Flooding Surface Research Articles

The heterogeneity of lithofacies types, combination modes, and sedimentary model of lacustrine shale restricted by high‐frequency sequence

The second Member of the Funing Formation in the Haian Sag of the Subei Basin is a set of organic‐rich fine‐grained sedimentary rocks, which is a key interval for shale oil exploration. Under the premise of establishing a high‐frequency sequence framework, the fine description of the lithofacies change characteristics of the continental fine‐grained sedimentary rocks is the basis for the prediction of shale oil favourable areas and the optimization of the production horizons. This study is established through wavelet transformation of the natural gamma curve of the high‐frequency sequence framework of the second Member of the Funing Formation, using thin‐section observation, total organic carbon analysis, and X‐ray diffraction experiments to study the lithofacies types and characteristics of fine‐grained sedimentary rocks, and discuss the combination of lithofacies under the high‐frequency sequence framework Mode and influencing factors. The results show that the second Member of Funing Formation is composed of three‐level sequence of low‐level system tract (LST), transgressive system tract (TST), and early high‐level system tract (EHST), corresponding to 6 fourth‐level sequences and 10 fifth‐level sequences. According to the division scheme of “abundance of organic matter + mineral composition + sedimentary structure”, it is found that 12 types of lithofacies were developed in the fine‐grained sedimentary rocks of the second Member of Funing Formation. The lithofacies type is affected by the palaeoenvironment. The organic matter facies are mainly controlled by palaeo‐water depth and palaeo‐redox conditions, the components are mainly controlled by palaeo‐water depth and palaeo‐salinity, and the tectonic facies are mainly controlled by palaeo‐redox and palaeo‐salinity. The lithofacies are regularly superimposed in the high‐frequency sequence framework, and three combination modes of A, B, and C are developed. Among them, the type A lithofacies are developed in the low‐stand system tract, and the type B lithofacies are developed in the transgressive system. The C‐type lithofacies assemblage developed near the largest flooding surface and the early highstand system tract, and combined with palaeoenvironment analysis to establish a lithofacies sedimentary model.

Concurrent 1. Presentation for: A regional chronostratigraphic framework for play-based resource assessments in the Eromanga Basin

Presented on Tuesday 17 May: Session 1 Geoscience Australia is undertaking a series of basin-scale assessments to identify the ‘yet-to-find’ resource potential for hydrocarbons, as well as for groundwater resources and carbon capture and storage (CCS) opportunities in central Australia under the Exploring for the Future (EFTF) Program. A play-based exploration approach is being used to systematically evaluate the key risk elements for each resource type through the analysis of drilling results and spatial data to map ‘sweet spots’ for exploration. These assessments aim to reduce the risks and uncertainties for explorers by providing spatially enabled assessments of energy resources and CCS potential. The work will also improve the understanding of existing groundwater resources which may be impacted by future energy resource developments or provide feedstock for future green hydrogen projects. A key requirement for undertaking such play-based resource assessments is to apply a common regional chronostratigraphic framework across all the resource types that link different geological unit nomenclatures through defining the assessed reservoir and seal intervals and their associated sequence stratigraphic surfaces (sequence boundaries, transgressive surfaces and maximum flooding surfaces). A Mesozoic chronostratigraphic framework has been developed for the Eromanga Basin, which defines nine regional play intervals that host the known hydrocarbon and groundwater resources, or represent potential CCS targets. The Mesozoic play framework is now being applied to undertake play-based low-carbon energy resource assessments in the western Eromanga Basin, with initial work focussing on the interpretation and correlation of the nine play intervals in wells for post-drill analysis. To access the presentation click the link on the right. To read the full paper click here

Biostratigraphy and paleoecology of the trilobite faunas from the Mount Clark and Mount Cap formations (early and middle Cambrian), eastern Mackenzie Mountains, northwestern Canada

