Open Basin Research Articles

A Stratigraphic Analysis Of The Khasib, Tanuma And Sa’di Formations In The Majnoon Oil Field, Southern Iraq

The carbonate platform is the environment of Khasib, Tanuma and Sa’di formations which were deposited within open shelf settings at the Majnoon oil field in eight microfacies. The deposition, based on the analysis of microfacies, took place within shallow open marine, shoal environment, deep marine and basin environments. Five third order cycles of succession consist in MJ-12 oil well and three third order cycles in the MJ-15 oil well. They represent successive episodes of sea level rise and standstills. The succession in the study area was formed in a high subsidence environment, reflecting the high subsidence as the main controlling factor in the sequence creation. Because of a significant transgression, the Khasib, Tanuma, and Sa’di formations were deposited on an extremely subsidential carbonate base, where sea level succession involved episodes of rise and standstills.

Geochemical evidences on the origin and paleo‐oceanic depositional setting of the Naga Hills Ophiolite cherts, North East India

The Jurassic‐Cretaceous chert of the Naga Hills Ophiolite (NHO) is tectonically juxtaposed with the mafics (mostly basalts) and ultramafics along the Indo‐Myanmar Ranges (IMR), which constitute the southeastern extension of the Indus‐Yarlung‐Tsangpo Suture. Petrographic and geochemical studies were taken up to determine their origin and paleo‐oceanic depositional environments. Cryptocrystalline quartz is intimately mixed with iron oxides and clay minerals containing poorly preserved radiolarians. Geochemical signatures indicate a predominantly biogenic origin for the NHO cherts, which were derived from radiolarians and other siliceous microfossils. Rare earth elements and trace element abundances indicate predominant contribution by scavenging from seawater with the minor influence of low‐temperature hydrothermal activity. Most of the NHO cherts were deposited in an open ocean basin where oxic conditions prevailed. Geochemical signatures endorsed by field relations of chert, pillow basalts, and limestone within the oceanic plate indicate that chert formation continued in the vicinity of oceanic islands. Organic matter played a pivotal role in regulating oxic‐anoxic conditions during deposition, as evidenced by redox‐sensitive trace elements. These cherts, envisaged to have been originally part of the Tethys, were tectonically emplaced during the Middle Eocene. They now constitute part of the NHO along the IMR.

Petrogenesis of a nepheline syenite from parts of the Chotanagpur Granite Gneissic Complex: implications for Neoproterozoic crustal extension in the East Indian Shield

AbstractThe North Purulia Shear Zone that dissects the granulite basement of the Chotanagpur Granite Gneissic Complex of the East Indian Shield exposes a deformed and metamorphosed nepheline syenite. The studied ‘foid-monzosyenite’ shows high abundances of large ion lithophile elements and high field strength elements with low abundances of compatible elements. Trace-element signatures show negative U, Th, Zr, Ti and Pb and positive Sr, Ba and Eu anomalies with respect to the primitive mantle. The chondrite-normalized diagram shows strongly fractionated rare earth element patterns ((La/Lu)N ∼23–87). Geochemical fingerprints suggest that the basanitic protolith was formed by low-degree partial melting of garnet peridotite in the sub-continental lithospheric mantle. The enriched large ion lithophile, high field strength element and light rare earth element concentrations (relative to primitive mantle) can be explained by a mixed mantle source with components from a previously deformed alkaline rock/carbonatite. Geochemical data do not support any significant crustal contamination and suggest variable fractionation of clinopyroxene, ilmenite, titanite and apatite from the parental melt. Petrological data are consistent with the view that the nepheline syenite magma was emplaced in a rift setting with a minimum temperature of 800–900°C, low fO2 conditions (below the fayalite–magnetite–quartz buffer) at a mid-crustal depth between 950 and 900 Ma. The continental rift zone, however, did not lead to the formation of an open ocean basin. Subsequently, the studied rock and its basement was deformed and metamorphosed in a continent–continent collisional setting at ∼900 Ma. Combining information from the other Indian occurrences with this study, it is demonstrated that the deformed alkaline rocks and carbonatite are potentially valuable for tracing the birth and demise of the palaeo-supercontinents.

