones as good reservoirs

Along northern-central Egypt, the oil accumulation and entrapment were mainly controlled by variable parameters including the stratigraphic architecture, sedimentary features, and tectonic evolutions. The present paper presents a new model for oil occurrences in the Abu Roash G Member (Cenomanian) along Gindi, Abu Gharadig and to a few extents the Beni Suef basins, in the northern-central part of the Western and Eastern Deserts of Egypt. The studied concessions include the Wadi El Rayan, East Bahariya and El Diyur (Gindi basin and Abu Gharadig basins, Western Desert) and the Ghariboun (Beni Suef Basin, Eastern Desert) fields. Twenty sedimentary facies were recorded from the studied subsurface sections of the Abu Roash G Member and grouped into three facies associations. A new depositional model is achieved where estuarine, open marine, deltaic distributaries, and tidal channel deposits are the main facies associations recorded in the studied Abu Roash “G". These deltaic and channel deposits occurred as an arch like form between open marine and estuarine deposits. These deltaic and tidal channel sandstone deposits act as a good reservoir to accumulate oil from nearby areas. As well, these areas were subjected to the well-known Syrian arch compressional deformation that affected northern Egypt during the Mesozoic, up to late Senonian time. A regional NE-SW oriented fold system took place, forming NE-SW oriented ridges in addition to the dextral strike-slip movement that took place along these ridges because of this compressional deformation.To sum up, oil accumulation in the studied Abu Roash G Member was mainly controlled by facies distribution mainly of channel sandstone enhanced by the tectonic movements (Syrian Arc System) affecting the areas studied.

Microfacies and Depositional Environments Analyses of the Hartha Formation at Balad Oil Field, Central Iraq

The Hartha Formation (Late Campanian-Maastrichtian) has been recognized as a potential reservoir for hydrocarbons in various oilfields within the Mesopotamian basin in central Iraq. The formation has conformable upper contact with the overlying Shiranish Formation but unconformable lower contact with the underlying Mushorah Formation. This formation has been stratigraphically divided into two main parts. The lower part is particularly significant as it is recognized as an important stratigraphic unit due to the presence of oil shows. Five subsurface sections and many thin sections of the Hartha Formation (Late Campanian-Maastrichtian) were studied to unravel the depositional facies and environments. The sedimentary microfacies of the Hartha Formation in the Balad oil field include mudstone, wackestone, wackestone to packstone, packstone, Packstone to Grainstone, and Rudstone. These depositional microfacies have been subdivided according to their primary and diagenetic constituents into six sub-microfacies. The microfacies have been deposited in deep shelf margin, open shelf, and foreslope of varying salinities and energy levels. Cementation, dolomitization, compaction and pressure solution (stylolitization ), and dissolution are observed affecting variably both ground mass and particles. These diagenetic processes have both positive and negative effects on porosity types, causing fluctuations in porosity levels. The primary pore types identified within the study wells include interparticle porosity, intercrystal porosity, moldic porosity, vuggy porosity, channel porosity, and fracture porosity.

Depositional architecture of the tide-dominated late Oligocene hydrocarbon reservoirs in the Tapti-Daman block, Mumbai Offshore basin, India

The intricate interaction between tidal and river currents across a gently sloping shelf area complicates the geological interpretation of sedimentary deposits in subsurface sections. This study comprehensively analyzes the depositional framework and facies architecture in the late Oligocene siliciclastic succession of the Daman Formation, Mumbai Offshore Basin, which shows subtle changes in depositional stacking pattern in response to shoreline shifts. The late Oligocene siliciclastic succession being a major hydrocarbon producer in the Mumbai Offshore Basin; this research also aims to enhance the optimization of reserve exploitation and prospectivity evaluation. A detailed analysis was conducted using well-logs and seismic data integrated with available geological data. The Oligo-Miocene sequence demonstrates a coarsening-upward facies trend until the late Oligocene, followed by a fining-upward facies trend during the early Miocene and characterized by numerous stacked sandstone layers. The facies distribution pattern, sedimentary characteristics, and progradational geometry suggest a deltaic system dominated by tides for the late Oligocene succession and the latter part of the early Oligocene succession. The early Miocene succession shows a reversal in depositional trend with a retrogradation pattern. The late Oligocene deltaic deposits show a very high sediment load deposited during the peak river discharge from the Narmada-Tapti River system. The gentle depositional slope allowed redistribution of sediments by tidal currents. The deltaic system was further resolved into subaqueous mouth bar, delta front, and prodelta facies associations based on facies modeling. The correlation of the facies model with the regional depositional setup indicates that the late Oligocene succession corresponds to a third-order highstand system tract (HST) cycle.

