Facies Description Research Articles

3D Sedimentary Architecture of Sandy Braided River, Based on Outcrop, Unmanned Aerial Vehicle and Ground Penetrating Radar Data

Ground Penetrating Radar (GPR) is a geophysical method that uses antennas to transmit and receive high-frequency electromagnetic waves to detect the properties and distribution of materials in media. In this paper, geological observation, UAV detection and GPR technology are combined to study the recent sediments of the Yungang braided river study area in Datong. The application of the GPR technique to the description of fluvial facies and reservoir architecture and the development of geological models are discussed. The process of GPR detection technology and application includes three parts: GPR data acquisition, data processing and integrated interpretation of GPR data. The geological surface at different depths and scales can be identified by using different combinations of frequencies and antenna configurations during acquisition. Based on outcrop observation and lithofacies analysis, the Yandong Member of the Middle Jurassic Yungang Formation in the Datong Basin has been identified as a typical sandy braided river sedimentary system. The sandy braided river sandbody changes rapidly laterally, and the spatial distribution and internal structure of the reservoir are very complex, which has a very important impact on the migration and distribution of oil and gas as a reservoir. It is very important to make clear the characteristics of each architectural unit of the fluvial sand body and quantitatively characterize them. The architectural elements of the braided river sedimentary reservoir in the Datong-Yungang area can be divided into three types: Channel unit, bar unit and overbank assemblages. The geological radar response characteristics of different types of sedimentary units are summarized and their interfaces are identified. The channel sediments form a lens-shaped wave reflection with a flat at the top and convex-down at the bottom in the radar profile, and the angles of the radar reflection directional axes are different on both sides of the sedimentary interface. In the radar profile, the deposit of the unit bar is an upward convex reflection structure. The overbank siltation shows a weak amplitude parallel reflection structure. The flood plain sediments are distributed continuously and stably in the radar profile, showing weak reflection characteristics. Different sedimentary units are identified by GPR data and combined with Unmanned Aerial Vehicle (UAV) detection data, and the establishment of the field outcrop geological model is completed. The development pattern of the diara is clarified, and the swing and migration of the channel in different stages are identified.

Mineralogical Fingerprint of Iron Ore Tailings in Paraopeba River Bedload Sediments after the B1 Dam Failure in Brumadinho, MG (Brazil)

The study presents SEM-based automated mineralogy to distinguish between natural sediments and iron ore tailings deposits from the Paraopeba River, after the failure of B1 Dam in Brumadinho, Minas Gerais, Brazil. Samples were obtained from borehole cores drilled over channel bars and banks eight months after the failure. After preliminary facies description, sediments from 54 chosen intervals were subjected to density measurement, X-ray diffraction (XRD), SEM-based automated mineralogy (QEMSCAN) analysis and determination of geochemical major components. Hierarchical clustering analysis (HCA) and principal component analysis (PCA) revealed six main mineral associations governed by different contents and ratios of quartz, kaolinite and hematite. Natural sediments are predominantly composed of mineral associations containing kaolinite, quartz and quartz + hematite with density values ranging from 2.5 to 3.3 g/cm3. Tailings deposits have density values higher than 3.5 g/cm3 and are mainly composed of hematite with occasional occurrences of kaolinite + hematite. Because of geological complexity and historical terrain occupation and usage, geochemical anomalies are common in the Paraopeba River sediments. Our data suggests that mineralogical oriented studies should precede detailed geochemical investigations, to enhance the understanding of the source of such anomalies and the environmental jeopardy associated to the occurrence. In this sense, SEM-based mineralogy has an enormous potential in environment studies.