Exploratory Seismic Geophysical Study of the Khanuqah Structure Area

Khanuqah structure area carried as the geophysics exploration study of Jeribe Formation target, the area located in the north of Iraq within Salah Aldeen Governorate, has been used geophysical data represented by 2D seismic lines were executed as exploratory surveys of 27 seismic lines, the data interpretations used by Petrel software (version 2018) based on the required aims, which are determined to achieve an update the structural model in Jeribe Fn. as a gas reservoir.The results show the Khanaqah structure includes five domes, the general direction of the structure axis is northwest-southeast, a gradient of its slope from the northwest structurally higher to the southwestern part structurally lower, the southeastern part of the study area is an open basin that increases the level of depth lines relative to the mentioned part.Seismic sections showed at the locations of structural domes the phenomenon of inter-spacing of seismic reflectors as tuning phenomena in reservoirs within Jeribe Fn. reservoir which is a direct index of the gas presence. To ensure tracking of extensions phenomena as a director for a gas presence, the seismic interpretations used a new technique by convert 2D seismic lines to 3D seismic cube through the reflections specifications publication of the khanaqah area, that shows the concerning of gaseous presence in the Khanaouqa-1 well and its disappearance in the Khanaouqa-2 well, it indicates the relationship between the location of the two wells at the structure, since Khanaouqa-1 well is structurally shallower than the Khanaouqa-2 well, which means that the well of Khanaouqa-2 is outside the scope of the gas patch, this was confirmed by the 3D seismic cube derived that showed the phenomenon presence on the site of Khanoqa-1 and did not appear in Khanoqa-2.Due to the importance of developing the Khanuqah structure as a worthy gas field, the research recommended drilling an exploratory well at the location of dome- B, whose coordinated in the study area penetrating the Euphrates Fn. bearing in mind that Khanuqa-1 did not locate on the center site of the domes nor on the center site of the direct phenomenon as evidence of the gas existence.

Particle fluxes in submarine canyons along a sediment-starved continental margin and in the adjacent open slope and basin in the SW Mediterranean Sea

Investigating the transfer of particulate matter from the continental shelf to the deep basin is critical to understand the functioning of deep sea ecosystems. In this paper we present novel results on the temporal variability of particle fluxes to the deep in three physiographic domains of a 240 km long margin segment and nearby basin off Murcia and Almeria provinces in the SW Mediterranean Sea, which are submarine canyons forming a rather diverse set (namely Escombreras, Garrucha-Almanzora and Almeria), the adjacent open slope and the deep basin.This margin is located off one of the driest regions in Europe and, therefore, its study may help understanding how mainland aridity translates into the export of particles to deep margin environments. Five mooring lines equipped with currentmeters, turbidity-meters and sediment traps were deployed for one entire annual cycle, from March 2015 to March 2016. We combine oceanographic, hydrological and meteorological data with grain size and bulk elemental data (organic carbon, opal, CaCO3, lithogenic) from the collected sinking particles to understand what drives particle transfers in such an under-studied setting, and to quantify the resulting fluxes and assess their spatio-temporal variability.Weighted total mass fluxes in canyons range from 1.64 g m−2 d−1 in Almeria Canyon to 7.33 g m−2 d−1 in Garrucha-Almanzora Canyon system, which are rather low values compared to other submarine canyons in the Western Mediterranean Sea. This results from the absence of extreme wind-storm events during the investigated time period combined with the reduced sediment input to the inner shelf by river systems in the study area. Our results also show that wind-storms are the main trigger for off-shelf particle transport to the deep margin, both within submarine canyons and over the open slope. The most significant transfer period is associated to a set of north-eastern storms in early spring 2015, when the off-shelf transport likely was promoted by storm-induced downwelling. However, the prevailing oceanographic conditions restricts the advection of water down the canyon heads to a few hundred meters, thus promoting a bottom-detached transport of particles seaward. Overall physiography, canyon head incision into the continental shelf and the distance of the canyon head to the shoreline (e.g. very short in Garrucha Canyon) play a key role in particle trapping capability and, therefore, in easing downslope particle transport. Further, bottom trawling activities around the Garrucha-Almanzora Canyon system, feed a nepheloid layer at depths in excess of 400 m, subsequently enhancing particle fluxes throughout the study period. In contrast, maximum particle fluxes in the deep basin respond to seasonal phytoplankton blooms.Our study shows that particle export from the shallow inner margin to the deep outer margin in sediment-starved settings, even if limited, does occur as dominated by atmosphere and ocean driven short-lived events. However, that export does not reach too far as at several tens of kilometres from the shelf edge advective fluxes are replaced by vertical ones impelled by phytoplankton dynamics.