Large Benthic Foraminifera Biozonation of Mauddud Formation in Selected Section from Balad Oil Field, Central Iraq

Three subsurface sections Ba-1, Ba-4, and Ba-8, and sixty-five thin sections were examined to investigate the biostratigraphy of the Mauddud Formation (age Early Albian - Late Cenomanian) within the Balad Oil Field located in central Iraq. The formation is lithologically composed of dolomitic limestone, creamy oolitic limestone, and shale. Orbitolina qatarica, Orbitolina sefini, and Orbitolina concava range zones were distinguished as biozones, including the Late Albian (Orbitolina qatarica), Late Albian to Early Cenomanian (Orbitolina sefini), and Early-Cenomanian (Orbitolina concava) zones. The age of these biozones confirmed the extent throughout the early Cenomanian age. Fossils of twenty-seven species of Foraminifera, including Conicorbitolina conica, Miliolids, Neoiraqia convexa, Nezzazata, orbitolina sp., Spiroluculina sp., and Trocholina sp., and others like Coral, gastropods, and rudest were identified.

Organic geochemistry of the middle Paleozoic Ora Formation in Iraq: Implications for source rock assessment and hydrocarbon potentiality

The Ora Formation (late Devonian–early Carboniferous) is thought to be a potential source rocks for the Paleozoic petroleum system of Iraq. The source potential from the Ora Formation is evaluated for the first time ever in this study from western and northern Iraq which integrates data from organic geochemistry including Total Organic Carbon (TOC) analysis, HAWK pyrolysis, gas chromatography (GC), and gas chromatography mass spectrometry (GC-MS) and mineralogical X-ray diffraction and scanning electron microscopy. The shale and muddy carbonate succession within the Ora Formation from surface section in northernmost Iraq and subsurface section from two wells (Akkas-1 and Akkas −3) from western Iraq have been employed to assess the source rock potentiality, thermal maturity, kerogen type, organic content, and depositional environment. In addition to organic geochemical analyses, mineralogical XRD and SEM-EDS were used to support the paleoenvironmental interpretation of the Ora Formation. The results from TOC and HAWK analyses reveal that the Ora Formation ranges from poor to good as a source rock. However, the HAWK data suggests that the surface samples from northernmost Iraq are highly mature, highly weathered, or both. Kerogen analysis revealed that the Ora Formation contains immature type III and mixed II-III kerogens. Low TOC values were attributed to factors such as significant clastic input, weathering effects, and the prevailing oxic environment during deposition. The presence of detrital influx of quartz and feldspars, along with the occurrence of illite and kaolinite clay minerals, suggest a detrital input with weathering influence under hot arid and warm humid conditions. Biomarker analysis of the light hydrocarbons using GC and GC-MS revealed that these light hydrocarbons were generated from marine planktonic algae sources, possibly with some contributions from terrestrial and/or microbially reworked organic matter. These high mature light hydrocarbons in subsurface section were originated from anoxic marine shale source rocks. They were most likely from the Cambro-Ordovician Khabour Formation and were contaminated from another source.

Paleoclimate changes across the Cenomanian–Santonian transition at the southern Neo-Tethys margin (SW Iran): An integrated approach