AbstractLower and middle Cambrian strata of the eastern Mackenzie Mountains, Northwest Territories, Canada, were deposited in a semi-enclosed basin along the eastern flank of the Mackenzie Arch. The Mount Clark Formation is predominantly composed of nearshore sandstone and is overlain by deeper water siltstone, mudstone, and carbonates of the Mount Cap Formation. The contact between these formations is interpreted as a flooding surface. Trilobite biostratigraphy indicates the presence of the traditional upper Olenellus through Glossopleura zones (Cambrian Series 2, Stage 4–Miaolingian, Wuliuan) and suggests the flooding surface is diachronous, spanning the Dyeran-Delamaran boundary. Above the Olenellus Zone, the Amecephalus arrojosensis-Eokochaspis nodosa Zone, the new Aitkenaspis keelensis Zone, the new Albertelloides mischi Zone, and the Glossopleura walcotti Zone are recognized. Whereas the older zones are comparable to those in other areas of Laurentia, the trilobite faunas in the Albertelloides mischi and Glossopleura walcotti zones show a greater abundance of zacanthoidids and dolichometopids. They also have a lower diversity of ptychoparioids and oryctocephalids, and lack agnostoids, eodiscoids, dorypygids, and ogygopsidids. This suggests that zacanthoidids and dolichometopids were able to tolerate conditions that were unfavorable to the other groups, probably related to semi-restricted conditions in the basin. Four endemic species exhibit characteristics that are considered paedomorphic. This developmental process took place in three separate lineages, suggesting that heterochrony was also environmentally provoked.New taxonomic names are authored by Handkamer and Pratt. New genera are Eobathyuriscus, Sahtuia, Mexicaspidella Aitkenaspis, Dodoella, and Mackenzieaspis. New species are Bolbolenellus dodoensis, Eobathyuriscus mackenziensis, E. macqueeni, Glossopleura youngi, Sahtuia carcajouensis, Aitkenaspis keelensis, Albertelloides eliasi, Dodoella kobayashii, Mackenzieaspis parallelispinosa, and M. divergens.UUID: http://zoobank.org/a10a2470-853c-4ce8-bf62-7de1d2c99fab.

A mud-dominated coastal plain to lagoon with emerged carbonate mudbanks: The imprint of low-amplitude sea level cycles (mid-Upper Cretaceous, South Iberian Ramp)

The middle Santonian-lower Campanian carbonate-mud dominated succession deposited in the northeastern margin of the South Iberian Ramp (La Cañadilla Fm, NE Spain) shows a complex set of interfingered facies developed in a low-energy and low-gradient shallow-marine to coastal environment. Three facies belts characterize the environment reconstructed in this work: (1) a low-energy shallow marine lagoon dominated by radiolitid rudist limestones and miliolid-rich facies with variable carbonate-mud content; (2) a transitional belt with a patchy distribution of ponds and mudbanks. This belt mostly consists of miliolid-rich limestones with variable amount of fenestral porosity, which are interfingered with charophytes and gastropod marls and limestones usually mixed with miliolids; (3) a coastal plain with strong freshwater influence characterized by the sedimentation of marls and limestones with charophytes, gastropods and root traces and intraclastic/black pebble limestones. The studied succession is arranged in high-frequency sequences, including meter-scale parasequences bounded by widespread flooding surfaces, which stack in five larger-scale shallowing-upward sequences (6–20 m thick). The time calibration of these sequences obtained from strontium isotopes and biostratigraphic data (benthic foraminifera) suggests a major control in the sedimentation by climate-driven low-amplitude sea level oscillations formed in tune with the long- and short-eccentricity orbital cycles. Cyclic sea level rises controlled the existence of widespread flooding events in the low-gradient carbonate ramp at the onset of parasequences, which in the studied marginal areas of the South Iberian Ramp were mostly sourced from the southern Tethyan realm. Therefore, the La Cañadilla Fm provides an example of a complex shallow marine to coastal system giving rise to a mosaic distribution of carbonate-mud dominated facies, with sedimentation mostly influenced by external factors resulting in a well-defined stratigraphic architecture. The similarities with modern analogous systems such as the Ten Thousand Islands of the Florida Bay are discussed in this paper.