A review of the morphology, physical processes and deposits of modern straits

AbstractThis study reviews the morphology, hydrodynamics and sedimentology of 33 modern straits, including examples from diverse tectonic and climatic settings. Strait morphology ranges from short, simple straits to long, tortuous passages many hundreds of kilometres long; depths range from 10 m to >1 km. The morphological building block of strait sedimentation is a constriction flanked by open basins; a single strait can contain one or several of these. Currents accelerate through the constrictions and decelerate in the basins, leading to a spatial alternation of high- and low-energy conditions. Currents in a strait can be classified as either ‘persistent’ (oceanic currents or density-driven circulation) or ‘intermittent’ (tidally or meteorologically generated currents). Constrictions tend to be bedload partings, with the development of transport paths that diverge outward. Deposition occurs where the flow decelerates, generating paired subaqueous ‘constriction-related deltas’ that can be of unequal size. Cross-bedding predominates in high-energy settings; muddy sediment waves and contourite drifts are present in some straits. In shallow straits that were exposed during the sea-level lowstand, strait deposits typically occur near or at the maximum flooding surface, and can overlie estuarine and fluvial deposits. The most energetic deposits need not occur at the time of maximum inundation.

Constraints on the uncertainty, timing, and magnitude of potential Mars oceans from topographic deformation models

Proposed ocean paleoshorelines on Mars have faced criticism over their genetic interpretation and because they deviate significantly from an expected equipotential surface (by many kilometers). Multiple geophysical deformation models have been proposed to explain this large topographic range and deviation including true polar wander and direct Tharsis-induced deformation. Yet, the application of these models is potentially flawed as there exists no consensus on exactly where these proposed paleoshorelines are located. Here, we apply these models to proposed maps and mappings of the putative martian ocean shorelines and show that even when considering deformation due to the rise of Tharsis and its associated true polar wander, the observed deviation within each Arabia level's paleotopography precludes them as past equipotential surfaces. Additionally, we compute best-fit ages for all proposed paleoshorelines relative to the rise of Tharsis and the ages span nearly the entire period of Tharsis construction. Assessment of the paleoelevations of open basin deltas and valley network termini also suggests disagreement with the timing of such features with a paleoocean. Overall, we find that these geophysical deformation models are unable to explain the large elevation ranges observed in the putative shoreline data and that the long-wavelength trends may simply be the result of mismapped features along the topographic dichotomy which itself may have been modified by Tharsis and/or true polar wander.

Response of planktonic diatoms to eutrophication in Nyanza Gulf of Lake Victoria, Kenya

In recent decades, the planktonic diatom community in central Lake Victoria changed from dominance of Aulacoseira species (mainly African endemic A. agassizii, A. nyassensis) to dominance of long needle shaped Nitzschia (often referred to as N. acicularis). This shift was referred to be caused by eutrophication, resulting in increased growth of diatom taxa with reduced requirement of silica in open water. In contrast, in the large shallow Nyanza Gulf A. granulata and A. granulata var. angustissima remained abundant, probably because of increased turbidity and nutrient availability. In this study, from July 2017 to July 2018, the planktonic diatom community composition was investigated monthly at three sampling stations in Nyanza Gulf, i.e. West Gulf (WG, located close to the open basin via Mbita channel), Mid Gulf (MG, central part of the Gulf) and East Gulf (EG, located most closely to Kisumu bay). A significant gradient in water quality conditions was observed along distance of 60 km from the main basin, i.e. the water transparency decreased from 0.8–1.2 m to 0.2–0.5 m while suspended solids increased from 3.3–9.8 mg/L to 12–63.8 mg/L. In total 19 common diatom morphospecies were documented and related to the gradient in trophic state. At WG, A. granulata and A. granulata var. angustissima formed diatom blooms or co-occurred with long needle shaped Nitzschia species such as N. kavirondoensis, N. lacustris, N. nyassensis, N. rusingae, Synedra cunningtonii, as well as Cyclostephanos malawiensis, C. damasii and Urosolenia victoriae indicating more oligotrophic conditions closer to the main basin. In the inner Gulf A. granulata (var. angustissima) and N. cf. fonticola var. pelagica possibly living epiphytically on the colony-forming cyanobacterium Microcystis aeruginosa dominated. In contrast to N. cf. fonticola var. pelagica, however, Aulacoseira spp. biovolume was found negatively related to Microcystis biovolume implying its suppression under Microcystis bloom conditions.