The Cenomanian–Santonian (C–S) carbonate successions include valuable petroleum reservoirs in the Zagros Basin. They also provide important information on the paleogeographic setting, paleoclimatic conditions, and tectonic evolution of the southern Neo-Tethys margin. This study focuses on the paleoclimatic changes across the C–S transition using the petrographical, petrophysical, paleontological, major and trace element and isotope geochemical data from three subsurface sections selected from the southern Dezful Embayment and northwestern part of the Persian Gulf. Remarkable differences in allochemical (skeletal and non-skeletal) elements indicate dissimilar paleoclimatic conditions during the Cenomanian–Turonian and Santonian. Paleoexposure events are related to diagenetic processes such as extensive meteoric dissolution (karstification) and the development of bauxitic–lateritic paleosols with high Fe, Al, and kaolinite concentrations indicating warm and humid (tropical) conditions. Increased values of Fe, Al, Rb, and 87Sr/86Sr isotopic ratios and depletion of Ca, Sr, δ18O, and δ13C considered together indicate meteoric diagenetic effects under this paleoclimatic condition. Spectral gamma measurements are used to investigate paleoclimatic conditions. Low content of Uranium (U) throughout the transgressive systems tract (TST) and high concentration in the regressive systems tract (RST) along with low contents of kaolinite within the Santonian sequence denote the predominance of arid conditions. The major fall in U concentrations at the Cenomanian–Turonian interface (CT-Exposure Surface) could be regarded as an outcome of the fall in the relative sea-level and a proxy of oxidizing conditions (Th/U > 7) that could be the consequence of a change in paleoclimate from humid/semi-humid to humid. Evidence for a 3–4 °C decrease in paleo-temperature and increase in aridity are recorded during the Cenomanian–Santonian transition in the Zagros Basin, which is in close agreement with global trends. This cooling pattern is attributed to a decline in atmospheric CO2 levels and alterations in oceanic circulation, specifically an increase in meridional circulation.

Reservoir characteristics of the middle Eocene Avanah Formation in Erbil governorate, northern Iraq: Integration of outcrop and subsurface data

The current work investigate the petrophysical characteristics of the Middle Eocene Avanah Formation in the Erbil Governorate using IP software to analyze the well data, integrated with the 
 petrographic investigation of the formation in the nearest outcrop in the Gomaspan section. Well logging data revealed that the main lithology of the formation is limestone and dolostone while the lithology in the Gomaspan section is composed of limestone, dolomitic limestone, marly dolomitic limestone, and thin beds of shale. The lower dolomitic unit in the subsurface section of the formation is believed to be the most suitable reservoir unit due to good petrophysical characteristics including, low water saturation, high porous medium, and the presence of movable hydrocarbon. To measure porosities, a variety of well logging techniques were used in this study. The investigated formation was divided into Avanah dense (limestone unit) and Avanah porous (dolostone unit) based on their porous components. The petrographic study shows that most pore types of the formation are secondary and represented mainly by vuggy, moldic, intercrystalline, and fracture types. Most of the fractures in the upper limestone units are filled by calcite cement. The study claimed that the lower part of the formation (dolostone unit) in both sections is considered a good reservoir.

Depositional Model of Early-Middle Turonian Deep Water Gulneri Formation, in Selected Outcrop and Subsurface Sections in Northern Iraq

The Gulneri Formation (Early-Middle Turonian) Deep-water depositional model was constructed using detailed microfacies analysis from the northern Iraqi wells of Kirkuk (K-116) and Bai Hassan (BH-81) as well as the Dokan outcropped area. In the outcropped section, the formation consists of 2 m of thin friable marly limestone with high organic matter and thin-bedded black shale in addition to boulder and gravel-like limestone masses in the lower part. In the K-116 and BH-81 wells, the formation is 4.3 m and 9 m thick, respectively. It is composed mainly of black bituminous, pyritic calcareous shale, and shaley limestone with scattered glauconites. Petrographic studies of seventeen thin sections of the Gulneri rocks reveal that the pelagic/deep marine faunas are the dominant skeletal grain in the micritic groundmass. Three main microfacies were recognized in the studied rocks of the Gulneri Formation, namely lime mudstone, lime wackestone, and lime packstone. However, the latter is absent in the Dokan section. According to their environmental interpretation, these microfacies were grouped into two facies associations (basinal deep water and deep shelf). Based on the results of petrographic and microfacies analyses, it is concluded that the Gulneri Formation was deposited in a basinal deep marine environment with quiet and reducing conditions in the Dokan section and a basinal deep marine environment in the K-116 and BH-81 wells which changed at intervals to a shallower deep shelf setting toward the upper part with semi reducing conditions. The euxinic deep basin that formed at the beginning of the Kurdistan foreland basin's formation was quite anoxic and deeper from the northeast to the relatively shallower basin with semi-reduced conditions towards the southwest. This is how the depositional model of the Gulneri Formation in northern Iraq changed.