Physical and Mechanical characteristic relationships of Late-Cretaceous to Eocene reservoir rocks in the Maui, Maari and Manaia Fields, New Zealand

Constraint on the rock strength parameters within the subsurface is a fundamental requirement for accurate geomechanical modelling of aspects of reservoir stability and regional scale basin interactions. Insufficient rock strength data for offshore lithologies within the Taranaki Basin leads to a dependence on uncalibrated, empirical relationships applied in conjunction with wireline measurements for rock strength predictions. Use of these uncalibrated empirical relationships can lead to unreliable strength estimates, which reduces the confidence in geomechanical modelling and the subsequent solutions for the region.We conducted uniaxial and triaxial experiments on cores from offshore Taranaki reservoir rocks from 2000 to 4000 m depth to develop the first, calibrated, empirical rock strength relationships for reservoir rocks of the Taranaki Basin, using both grain size and porosity as input parameters. We show that grain size and porosity can be used as predictive tools for determining Hoek-Brown and Mohr-Coulomb failure criterion parameters for petroleum geomechanics. As mean grain diameter and porosity are the dominant control on rock strength, we infer that rock strength parameters within the Taranaki Basin will follow a similar spatial distribution as the reservoir sandstone facies, which are dominantly defined by grain size.We also show that the empirical relationships we developed with this dataset can be locally calibrated for other parts of the Taranaki basin, and indeed for other sandstones, such as the Buntsandstein from the Rhine Graben, France. Finally, we provide an approach by which grain size (+/− porosity) can be used to approximate the input parameters for the Hoek-Brown failure criterion in the absence of laboratory experiments. We propose, therefore, that the empirical relationships presented herein can be used to link facies descriptions with first-order estimates of mechanical properties at the basin scale.

Observation of Marine Areas (Çandarlı and Gökova Bays) and Their Biodiversity

This study aimed to investigate to determine the number and biodiversity of species (especially seaweed populations) in the Çandarlı and Gökova Bays. Çandarlı and Gökova Bays are defined as "Special Environmental Protection Area (SEPA)" by the Ministry of Environment and Forestry of the Republic of Turkey, Special Environmental Protection Agency Presidency. For this purpose, in the study, i) description of habitats and facies in the studied areas, ii) determination of the number and diversity of species, iii) retrieval of underwater photo recordings, operations were carried out. The approach of collecting these data in such a way as to make comparisons and comments, especially for the future, has been followed. The literature shows that the existing ecological conditions and habitat characteristics of the areas restricted to SEPA and fisheries are studied. Thus, a comprehensive database is developed that will be extremely useful in terms of future works. On the other hand, the studies carried out are particularly inadequate for marine algae (macroalgae) in the related areas. As a result of the study, a total of 316 taxa were identified and observed, including 192 marine algae (20 Cyanobacteria, 54 Phaeophyceae, 93 Rhodophyta, 25 Chlorophyta), 3 seagrasses, 70 invertebrates (9 Porifera, 13 Cnidaria, 2 Annelida, 19 Mollusca, 16 Arthropoda, 10 Echinodermata, 2 Tunicata) and 51 fish (2 Chondrichthyes, 49 Osteichthyes).

Variscan structures and their control on latest to post-Variscan basin architecture: insights from the westernmost Bohemian Massif and southeastern Germany

Abstract. The Bohemian Massif exposes structures and metamorphic rocks remnant from the Variscan orogeny in central Europe and is bordered by the Franconian Fault System (FFS) to the west. Across the FFS, Variscan units and structures are buried by Permo-Mesozoic sedimentary rocks. We integrate existing DEKORP 2D seismic reflection, well, and surface geological data with the newly acquired FRANKEN 2D seismic survey to investigate the possible westward continuation of Variscan tectonostratigraphic units and structures and their influence on latest to post-Variscan basin development. Subsurface Permo-Mesozoic stratigraphy is obtained from available wells and tied to seismic reflection profiles using a synthetic seismogram calculated from density and velocity logs. Below the sedimentary cover, three main basement units are identified using seismic facies descriptions that are compared with seismic reflection characteristics of exposed Variscan units east of the FFS. Our results show upper Paleozoic low-grade metasedimentary rocks and possible Variscan nappes bounded and transported by Variscan shear zones ca. 65 km west of the FFS. Basement seismic facies in the footwall of the Variscan shear zones are interpreted as Cadomian basement and overlaying Paleozoic sequences. We show that the location of normal fault-bounded latest to post-Variscan late Carboniferous–Permian basins are controlled by the geometry of underlying Variscan shear zones. Some of these late Carboniferous–Permian normal faults reactivated as steep reverse faults during the regional Upper Cretaceous inversion. Our results also highlight that reverse reactivation of normal faults gradually decreases west of the FFS.