Dynamic Wake Identification for Model-and Full-Scale Container Ship

Propeller performance prediction is traditionally based on open water calm model basin tests. In waves, and during vessel manoeuvring, inflow to the propeller changes signifi-cantly, i.e. the shape of the wake field will change and propeller load and efficiency are impacted. This paper focus on the changes in wake fraction that can be identified in dynamic conditions. The effects on wake fraction of ship maneuvering and the effects of waves’ orbital velocity are investigated from experimental data. Model basin tests with a free sailing container ship model provide data for identification of propeller load and mean wake fraction during manoeuvring and during passage of waves. The results are verified with analysis during maneuvering in calm sea with a scale model and with the full-scale version of a 45.000 m3 container ship. Experimental results show the wake fraction variation during maneuvering, and estimates of wake fraction derivatives are found with respect to the relative sway velocity at the propeller. The contribution of the paper is to provide evidence for the magnitude of propeller shaft loads that can be expected during passage in a seaway and during manoeuvring.

The sedimentary response of mixed lithoclastic-bioclastic Lower- Pleistocene shallow-marine systems to tides and waves in the south Apennine foredeep (Basilicata, southern Italy)Tidalites Field Trips Special Volume - Tidalites, Matera, Field Trip T3

This two-day-long field trip is associated with the 10th International Congress of Tidal Sedimentology (Tidalites), Matera, Italy. The foreland-basin system of southern Italy preserves mixed lithoclastic-bioclastic deposits mostly accumulated in shallow-marine environments, reproducing types of mixing and degrees of segregation (sensu Chiarella and Longhitano, 2012; Chiarella et al., 2017) that are thought to be indicative of a variety of geological processes, including surficial waves and tides, acting at different time scales.During the Late Pliocene and Early Pleistocene, small open piggyback basins reproduced marginal-marine settings with various hydrodynamic conditions in the wedge-top depozone. Siliciclastic-bioclastic sediments accumulated under the influence of geomorphological elements, such as coastal sheltering, promontories, presence of tectonic highs and local inlets, hosting shoreface to offshore-transition zones, whose cross-stratified facies indicate how sensitive shallow-water mixed systems are to recording surficial waves and weak tidal currents.Along the outer-foredeep depozone, carbonate-bioclastic coastal wedges back-stepped over the gently sloping rocky flanks of a structural high, leading to the retrogradational stacking of seismic-scale prograding bodies. Their size and cross-sectional outcrop views apparently resemble those typical of large tidal sand waves developed in wide tide-dominated oceans. In contrast, internal facies features reveal the dominance of surficial waves and gravity-driven avalanches along clinoform depositional slopes, and a very negligible to no tidal influence.

Multiscale Enhanced Sampling Using Machine Learning.

Multiscale enhanced sampling (MSES) allows for an enhanced sampling of all-atom protein structures by coupling with the accelerated dynamics of the associated coarse-grained (CG) model. In this paper, we propose an MSES extension to replace the CG model with the dynamics on the reduced subspace generated by a machine learning approach, the variational autoencoder (VAE). The molecular dynamic (MD) trajectories of the ribose-binding protein (RBP) in both the closed and open forms were used as the input by extracting the inter-residue distances as the structural features in order to train the VAE model, allowing the encoded latent layer to characterize the difference in the structural dynamics of the closed and open forms. The interpolated data characterizing the RBP structural change in between the closed and open forms were thus efficiently generated in the low-dimensional latent space of the VAE, which was then decoded into the time-series data of the inter-residue distances and was useful for driving the structural sampling at an atomistic resolution via the MSES scheme. The free energy surfaces on the latent space demonstrated the refinement of the generated data that had a single basin into the simulated data containing two closed and open basins, thus illustrating the usefulness of the MD simulation together with the molecular mechanics force field in recovering the correct structural ensemble.