Diagenesis processes of the Gulneri Shale, Kometan, Mushorah formations within the upper Turonian - lower Campanian Supersequence from Bai Hassan area, North of Iraq

The upper Turonian - lower Campanian Supersequence is characterized with fine-grained, mixed siliciclastic-carbonate middle shelf to sub-basinal depositional system. The present study included the study of vertical and lateral changes of the diagenesis processes of the Gulneri shale, Kometan and Mushorah Formations within the sequences of the (upper Turonian-lower Campanian) cycle in two subsurface sections within the Dome of Daoud in the Bai Hassan field - northern Iraq. The first is represented by a section (BH-16) with a thickness of (213) m. In contrast, the second is represented by a section (BH-86) and a thickness of (233) m. The lithostratigraphy of the rock units of this study are consisting (206) slides were studied, (80) for well (BH-16) and (126) for well (BH-86).The study showed that the sequences of this cycle are unconformity with the lower Dokan Formation and upper contact with Hartha. The petrographic study showed that the rocks of the study were exposed to many diagenesis processes, like cementation, dolomitization, neomorphism, dissolution and compaction according to the degree of their prevalence with a large spread of locally authigenic minerals represented by the widespread pyrite mineral during the two sections of the study, in addition to a few presence of glauconite mineral. Depending on the petrographic description of the diagenesis processes, the vertical and lateral changes of the diagenesis processes were studied, and the diagenesis environments of the formations under study were deduced, where it was found that all the rocks of the two sections of the study were formed in the early stages of the diagenesis processes within the vadose environments as a result of exposure to tectonic processes that helped uplift their rocks to the surface and be affected by meteoric water.

Biostratigraphy of Shiranish Formation from Selected Wells, Central of Iraq

The Quantitative high-resolution planktonic foraminiferal analysis of the subsurface section in three selected wells in the Ajeel Oil Field (Aj-8, Aj-12, and Aj-15) in Tikrit Governorate, Central Iraq has revealed that Shiranish Formation deposited in Late Campanian- Latest Maastrichtian age. This formation consists mainly of marly and marly limestone yielding diverse planktonic foraminiferal assemblages and calcareous benthic foraminifera, with a total of 46 species that belong to 23 genera, Three zones and four subzones, which cover the Late Campanian to the Latest Maastrichtian, were identified based on the recorded planktonic foraminifera and their ranges. They are as follows:1. Globotruncana aegyptiaca Zone that dated to be Late Campanian 2. Gansserina gansseri Zone that refers to Early Maastrichtian 3. Abathomphalus mayaroensis Zone that indicates Late Maastrichtian, in this section, the Abathomphalus mayaroensis Zone is divided into four subzones, namely in that order from bottom to top: Racemiguembelina fructicosa (Early Late Maastrichtian), Pseudoguembelina hariaensis (Middle-Late Maastrichtian), P. palpebra ( Late Late Maastrichtian), and Plummerita hantkeninoides (latest Maastrichtian).

Blended acquisition with temporally signatured/modulated and spatially dispersed source array: The first pilot survey onshore Abu Dhabi

AbstractRecently, we established a blended‐acquisition method: temporally signatured and/or modulated and spatially dispersed source array that jointly uses various signaturing and/or modulation in the time dimension and dispersed source array in the space dimension. We acquired and processed the first pilot programme with our method onshore Abu Dhabi. In this paper, we review the resulting acquisition‐productivity enhancement in the time dimension and discuss it in the space dimension as well. We then review the deblended‐data‐reconstruction processing, followed by imaging processing, and discuss their performance and resulting data quality. We last establish a relationship between the acquisition productivity and the processing performance. We found that this method significantly enhances the acquisition productivity compared to conventional blending methods. For the processing performance, the deblended data can successfully be reconstructed from the blended data; afterwards, the subsurface sections can naturally be imaged from the deblended data. Furthermore, this method owns a relationship: The deblended‐data‐reconstruction performance increases with the acquisition time (i.e. the acquisition effort that is inversely proportional to the acquisition productivity) up to a plateau; the imaging processing improves the data quality as the flow makes progress and eventually reaches a high data quality after poststack processing, regardless of the acquisition effort.