A regional chronostratigraphic framework for play-based resource assessments in the Eromanga Basin

Geoscience Australia is undertaking a series of basin-scale assessments to identify the ‘yet-to-find’ resource potential for hydrocarbons, as well as for groundwater resources and carbon capture and storage (CCS) opportunities in central Australia under the Exploring for the Future (EFTF) Program. A play-based exploration approach is being used to systematically evaluate the key risk elements for each resource type through the analysis of drilling results and spatial data to map ‘sweet spots’ for exploration. These assessments aim to reduce the risks and uncertainties for explorers by providing spatially enabled assessments of energy resources and CCS potential. The work will also improve the understanding of existing groundwater resources which may be impacted by future energy resource developments or provide feedstock for future green hydrogen projects. A key requirement for undertaking such play-based resource assessments is to apply a common regional chronostratigraphic framework across all the resource types that link different geological unit nomenclatures through defining the assessed reservoir and seal intervals and their associated sequence stratigraphic surfaces (sequence boundaries, transgressive surfaces and maximum flooding surfaces). A Mesozoic chronostratigraphic framework has been developed for the Eromanga Basin, which defines nine regional play intervals that host the known hydrocarbon and groundwater resources, or represent potential CCS targets. The Mesozoic play framework is now being applied to undertake play-based low-carbon energy resource assessments in the western Eromanga Basin, with initial work focussing on the interpretation and correlation of the nine play intervals in wells for post-drill analysis.

Biomarkers and PAH chemostratigraphy in the study of the Frasnian anoxic event in the Pimenteiras Formation outcrop of the Parnaíba Basin, Brazil

The Late Devonian is characterized by episodes of sea-level rise and expansion of dysoxic to anoxic paleoenvironments, resulting in a global abundance of organic-rich sedimentary rocks. These changes have been well documented in biostratigraphic studies of Euroamerica basins. However, the relationship between sea-level rise and marine anoxia in Western Gondwana sedimentary rocks is not completely understood. Here, biomarker and PAH diagnostic ratios were applied to investigate changing depositional paleoenvironment and organic matter inputs of the Pimenteiras Formation along the western edge of the Parnaíba Basin. First, 24 shale samples collected from 16 regionally distributed outcrops were analysed, revealing variability in depositional paleoenvironment conditions. Secondly, for detailed study a 15-m thick outcrop was chosen, from which 11 shale samples were collected. These samples were submitted to chemostratigraphic and palynostratigraphic analyses and their records were highlighted. Two sample groups were identified, one sample group containing mixed organic matter, predominantly terrigenous and with fresh-brackish water organisms, deposited under dysoxic conditions. The other sample group comprised mixed organic matter containing a high contribution of marine organisms, preserved under anoxic conditions. Results indicated a marine flooding surface in the Pimenteiras Formation Outcrop 1, associated with a Devonian transgressive event related to sea-level rise and probably to global anoxic conditions during the Frasnian in the Parnaíba Basin. In addition, it was possible to correlate the abundance of miospores Verrucosisporites genus with high Retene/Chrysene values, suggesting that these miospores can be associated with a biological precursor of retene.

Depositional facies and sequence architecture of the Yijianfang Formation in the Shuntuoguole Low Uplift, Tarim Basin, NW China