Using Convolutional Neural Networks for Detection and Morphometric Analysis of Carolina Bays from Publicly Available Digital Elevation Models

Carolina Bays are oriented and sandy-rimmed depressions that are ubiquitous throughout the Atlantic Coastal Plain (ACP). Their origin has been a highly debated topic since the 1800s and remains unsolved. Past population estimates of Carolina Bays have varied vastly, ranging between as few as 10,000 to as many as 500,000. With such a large uncertainty around the actual population size, mapping these enigmatic features is a problem that requires an automated detection scheme. Using publicly available LiDAR-derived digital elevation models (DEMs) of the ACP as training images, various types of convolutional neural networks (CNNs) were trained to detect Carolina bays. The detection results were assessed for accuracy and scalability, as well as analyzed for various morphologic, land-use and land cover, and hydrologic characteristics. Overall, the detector found over 23,000 Carolina Bays from southern New Jersey to northern Florida, with highest densities along interfluves. Carolina Bays in Delmarva were found to be smaller and shallower than Bays in the southeastern ACP. At least a third of Carolina Bays have been converted to agricultural lands and almost half of all Carolina Bays are forested. Few Carolina Bays are classified as open water basins, yet almost all of the detected Bays were within 2 km of a water body. In addition, field investigations based upon detection results were performed to describe the sedimentology of Carolina Bays. Sedimentological investigations showed that Bays typically have 1.5 m to 2.5 m thick sand rims that show a gradient in texture, with coarser sand at the bottom and finer sand and silt towards the top. Their basins were found to be 0.5 m to 2 m thick and showed a mix of clayey, silty, and sandy deposits. Last, the results compiled during this study were compared to similar depressional features (i.e., playa-lunette systems) to pinpoint any similarities in origin processes. Altogether, this study shows that CNNs are valuable tools for automated geomorphic feature detection and can lead to new insights when coupled with various forms of remotely sensed and field-based datasets.

Contribution of foraminifers in biostratigraphy and paleoecology interpretations of the basal Eocene from the phosphatic Sra Ouertaine basin, in the southern Tethys(Tunisia)

Micropaleontological, sedimentological and statistical studies were carried out on the late Paleocene-early Eocene succession of Sra Ouertaine and Dyr El Kef in Northern open phosphatic Basin of Tunisia. Based on the abundance and stratigraphic distribution of planktic foraminiferal species, five planktic zones have been recognized from the base to the top of the phosphatic layers. The El Acarinina sibaiyaensis Zone, the E2 Pseudohastigerina wilcoxensis Zone, the E3 Morozovella marginodentata Zone, the E4 Morozovella formosa Zones and the E5 Morozovella subbotinae Zone. The placement of Paleocene-Eocene boundary (PETM) is just below the base of the phosphatic interval. The ETM-2 event may be detectable in the analyzed biotic record of Sra Ouertaine.Based on benthic assemblages, abundances, cluster and multivariate statistical analyses, two biofacies were recognized for each section. The recognized ecozones are typical of warm and shallow water inner neritic setting (dominance of epifaunal fauna Anomalinoides, Dentalina and Cibicidoides associated with Frondicularia phosphatica, Trochamminoides globigeriniformis and Eponides elevatus). The paleoenvironment is eutrophic (presence of several bolivinitids and verneuilinids). For the Dyr El Kef section and P5 and E2 of Sra Ouertaine section, our records indicate that paleoenvironment is influenced by coastal upwelling without oxygen-deficiency, the paleodepth is estimated to be around 50 m. The paleoecosystem is diversified and balanced with a general tendency to stressed condition. While the upper part of Sra Ouertaine section is more eutrophic, influenced by coastal upwelling with oxygen-deficiency, the paleodepth is estimated to be less than 50 m and the ecosystem is unsettled.