Micro-XRF-inferred depositional history of the Orakei maar lake sediment sequence, Auckland, New Zealand

Lake sediment records offer insights into past climate and environmental changes. There are, however, few continuous lake sediment records from the Southern Hemisphere mid-latitudes that span the last glacial interval (LGI) and have the requisite chronological control and sampling resolution. Orakei maar paleolake in the Auckland Volcanic Field, New Zealand, is an exception, as it contains a high-resolution record of continuous lacustrine sedimentation from its formative phreatomagmatic eruption ~ 130 ka, until post-glacial sea-level rise breached the crater tuff rim and connected the lake to the sea ~ 9 ka. We used micro-XRF core scanning, dry bulk density, loss-on-ignition and visual facies descriptions to investigate the depositional history of Orakei maar lake as a response to regional and global drivers of climate change, and to erosional events in the lake catchment. The climate history of the lake was divided into six depositional phases: (I) Early warming with frequent in-wash events, followed by climate fluctuations coeval with marine isotope stages (MIS) 5e to mid-5c, (II) Warm, quiescent depositional conditions during mid-MIS 5c to 5a, (III) A colder, windier interval during MIS 4, (IV) Warmer conditions with dominantly autochthonous sedimentation during MIS 3, (V) Cold conditions followed by a slow temperature increase and the onset of sea-level rise during late MIS 2, (VI) Warm conditions that culminated in formation of a peat unit at the top of the Orakei lacustrine sediment sequence, which was terminated by an influx of massive marine muds into the basin at 9.75 ka. Comparison of the inferred climate evolution at Orakei with climate inferences from the global marine benthic MIS record during LGI shows general agreement, though inferred climate changes consistently occur earlier at Orakei than in the MIS. There is also general agreement in temperature changes inferred from the Orakei record and from other regional lake sediment records, but more detailed comparison requires additional proxy climate data such as pollen, organic geochemistry and biomarkers, to better understand discrepancies between some records. This study demonstrated the great potential of the Orakei record for paleoclimate inference and the applicability of micro-XRF core scanning data for addressing questions about paleoclimate and paleoenvironment. It also highlighted past intervals that require further study.

Discussion and application of thin-layer sand connectivity of outer front facies

In this paper, the microfacies of thin-layer sand of outer front facies are described by homogeneous unit thickness classification in the past, the plane distribution of single sand body and the connection relationship between different sand body types are roughly understood; From the two aspects of vertical single-stage thin-layer sand body identification and fine description of sedimentary facies belt map applying energy facies in plane microfacies, the outer front belt is divided into 6 types and 9 kinds of thin-layer sand combinations, the connectivity of sand bodies is clearer and the directionality is clearer. The application of research results not only deepens the geological understanding, but also guides the adjustment of water-driven scheme.

Sedimentology and stratigraphic architecture of a fluvial to shallow-marine succession: The Jurassic Dhruma Formation, Saudi Arabia

ABSTRACTThe interaction of fluvial, tidal, and wave processes in coastal and paralic environments gives rise to sedimentary successions with highly varied styles of facies architecture; these are determined by the morphology and evolutionary behavior of the range of coastal sub-environments, which may be difficult to diagnose in subsurface sedimentary successions with limited well control.This study presents depositional models to account for stratigraphic complexity in a subsurface fluvial to shallow-marine succession, the Middle Jurassic Dhruma Formation, Saudi Arabia. The study achieves the following: i) it examines and demonstrates sedimentary relationships between various fluvial, nearshore, and shallow-marine deposits, ii) it develops depositional models to account for the stratigraphic complexity inherent in fluvial to shallow-marine successions, and iii) it documents the sedimentology and the stratigraphic evolutionary patterns of the lower Dhruma Formation in the studied area of Saudi Arabia. The dataset comprises facies descriptions of 570 m of core from 14 wells, 77 representative core thin sections, 14 gamma-ray logs, and FMI image logs from 4 wells. These data are integrated with quantitative information from > 50 analogous systems from a wide range of modern and ancient settings, stored in a relational database. Stratigraphic correlations reveal the internal anatomy of the succession.Facies associations are representative of fluvial channels, intertidal flats, pedogenically modified supratidal flats or floodplains, river-influenced tidal bars, weakly storm-affected shoreface and offshore-transition zones, storm-dominated delta-front and prodelta settings, and an open-marine carbonate-dominated shelf. These sub-environments interacted in a complex way through space and time. The vertical succession of the studied interval records an overall transition from coastal-plain deposits at the base to marine deposits at the top. As such, the succession records a long-term transgressive, deepening-upward trend. However, this general trend is punctuated by repeated progradational events whereby coastal sand bodies of fluvial, wave, and tidal origin prograded basinward during stillstands to fill bays along a coastline. The nature of juxtaposition of neighboring sub-environments has resulted in a sedimentary record that is highly complex compared to that generated by morphologically simple shoreface systems that accumulate more regularly ordered stratal packages.