In the Middle Ordovician, a ramp carbonate platform was developed in the Shuntuoguole Low Uplift, Tarim Basin. The depositional facies and sequence stratigraphy were investigated using petrographic observations and Fischer plot analyses to clarify the evolution and distribution of depositional facies within the sequence stratigraphic framework of the Yijianfang Formation. Nine types of microfacies (MF1–MF9) were identified in seven environments on a ramp: (a) peritidal, (b) lagoon, (c) low‐energy bioclastic shoal, (d) shoal, (e) sheltered proximal middle‐ramp, (f) low‐energy bioclastic shoal middle‐ramp, and (g) shoal middle‐ramp. A depositional model was established based on analyses of the depositional facies from the key wells. Fischer plots obtained based on fourth‐order cycles identified from continuous wavelet transform of gamma‐ray logging data were analysed. The results show that the changes in relative sea level, as indicated by Fischer plots, are highly consistent with the evolution of paleo‐water depths indicated by microfacies types, microfacies associations, and geochemical indicators. Four third‐order depositional sequences (SQ1–4) were identified according to variations in accommodation space. The accommodation space and its growth rate during the SQ2 transgressive period were the largest, it manifested as rapid landward migration of facies, and sudden changes in the gamma‐ray logging values at the maximum flooding surface. This feature can be easily compared across the entire region. The results of this study indicate that changes in relative sealevel in the Yijianfang Formation are consistent with the global sea‐level change curve, which suggests that sea‐level fluctuation is the main factoir controlling sequence architecture and the evolution of depositional facies.

Scale, origin, and predictability of reservoir heterogeneities in shallow-marine carbonate sequences: A case from Cretaceous of Zagros, Iran

This study presents an integrated reservoir heterogeneity analysis of an Iranian carbonate oil reservoir (Sarvak Formation) in the Zagros region. Both static and dynamic aspects of reservoir heterogeneities are considered by integration of routine–special core data and geological attributes (i.e., depositional facies and textures, diagenetic alterations, pore types, and sequence stratigraphic positions). Core porosity and permeability, mercury injection capillary pressure, and scanning electron microscopy data are used along with the results of petrographic studies to define petrographic rock types, pore types, hydraulic flow units, and reservoir to non-reservoir (baffle or barrier) zones in the studied reservoir. Spatial facies distribution (facies variability) and development of disconformable surfaces (sequence boundaries) controlled the large-scale reservoir heterogeneities. On the other hand, variations in microscopic characteristics of depositional facies (i.e., textures and structures) and diagenetic features (e.g., intensity of dissolution, cementation and compaction) formed the small-scale reservoir heterogeneities. The best productive zones of this reservoir are meteorically-dissolved reef-talus and shoal facies, accumulated within the regressive systems tracts of third-order sequences. Intensively compacted and cemented facies formed the effective vertical barrier/baffle zones in this reservoir, especially within the transgressive systems tracts and around the maximum flooding surfaces. Results of this study revealed that the stratigraphic modified Lorenz plot (SMLP) is a useful tool for the discrimination of large-scale reservoir heterogeneities, while hydraulic flow units and Winland rock typing approaches are applicable for the identification of small-scale heterogeneities. This study indicated that the large-scale heterogeneities of carbonate reservoirs are predictable in a sequence stratigraphic framework, especially in the third-order scale. Such a heterogeneity model calibrated in the sequence stratigraphic framework provides a reliable basis for reservoir modeling of heterogeneous carbonate reservoirs in the field-to regional scales.

SEQUENCE STRATIGRAPHY, PALAEOGEOGRAPHY AND PETROLEUM PLAYS OF THE CENOMANIAN – TURONIAN SUCCESSION OF THE ARABIAN PLATE: AN UPDATED SYNTHESIS