Pollen productivity estimates strongly depend on assumed pollen dispersal II: Extending the ERV model

Pollen productivity estimates (PPEs) are a key parameter for quantitative land-cover reconstructions from pollen data. PPEs are commonly estimated using modern pollen-vegetation data sets and the extended R-value (ERV) model. Prominent discrepancies in the existing studies question the reliability of the approach. We here propose an implementation of the ERV model in the R environment for statistical computing, which allows for simplified application and testing. Using simulated pollen-vegetation data sets, we explore sensitivity of ERV application to (1) number of sites, (2) vegetation structure, (3) basin size, (4) noise in the data, and (5) dispersal model selection. The simulations show that noise in the (pollen) data and dispersal model selection are critical factors in ERV application. Pollen count errors imply prominent PPE errors mainly for taxa with low counts, usually low pollen producers. Applied with an unsuited dispersal model, ERV tends to produce wrong PPEs for additional taxa. In a comparison of the still widely applied Prentice model and a Lagrangian stochastic model (LSM), errors are highest for taxa with high and low fall speed of pollen. The errors reflect the too high influence of fall speed in the Prentice model. ERV studies often use local scale pollen data from for example, moss polsters. Describing pollen dispersal on his local scale is particularly complex due to a range of disturbing factors, including differential release height. Considering the importance of the dispersal model in the approach, and the very large uncertainties in dispersal on short distance, we advise to carry out ERV studies with pollen data from open areas or basins that lack local pollen deposition of the taxa of interest.

Geochemistry and paleogeographic implications of Permo-Triassic metasedimentary cover from the Tauern Window (Eastern Alps)

Abstract. The chemical composition of metasediments is a valuable source of paleogeographic information about the protolith's sedimentary environment. Here, we compile major- and trace-element whole-rock data, including B contents, and 10/11B-isotope ratios from the Permo-Triassic metasedimentary cover of the Pfitsch–Mörchner basin, overlying the Variscan basement in the western Tauern Window, Eastern Alps (Austria and Italy). The basement consists of orthogneiss (“Zentralgneis”, metamorphosed Variscan granitoids with intrusion ages between 305 and 280 Ma), and the roof pendant consists of granites (amphibolites, paragneiss, and minor serpentinites). The Zentralgneis is partly hydrothermally altered into pyrite quartzite with high Al–S contents, low Na–Sr–Ca–Mg contents, and very strong depletion of the light rare earth elements. Comparison with published detailed mapping of this and other time-equivalent basins in the western Tauern Window, with radiometric age data in the literature, and with unmetamorphosed basins in the South Alpine realm yields a late Permian to Early Triassic age of sedimentation. Although during Alpine metamorphism all rocks were strongly deformed, the whole-rock chemical compositions of the metasediments were not pervasively changed during deformation. We show that the sediments were deposited in a small, probably lacustrine–fluviatile, intramontane basin, under arid to semi-arid climatic conditions. The sequence starts with metaconglomerates, which can be interpreted as a mixture of the different basement rocks, based on a combination of major-element ratios Na2O / (Na2O + K2O) and MgO / (MgO + Fe2O3) with concentrations of trace elements Cr, V, and Ni. The sequence is overlain by a fining-upwards sequence of clastic sediments, in which the behavior of K, Rb, and Sr allows the reconstruction of intense diagenetic K–B metasomatism, which raised the K2O contents up to ∼ 10 wt %. The average B content of 218 µg g−1 is well above the B content of common sediments, and the B-isotope composition reaches extremely low values of down to −33 ‰ δ11B. The top of the sequence is a lazulite quartzite, interpreted as a former conglomeratic phosphatic sandstone, which marks the transition from a closed Permian basin to an open Triassic basin. Within the clastic sequence, the presence of hydrothermal tourmalinite veins documents a hydrothermal event after deposition but before the onset of Alpine metamorphism. A metamorphosed mafic dike swarm in the orthogneiss indicates a post-Variscan event of basaltic magmatism, and this event is tentatively correlated with increased heat flow in the Triassic basin and hydrothermal activity. A consistent conceptual model of this basin and its diagenetic modifications, based on a combination of geochemical data with petrographical and field information, provides the geodynamic context of the European margin at the onset of the Alpine orogeny.