The characteristics of Carboniferous volcanic lithofacies and volcanic reservoirs of Ke‐Bai Fault Belt, northwestern Junggar Basin

The Ke‐Bai Fault Belt in northwestern Junggar Basin has gained robust insights and wide attention on large‐scale hydrocarbon discoveries in the Carboniferous volcanic rocks. The integrated analysis of wireline logs, image logs, core photographs, thin sections, and scanning electron microscope allows the description and interpretation of volcanic facies and volcanic reservoirs, as well as their responses to controlling factors. The results indicate that three types of lithology are identified based on cores, including volcanic rocks, followed by sedimentary rocks and metamorphic rocks. In addition, explosive facies, effusive facies, volcanic sedimentary facies, and sub‐volcanic facies are delineated according to spatial distribution, occurrence condition, and appearance characteristics of volcanic products. Furthermore, the characteristics of reservoir space (including pores and fractures) are analysed and described. Finally, the controls on the characteristics of volcanic reservoirs are revealed, including volcanic lithofacies, tectonic movements, and diagenesis.

Occurrence of drug target residues within decantation tank sediments: a good clue to assess their historical excretion?

This study investigated the potential of sediments accumulated in sewer systems to record human activities through the occurrence of drug target residues (DTR). The installation studied is 17 m deep underground decantation tank that traps the coarse fractions of a unitary sewer system (northern part of Orléans, France), collecting both stormwater and wastewater. The sediments deposited in this tank could constitute a nonesuch opportunity to study the historical evolution of illicit and licit drug consumption in the catchment, however, the deposition processes and the record of DTRs remain largely unknown at present. Five cores were acquired from 2015 to 2017. One hundred fifty-two sediment samples were extracted using a mixture of ultra-pure water:methanol (1:1) prior to analysis of the extracts by high-pressure liquid chromatography coupled to tandem mass spectrometry. Several classical sedimentological analyses such as total organic carbon, facies description and granulometry were also performed on these samples, in order to understand the most important factors (e.g., physico-chemical properties of the DTRs, solid type, assumed load in wastewater) impacting their deposition.The key role of the speciation of DTRs was highlighted by the higher contents in neutral and anionic DTRs in organic layers, whereas only cationic DTRs were found in mineral layers. The considerable modifications in the sediments’ properties, generated by distinct origins (i.e., stormwater or wastewater), are therefore the most important drivers that must be taken into account when back-calculating the historical patterns of drug consumption from their DTR concentrations in decantation tank sediments. Further research remains necessary to fully understand the deposition process, but this study provides new clues explaining these temporal evolutions.

Alternating wet and dry depositional environments recorded in the stratigraphy of Mount Sharp at Gale crater, Mars

AbstractThe Curiosity rover is exploring Hesperian-aged stratigraphy in Gale crater, Mars, where a transition from clay-bearing units to a layered sulfate-bearing unit has been interpreted to represent a major environmental transition of unknown character. We present the first description of key facies in the sulfate-bearing unit, recently observed in the distance by the rover, and propose a model for changes in depositional environments. Our results indicate a transition from lacustrine mudstones into thick aeolian deposits, topped by a major deflation surface, above which strata show architectures likely diagnostic of a subaqueous environment. This model offers a reference example of a depositional sequence for layered sulfate-bearing strata, which have been identified from orbit in other locations globally. It differs from the idea of a monotonic Hesperian climate change into long-term aridity on Mars and instead implies a period characterized by multiple transitions between sustained drier and wetter climates.