Palynological analysis (biochronostratigraphy and paleoenvironments) from a fossil-Lagerstätte section within the Late Paleozoic Ice Age unit of the Paraná Basin (Itararé Group), Western Gondwana

A diverse and exceptionally preserved fossil association occurs in Campáleo Outcrop black shales of the upper Itararé Group, correlated to the Lontras Member, considered representative of the Pennsylvanian–Permian transition in the Paraná Basin, Brazil. In this paper, we present the palynological records from 20 stratigraphic horizons of these shales and related strata, which revealed 21 taxa of spores, 33 of pollen grains, two species of fungi, one species of Chlorophyceae and two species of Prasinophyceae. The section is correlated to the Vittatina costabilis Zone, due to the records of certain guide species, such as Converrucosisporites confluens, Illinites unicus and several species of Vittatina. An additional subsurface section (TC-4 core) partially correlated with the Campáleo Outcrop and comprising the passage of the Crucisaccites monoletus and Vittatina costabilis palynozones was also studied in order to support the stratigraphic positioning. Once combined with the stratigraphic positioning in the basal portion to the Lontras Shale, it allows us to consider it around the Pennsylvanian–Permian boundary, probably in the Gzhelian to age of the Campáleo Outcrop. We observed distinct palynofloristic compositions from (i) the rhythmic shale with dropstones (basal portion) and from (ii) the fossiliferous black shales (upper portion). The former presents a large dominance (about 90 %) of pollen grains (xerophylous elements) and low frequency (about 7 %) of spores (meso-hygrophylous), while the results of the latter are conversely. Marine palynormorphs were recorded herein only from the rhythmic shale. The palynological assemblages on the base of the Campáleo Outcrop demonstrated a more intense sediment supply, bringing sporomorphs from more distant regions being represented mainly by xerophylic flora, indicating the existence of regions devoid of ice cover, where forests could develop, as occur in seasonal climate regions. The upper level of the Campáleo Outcrop characterizes one of the predominance of spores (hygrophylic communities) in these palynological associations supported by the large number of insects found that indicates proximity to the coastline, little transport (spore tetrads), poor contribution of more distant continental sediments (low expressiveness of pollen grains) and low salinity water, due to the absence of marine palynomorphs, representing a reducing restricted marine environment. This data integrated with the stratigraphic context and other geological data evidenced changes in sea level due to the climatic oscillations in the course of the LPIA that influenced the sediment supply and the distance of the coastline in this region of the Paraná Basin.

Environmental and vegetation dynamics through the Oligocene to Early Miocene of North Africa (Egypt)

This study documents palynomorph assemblages from the Oligocene through the Early Miocene, across the significant Warm-house to Cool-house transition, using a subsurface section from the AG-5 well, north Western Desert of Egypt. Although the Paleogene and Neogene strata occupied a large area of the land, little about vegetation and ecosystem processes that shaped the climate and biodiversity during this time window is known. Here, based on a comprehensive palynological analysis of the Oligocene to Early Miocene Dabaa and Moghra formations encountered in the AG-5 well, we show that the studied area was characterized by a humid tropical to subtropical climate during the Oligocene-Miocene time interval. The obtained results provide clear evidence of the poorly known Paleogene-Neogene ecosystem in North Africa. In terms of palynostratigraphical framework, three palynozones covering the late Oligocene-Early Miocene interval are recognized. Moreover, the recovered palynomorphs inferred a deposition of the Dabaa Formation under a normal marine, inner shelf to littoral environment. However, for the basal part of the Moghra Formation, a deposition in an offshore marine environment, outer shelf (high sea level, 100–200 m depth) is assumed, whereas a deposition in shallow coastal lagoons, estuary, or delta environment (low sea level) is presumed for its uppermost part.