Predicting the Depositional Environments of Mishrif Formation from Seismic Isopach Map in the Dujaila Oil Field, Southeast-Iraq

In this paper, we attempt to predict the depositional environments with associated lithofacies of the main reservoir of the late Cretaceous Mishrif carbonate Formation, depending on the analysis of the created seismic isopach map by integrating seismic and well data. The isopach map was created from a 3D-seismic reflection survey carried out at the Dujaila oil field in southeastern Iraq, which is of an area of 602.26 Km2, and integrated with the data of the two explored wells. Based on the interpretation of the seismic isopach map, the diagram of the 3D-depositional environment model of Mishrif Formation was constructed. It showed three distinguished depositional environments, which were graduated from a back reef lithofacies of a shallow open marine (shelf) environment in the west and NW, to a shoal environment of isolated Rudist reefal buildup in the middle, and a fore reef lithofacies of the deep open marine basin environment in the SE of the field. A 3D-instantaneous frequency model was generated to verify the capability of the seismic isopach map of predicting the depositional environments, which in turn showed that the low frequency was restricted in the region of the high thickness of Rudist reefal buildups (porous reservoir facies) in the vicinity of the productive well Dujaila-1.

Water Discharge Management Based on Open and Closed Cylinders in the Gravitation Water Vortex Power Plant

A Gravitation Water Vortex Power Plant (GWVPP) tool has been made to determine how much water flow is needed to generate electricity. This research was conducted by changing the flow rate and water pressure to determine the effect on the performance of a vortex power plant, and in previous studies, no one has made changes to the discharge and water pressure. The type of basin position used in this study is an open basin position and a closed basin position. Based on the advantages and disadvantages of each type of blade used, a study was carried out using the type of turbine blade model L by changing the water flow rate and water pressure at a predetermined position to determine the effect of water discharge and pressure on the turbine rotational speed. From the results of testing the water discharge measurement in a closed basin which is carried out on the addition of each flow of water discharge at the angle of the faucet 0o to 90o with a volume (V) 98 L and time (t) 1.11 minutes to 2.5 minutes, it can be seen that the average discharge value (Q) the resulting 81.08 l / s. and from the results of testing the water discharge measurement in the open basin which is carried out to the addition of each flow of water discharge at the angle of the faucet 0o to 90o with a volume (V) 98 L and time (t) 1.28 minutes to 4.1 minutes it can be seen that the average discharge value (Q ) resulting in 65.21 l / s.

Stratigraphic Scheme of Cambrian Deposits, South of the Cis-Yenisei Area of West Siberia

Abstract ––In this paper we present a stratigraphic scheme for the subdivision and correlation of the Cambrian deposits in the south of the cis-Yenisei area of West Siberia, which was adopted as a current scheme by the decision of the Interdepartmental Stratigraphic Committee in 2018. This scheme is based on the data from stratigraphic test wells (Lemok-1, Averinskaya-150, Tyiskaya-1, Vostok-1, Vostok-3, Vostok-4, etс.). In the study area, two structure-facies zones were identified: Kas (Lemok-1, Averinskaya-150, Tyiskaya-1, Vostok-4, and Eloguiskaya-1 wells), where sedimentary complexes accumulated in a salt subbasin, and Ket’ (Vostok-1 and Vostok-3 wells) with the deposition in an open sea basin. The boundary between these structure-facies zones is drawn along the inferred N–S-trending barrier reef zone. The rubrication in this paper is compiled in accordance with the requirements of the Stratigraphic Code of Russia for explanatory notes for regional stratigraphic schemes. Local stratigraphic subdivisions (formations, strata) are described and compared with the adjacent Turukhansk–Irkutsk–Olekma facies region of the Siberian Platform.