Types of the Cambrian platform margin mound-shoal complexes and their relationship with paleogeomorphology in Gucheng area, Tarim Basin, NW China

Based on the observation of outcrops and cores, thin section identification, restoration of paleogeomorphology by residual thickness method, fine description of seismic facies, etc., the coupling relationships between the development patterns of various types of Cambrian platform margin mound-shoal complexes and paleogeomorphology in the Gucheng area of Tarim Basin have been examined. The Cambrian platform margin mound-shoal complex is divided into mound base, mound core, mound front, mound back and mound flat microfacies, which are composed of dolomites of seven textures with facies indication. The different paleogeomorphology before the deposition of mound-shoal complex in each period was reconstructed, and three types of mound-shoal complex sedimentary models corresponding to the paleogeomorphologies of four stages were established: namely, the first stage of gentle slope symmetric accretion type, the second stage of steep slope asymmetric accretion type and the third and fourth stages of steep slope asymmetric progradation type. Their microfacies are respectively characterized by “mound base - mound back + (small) mound core + mound front - mound flat” symmetric vertical accretion structure, “mound base - (large) mound core + mound front - mound flat” asymmetric vertical accretion structure, “mound base - (small) mound core + mound front - mound flat” asymmetric lateral progradation structure. With most developed favorable reservoir facies belt, the steep slope asymmetric accretion type mound-shoal complex with the characteristics of “large mound and large shoal” is the exploration target for oil and gas reservoir.

Paleogeographic evolution of the southern Paraná Basin during the Late Permian and its relation to the Gondwanides

The end of the Permian marks an important change in the depositional context of the southwestern Gondwanan continent. These changes are related to the last invasion of the Panthalassa Ocean, and the posterior oceanic retreat and emplacement of desertic conditions. This paper provides a detailed paleogeographic evolution of the southern portion of the Paraná Basin, supported by facies descriptions, stratigraphic analysis, and U-Pb-Hf detrital zircon analysis (LA-ICP-MS). The studied interval records a large regression that was composed of three forced-regression pulses related to important facies shifts ascribed to the outer ramp, inner ramp, and arid continental systems. Provenance zircon UPb analysis in the inner ramp and continental arid climate deposits indicates that the main sediment source was the Brasiliano basement and the Gondwanides mountain ridge, situated to the west and south. The abrupt paleogeographic change related to the evolution of a system dominated by inner ramp to arid continental facies is compatible with the tectonic reorganization of the Paraná Basin close to the Permo-Triassic limit. Here we present a paleogeographic evolution model which adds new elements to better understand the great transgressive-regressive event that occurred in southwestern Gondwana during the late Permian.

Exposing the inside of the fine-grained siliciclastic tidal shelf deposits of the Alicia Formation, Tandilia Basin, during the Ediacaran anoxia in the Clymene Ocean

In this contribution we outline the outstanding attributes and inferred depositional controls for dark mudstones of the Alicia Formation (~570 Ma) in order to reveal the intrinsic characteristics of unknown Ediacaran marine depositional conditions into the basin. The Alicia Formation represents a continuous and undeformed ~150 m thick sequence in which nine siliciclastic lithofacies were accumulated controlled by the Clymene sea conditions. Sedimentary facies analysis of their fine-grained rocks reveals a deposition across two depositional sequences. The basal portion is described as formed in an upper offshore while the upper portion represents a lower shoreface environment. This study combines the stratigraphic characterization with detailed facies descriptions, petrography, XRD, SEM and geochemistry analyses. This succession was deposited under relatively constant marine environmental conditions with relative sea level variations manifested between the fair-weather and storm wave bases. Bottom-water conditions during its sedimentation show fluctuations in the geochemical indicators as redox-sensitives (U, Mo, V), terrigenous supply (Si, Al, Zr, Th), carbonate productivity (CaO) and organic productivity (Cu, Ni, P/Al). This research represents an exceptional example of preserved fine-grained Ediacaran tidal shelf deposits in the Tandilia Basin. The data provide evidence for the middle Ediacaran anoxia, which post-dates a previous oceanic oxygenation event (EOO, 580 Ma) and pre-dates the white sea assemblage radiation (560 Ma) probably developed in a well oxygenated sea. Within the SW Gondwana scenario, our findings may support a link between the depositional setting during most severe redox changes.