Biostratigraphy of Hartha Formation from Selected Wells in Nasiriyah Oil Field, Southern Iraq

The Hartha Formation has been investigated from a biostratigraphic view in three subsurface sections in the Nasiriyah Oil field, wells Ns1, Ns3, and Ns4, South of Iraq. Hartha Formation is composed of limestone and has various areas of intense dolomitization alternating with marly limestone. The formation ranges in thickness from 126 to 182 meters. Thirteen large and small benthic foraminifer species and genera are identified from Hartha Formation. Based on the large benthic foraminifer's assemblage, one distinct biozone was recognized after an examination of the paleontological datum in the investigated area showed that the studied wells contained a diversity of foraminiferal species, the larger foraminifers biozone was proposed: Orbitoides medius- Orbitoides tissoti - Orbitoides gensacicus -Orbitoides apiculatus - Omphalocyclus macroporus assemblage zone (Late Campanian- Early Maastrichtian), this biozone divided in two range subzone: Orbitoides medius Partial Range Zone (Late Campanian) and Omphalocyclus macroporus Range Zone (Early Maastrichtian). This biozone indicated that the Hartha Formation deposited through (Late Campanian- Early Maastrichtian).

Hydrocarbon Potential and Depositional Environment of the Shiranish Formation in Northern Iraq

Shiranish Formation at three localities in Northern Iraq (Pulkana, Dokan, and Sufaya) was studied to determine hydrocarbon generation potential and conditions of the depositional environment. For this purpose, 15 rock samples were collected from subsurface sections (Pulkana and Sufaya oil fields) and 5 surface samples from the Shiranish outcrop in the Dokan area. These samples were subjected to Rock-Eval pyrolysis analysis, in addition to biomarker analysis of the bitumen extract of one sample. Total organic carbon, S2, and hydrogen index values of the Formation samples from the Sufaya oil field, and the Dokan outcrop were generally low; indicating that Shiranish Formation is non-hydrocarbon source rocks. On the other hand, the Total organic carbon, S2, and HI of the Shiranish Formation for Pulkana oilfield samples are generally high; indicating that Shiranish Formation can be regarded as a fair source of rocks. Tmax and biomarker data indicate that the organic matter of the Shiranish Formation is immature-early mature. Moreover, the hydrogen index, oxygen index, and biomarker data indicate that the Shiranish Formation contains type II and II/III and was deposited under an anoxic depositional environment at Pulkana. At Sufaya and Dokan, Shiranish Formation contains type III and IV kerogen deposited in a more oxic environment.

Neoichnology of vertebrate traces along the western barrier coast of Ukraine: preservation potential and subsurface visualization

A diverse quite of vertebrate traces covers beach, aeolian, and bay-side (deflation flats) surfaces along the NW Black Sea coast of Ukraine. These include avian, ungulate, and canid footprints, as well as mammal burrows (length >5 cm; depth ~2 cm). The preservation of biogenic structures is enhanced by rapid burial (low-energy sedimentation or event deposition), algal mat formation, and salt encrustation. Continuous high-frequency (800 MHz) ground-penetrating radar (GPR) imaging aided in visualizing subsurface sections of an active burrow complex within a beach-dune ridge. Images near an active fox burrow captured distinct subsurface anomalies (point-source hyperbolic diffractions) in the upper aeolian section above the water table. Unfilled tunnel sections are easily distinguished from buried roots and other targets based on signal velocity and polarity reversals relative to air-to-sediment response at the ground surface. The diffraction geometry (angle) is related to signal velocity, providing valuable information about relative saturation of the overlying substrate. Decimeter-scale deformation of shallow reflections may be attributed to tracking surfaces, with similar examples found immediately below modern surfaces affected by anthropogenic trampling. It is likely that muddy lagoonal tracking surfaces may be preserved under layers of sand (overwash or aeolian deposition) and, following saltwater expulsion, may be recognized in geophysical images as clear deformed paleo-surfaces. Heavy-mineral concentrations (e.g. magnetite-rich sand) are common for beach and dune horizons that have undergone reworking and such anomalies often accentuate physical and biogenic deformation structures. Due to moderate-to-high fraction of ferri- and paramagnetic minerals, these anomalies are also well-expressed in GPR images due to its electromagnetic signal response. A conceptual framework of trace preservation potential (taphonomy) and geophysical recognition (GPR) suitability is proposed for this coastal region, with implications to paleo-environmental reconstruction.