Disentangling magnetic and environmental signatures of sedimentary 10Be/9Be records

Reconstructions of the global production rate of the cosmogenic isotope 10Be from sedimentary records of authigenic 10Be/9Be ratios have been successfully used to obtain independent estimates of geomagnetic dipole moment variations caused by field excursions or reversals. In this study, we assess the reliability of 10Be/9Be as a proxy for the cosmogenic 10Be production rate by evaluating two potential biasing sources represented by sediment composition and climatic modulation. For this purpose, we compare five high-resolution 10Be/9Be records of the Matuyama-Brunhes (M-B) field reversal from sediment cores of the Indian, West Pacific, and North Atlantic oceans. Significant increase of 10Be/9Be ratios at ∼774 ka is explained in terms of the dominant control of geomagnetic modulation during the M-B reversal. Results do not support the existence of a direct proportionality between measured sedimentary 10Be/9Be ratio and cosmogenic 10Be production rate, as shown by 10Be/9Be records that offset relative to each other during and outside the M-B reversal.Residual differences between offset-corrected rescaled records do not appear to be related to an incomplete correction of variable sediment scavenging efficiencies by 9Be normalization. Instead, these differences can be explained by a common climatic modulation model, assuming a linear relation between 10Be/9Be and the global 10Be production rate with site- and time-dependent additive and multiplicative coefficients. These coefficients are linear functions of a single global climate proxy identified with the benthic δ18O record. Additive coefficients are almost constant in time and can represent up to ∼60% of the average 10Be/9Be value during periods of stable field polarity. Multiplicative coefficients are also site-specific, with mean values representing the bulk scavenging efficiency of the site, and variations about this mean expressing a multiplicative climatic modulation of the 10Be production rate. The amplitude of this modulation amounts to 10–15% of the maximum variations recorded during the M-B reversal and is sufficiently large to mask minor variations of the dipole moment during stable polarity periods. Reconstructions of the geomagnetic dipole intensity can benefit from the information about climatic modulation effects gained with our modelling approach. Best suited sites for magnetic field reconstructions should be characterized by minimal Be-recycling contributions from ancient 10Be reservoirs and minimal climatic modulation, as far as it can be determined from relative comparisons with other records. These conditions are most likely encountered in open basins at sites (1) with < 2.8 km water depth, (2) > 200 km offshore, and (3) located underneath a large current system extending over regions with minimum terrigenous inputs. Scaling all records with respect to a chosen reference enables to produce 10Be/9Be stacks with reduced noise and short-term local environmental effects. Differences between stacks obtained in this manner highlight global climatic effects that need to be considered when generating calibrated reconstructions of the geomagnetic dipole moment.

Spatiotemporal evolution of single sandbodies controlled by allocyclicity and autocyclicity in the shallow-water braided river delta front of an open lacustrine basin

Abstract The spatial and temporal evolution of the sandbody architecture of shallow-water deltas in open lacustrine basins is controlled by the classification of allocyclicity and autocyclicity. On the southwestern margin of the Ordos Basin, a braided river system deposited a shallow-water delta in the Late Triassic Period. Based on the principle of sequence stratigraphy and the hierarchical analysis of reservoir architecture, the spatial and temporal evolution of individual sandbodies in the Chang 81 member of the Yanchang Formation in the Zhenbei Oilfield is interpreted by utilizing data from cores, wells and outcrops. The research ideas are as follows: large deposition scale architectural elements (first- to third-order cycles, as defined by Miall) of different sequence levels are affected by allocyclicity associated with changes in tectonic activity, provenance, and sea level, and small deposition scale architectural elements (fourth- to fifth-order cycles, as defined by Miall) of different sedimentary facies mainly consist of individual sandbodies that are affected by autocyclicity associated with lake-level changes caused by various river processes. Based on previous studies, the results are as follows. The sedimentary characteristics of shallow-water deltas have been verified by core and outcrop data. In addition, three ultrashort-term cycles are identified on the basis of boundary sequences and lithofacies’ sequences in the outcrop section of the Rui River, and three sedimentary evolution stages of the delta front are defined. Finally, according to well data, five types of architectural elements at the level of single sandbodies are identified. The vertical superimposition and lateral contact relationships of different architectural elements indicate that during the three sedimentary evolution stages, the hydrodynamics weakened, strengthened slightly, and finally weakened substantially. Among the 20 kinds of architectural element spatial combination patterns formed by single sandbodies, primary and secondary sandbodies have great potential for hosting remaining oil. In the process of architectural spatiotemporal evolution, the geometry and connectivity of the underwater distributary channel gradually weakened, and the spatial relationship between the underwater distributary channel and other architectural elements increased. This article proposes a new method for researching shallow-water deltas and has some guiding significance for exploiting the remaining oil in oil fields.