Sedimentation of the Kimmeridge Clay Formation in the Cleveland Basin (Yorkshire, UK)

Fine-grained sedimentary successions contain the most detailed record of past environmental conditions. High-resolution analyses of these successions yield important insights into sedimentary composition and depositional processes and are, therefore, required to contextualise and interpret geochemical data which are commonly used as palaeoclimate proxies. The Kimmeridge Clay Formation (KCF) is a 500 m-thick mudstone succession deposited throughout the North Sea in the Late Jurassic and records environmental conditions through this time. Here, we present petrographic analyses (on 36 thin sections) on a 50 m section of a KCF core from the Cleveland Basin (Yorkshire, UK) to investigate controls on sedimentation in this region during the Tithonian, Late Jurassic. Facies descriptions demonstrate that deposition took place in a hydrodynamically variable environment in which the sediment origins, sediment dispersal mechanisms, and redox conditions fluctuated on the scale of thousands of years. Petrographic analyses show that the sediment comprises marine (algal macerals, calcareous fossils), detrital (quartz, clay, feldspar), and diagenetic (dolomite and authigenic kaolinite) components and that several sediment dispersal mechanisms influenced deposition and facilitated both the supply and preservation of terrestrial and marine organic material. This work provides a framework for the interpretation of geochemical palaeoclimate proxies and reinforces the importance of looking at the rock when interpreting whole-rock geochemical data.

Early Sevier orogenic deformation exerted principal control on changes in depositional environment recorded by the Cretaceous Newark Canyon Formation

ABSTRACT Terrestrial sedimentary archives record critical information about environment and climate of the past, as well as provide insights into the style, timing, and magnitude of structural deformation in a region. The Cretaceous Newark Canyon Formation, located in central Nevada, USA, was deposited in the hinterland of the Sevier fold–thrust belt during the North American Cordilleran orogeny. While previous research has focused on the coarser-grained, fluvial components of the Newark Canyon Formation, the carbonate and finer-grained facies of this formation remain comparatively understudied. A more complete understanding of the Newark Canyon Formation provides insights into Cretaceous syndeformational deposition in the Central Nevada thrust belt, serves as a useful case study for deconvolving the influence of tectonic and climatic forces on sedimentation in both the North American Cordillera and other contractional orogens, and will provide a critical foundation upon which to build future paleoclimate and paleoaltimetry studies. We combine facies descriptions, stratigraphic measurements, and optical and cathodoluminescence petrography to develop a comprehensive depositional model for the Newark Canyon Formation. We identify six distinct facies that show that the Newark Canyon Formation evolved through four stages of deposition: 1) an anastomosing river system with palustrine interchannel areas, 2) a braided river system, 3) a balance-filled, carbonate-bearing lacustrine system, and 4) a second braided river system. Although climate undoubtedly played a role, we suggest that the deposition and coeval deformation of the synorogenic Newark Canyon Formation was in direct response to the construction of east-vergent contractional structures proximal to the type section. Comparison to other contemporary terrestrial sedimentary basins deposited in a variety of tectonic settings provides helpful insights into the influences of regional tectonics, regional and global climate, catchment characteristics, underlying lithologies, and subcrop geology in the preserved sedimentary record.

Reconstructing medieval eroded landscapes of the north-eastern Zuyder Zee (the Netherlands): a refined palaeogeographical time series of the Noordoostpolder between a.d. 1100 and 1400

ABSTRACT This paper considers large-scale erosion of late medieval peatland landscapes along the inland lagoon rims of the north-eastern Zuyder Zee area (today: Noordoostpolder, the Netherlands) and integrates palaeogeographical reconstruction, material archeological and spatial archaeohistorical research. The dynamic regional history of coeval loss of peaty coastal plains and boom of maritime activities is studied from archaeological, geological and historical data perspectives. In the first half of the Middle Ages (a.d. 500–1000), vast peatlands and interconnected lakes characterised the study area. During the late Middle Ages (a.d. 1000–1500), increased storm surges and tidal incursions allowed for extensive progressive erosion of inhabited peatlands, transforming the central Netherlands into the Zuyder Zee tidal lagoon. In the north-eastern quadrant of the expanding water body, medieval terrestrial geological and archaeological records fell prey to erosion, re-working and uptake into lagoon-floor deposits. These deposits have been intensively surveyed since the 1940s when the quadrant was reclaimed and made into arable land, and are revealed to contain spatially clustered late medieval archaeological objects. Whereas lagoon floor re-working has hindered making a detailed palaeogeographical reconstruction based on geological data alone, including the mapping of archaeology has helped resolve the pacing of lagoon expansion. The key to resolving the lost peatland palaeogeography for the time frames 1100 and 1400, was to put the archeological data density patterns first and geological lagoon-floor facies descriptions second in process order, while for earlier periods or other regions the opposite order is the convenient choice. We present a map series beginning with an updated map for a.d. 900 (the youngest geological reconstruction), introducing the first detailed palaeogeographical maps for 1100 and 1400 (honouring the late medieval terrestrial and maritime archaeological evidence) and ending with a landscape reconstruction for 1600 (complying with the oldest historical maps of the lagoon), revealing the intertwined landscape history of land and sea as the backdrop for shifts in the human use of both.

Facies, petrography, reservoir heterogeneity and quality of the late Carboniferous-Permian Juwayl Member, Wajid Sandstone, SW Saudi Arabia

The Paleozoic Wajid Sandstone in southwestern Saudi Arabia comprises four members known as Dibsiyah, Sanamah, Khusayyayn and Juwayl. The study characterizes the sedimentary facies of the Juwayl Member from five outcrop localities in Wadi Ad-Dawasir area. The objective is to reveal the influence of facies heterogeneity on the reservoir distribution and quality. The field investigations involve facies description, sampling and architectural elements identification. The second step involves the interpretation of facies associations to predict the depositional environments and controls. The petrographic analysis, of thin section, SEM and XRD, helped to define the diagenetic controls that affected the quality and heterogeneity of rock properties such as porosity and permeability. The facies analysis revealed ten lithofacies corresponding to glacio-fluvial and braided-fluvial depositional environments. The glacio-fluvial deposits consist of pebbly to conglomeratic sandstone lithofacies that suggest high to medium energy conditions within a proximal fluvial setting. The braided-fluvial deposits are of medium to coarse-grained, trough to planner cross-bedded sandstone lithofacies. These lithofacies indicate a lower energy distal condition of laterally switching channels. The remaining lithofacies include overbank deposits of fine-grained argillaceous-ferruginous sandstone lithofacies, observed at the top of fining upward sequences. The study classified Juwayl sandstone as mineralogically mature quartz arenite with good to very good porosity and permeability. It dominates by (90%) quartz, and other components of calcite, clay and iron oxides with subordinate K-feldspars. The diagenetic controls including cementation, grain-size reduction, quartz overgrowth and clay minerals are affecting the Juwayl sandstone porosity and permeability. The depositional environments of Juwayl sandstone indicate a system switching from high energy glacio-fluvial to lower energy braided-fluvial setting. The thickness and width of the sandstone bodies tend to vary in this model implying vertical and lateral sandstone heterogeneity. Clay, hematite and calcite cements contributed to porosity reduction, while grain dissolution, clay coats and rims contributed to porosity enhancement. Macro-scale outcrop heterogeneity in terms of facies, paleonvironments and stratigraphic architecture and microscopic scale in terms of texture, composition and diagenesis, all might provide guides for subsurface reservoir assessment, comparison and correlations.

Sedimentology, diagenesis, and reservoir characterization of the Permian White Rim Sandstone, southern Utah: Implications for carbon capture and sequestration potential

Rising CO2 emissions have caused scientists and policy makers to explore potential solutions to reduce atmospheric CO2 levels, including carbon capture and sequestration. This project, funded through the Department of Energy CarbonSAFE initiative, aims to characterize the potential storage capacity and preferential fluid-flow pathways through the Permian White Rim Sandstone on and near the San Rafael Swell, Utah, to assess the formation’s viability as a possible CO2 sequestration reservoir. A diverse suite of sedimentological observations and diagenetic analyses was used to assess the White Rim Sandstone’s reservoir potential, including detailed outcrop observations, facies descriptions and ichnology, measured stratigraphic sections with associated correlations, permeability measurements, thin-section petrography, and visible and near-infrared spectroscopy. Stratigraphically, the White Rim Sandstone has two major units separated by a marine transgressive surface. The lower eolian unit is characterized by decimeter- to meter-scale trough cross-bedded grain-flow and wind-ripple facies. The upper reworked, shallow-marine unit has a consistent set of facies at all three field sites: (1) soft-sediment deformation facies (e.g., contorted bedding or clastic pipes), (2) symmetric ripple laminations, (3) bioturbated (dominantly horizontal), and (4) bioturbated (dominantly vertical). This set of four facies represents the transgression of the Permian Kaibab sea over the Permian White Rim coastal dune field. The outcrop samples and subsurface core samples (∼1561–2243 m deep and ∼33–50 km away from the outcrop localities) experienced different diagenetic fluid-flow histories that drastically impacted the reservoir properties. Outcrop samples have initial quartz overgrowth cements followed by rim-forming calcite cements, iron oxide cements, and occasional oil staining. In contrast, the core samples show significant compaction, followed by quartz overgrowth cementation and a later stage of patchy, large, pore-filling calcite cement that eliminated the porosity and permeability of the potential reservoir (<0.1 md). Outcrop permeability values tend to reflect textural differences in facies, particularly the presence and spacing of internal laminations and bounding surfaces. Facies with fewer internal laminations, such as the grain-flow facies, have higher permeability values than facies with closely spaced internal laminae, such as the wind-ripple facies. Disruption of original bedding (e.g., soft-sediment deformation or bioturbation) alters original depositional textures and creates preferential flow pathways with the potential to increase permeability. Overall, if the diagenesis and resulting low permeability values of the core samples are representative of the White Rim Sandstone at depth, then the White Rim Sandstone would not make a high-quality storage reservoir despite initial, promising outcrop results.

FACIES ANALYSIS AND DEPOSITIONAL ENVIRONMENTS OF KURACHINE DOLOMITE FORMATION FOR NORTH DUBAISAN FIELD IN SYRIA

Background At the present stage of exploration and development of oil fields, reliable construction and updating of geological models require information on the facies of sedimentation, which determines the collector properties of the reservoirs and the conditions for the formation of oil and gas traps in them. The article briefly discusses the geological structure of the North Dubaisan oil field. A facial analysis was carried out on the area of the deposit in order to study in detail the sedimentary formations of the Kura-Chine Dolomite Formation, which consists in isolating facies and determining sedimentation conditions. Descriptions of sedimentary facies and sedimentation conditions are presented in many publications, including Brew G., Barazengi M., Al-Maleh KH., Sawaf T., Litak R., Al-imam A., Al-Youssef W., Al Kadi M., Mamita B., Shera T., Hadidi A. and others. Aims and Objectives Perform facial analysis on the basis of a comprehensive interpretation of log data, seismic sections, a detailed description of the core and petrophysical studies of rock samples, to predict the distribution and quality of productive reservoirs. Methods A sequential stratigraphic method for studying facies was used, which can significantly improve understanding of sedimentation conditions. This study uses data from the above sources, as well as data from the Syrian Oil Company, which uses a comprehensive interpretation of well logs and a detailed description of the core. Results The main results of the study are the identification of facies and the determination of sedimentation conditions of the North Dubaisan region, and their correlation. As a result of the studies, a combination of geological and geophysical studies was made that allows, based on lithological-facial, sequence-stratigraphic analysis and interpretation of well log data, to perform a detailed reliable analysis of the facial characteristics of the section, as well as to predict in the facies space in the intervals not characterized by core material.