In order to facilitate the search for new play concepts and exploration opportunities, a sequence stratigraphic synthesis of the Cenomanian–Turonian interval of the Arabian Plate has been compiled. The synthesis is based on published datasets which have been analysed within a temporal framework constrained by biostratigraphy and isotope stratigraphy. The high stratigraphic resolution allows the palaeogeography of the study area to be mapped within 3rd order depositional sequences, and the relative influence of eustacy and tectonics on basin development to be evaluated. This significantly improves the prediction of stratigraphic architecture and depositional morphology at the scale of the entire tectonic plate.Conceptual models informed by outcrop and subsurface observations have been applied to characterize the development of intrashelf basins in depositional settings that are either isolated from siliciclastics (symmetric intrashelf basin model) or influenced by siliciclastics (asymmetric intrashelf basin model). The application of a sequence stratigraphic model across regional well log transects facilitates an understanding of stratigraphic architecture and acts as an important control for the generation of a new suite of gross depositional environment (GDE) maps. These maps characterize the palaeogeography at a previously unprecedented resolution and scale during both periods of high relative sea level (maximum flooding surface and highstand systems tract) and low relative sea level (lowstand systems tract). The maps are complemented by sequence isopachs which reveal changes in accommodation through time and space.This approach helps characterize the preserved distribution and stratigraphic configuration of petroleum systems elements. In the Shilaif (UAE), Natih (Oman) and Sarvak (Iran) intrashelf basins, condensed, organic‐rich carbonate source rocks were deposited in restricted, anoxic conditions. These basins resulted from differential aggradation of the carbonate platform during the transgressive systems tract. Grainy, rudist‐debris –rich carbonate reservoir rocks developed along the margins of the intrashelf basins during highstand progradation. Claystones in the overlying sequence may form intraformational seals and were deposited during retrogradation of the shoreline associated with sea‐level rise.By contrast in the Najaf intrashelf basin (Iraq), there is a significant siliciclastic component sourced from the Arabian Shield. This influx resulted in a mixed carbonate‐siliciclastic ramp depositional system on the proximal, western margin of the basin, and an apparent absence of organic‐rich intervals within the central basin succession. Grainy carbonate reservoir rocks are restricted to the eastern margin and are charged by older source rocks within the underlying stratigraphy.The GDE maps record the configuration of these petroleum systems elements within the Cenomanian–Turonian interval and form the basis for play screening. The Cenomanian–Turonian interval is punctuated by the major mid‐Turonian unconformity which is a tectonostratigraphic boundary of considerable geological and economic significance. In the southern and eastern part of the Arabian Plate, this unconformity has a differential erosion profile that facilitates a subcrop play with exploration potential. Identifying subtle stratigraphic traps is challenging, but by combining GDE facies with the mapped preservation limit for each sequence, it is possible to identify areas where rudist‐rich reservoir facies with potential karst enhancement are overlain by a regional claystone seal, high‐grading areas with subcrop trap potential.

A shared earth approach to siliciclastic reservoir characterization: The Zubair Fm of Northern Kuwait

An innovative, integrated characterization workflow is applied to complex siliciclastic reservoirs of the Lower Cretaceous Zubair Formation in the Bahrah Field of Northern Kuwait. A detailed sedimentological and petrophysical assessment, integrated with 3D seismic interpretation, constrained and delineated vertical and lateral facies changes within the field, which is also affected by complex fault and fracture patterns. Siliciclastic geo-bodies have been documented and mapped in 1D, 2D and 3D using seismic stratigraphy, seismic attributes and high-resolution seismic inversion reservoir characterization workflows. The spatial distribution of these geo-bodies appears to show the development of fluvio-deltaic systems in the southern and central sectors of the field, which evolved into marine dominated/tidally influenced deltaic systems towards the northern and eastern sectors. Two major fluvial channels trends have been identified: SW-NE and W-E, with a dominantly NE trending deltaic progradation. Towards the north, elongated (tidal mouth?) sand bars have been interpreted with a NW-SE trend. An integrated sequence stratigraphic framework was consequently developed to better assess the influence of relative sea level changes on sedimentary facies. This framework pointed to the influence of marine incursions and subsequent flooding surfaces, which lead to the development of shale-rich seals and/or baffles that could increase the probability of structural-stratigraphic trapping mechanisms in these depositional environments. This integrated workflow was utilized to update a numerical static reservoir model, which further de-risked future drilling locations and potentially charged reservoir volumes.

Rapid prediction of flood inundation by interpolation between flood library maps for real-time applications

It is important that real-time flood forecasting provides information on inundation extents and depths to emergency responders for flood mitigation planning, warning and rescue operations. Conventional hydrodynamic flood inundation modelling is generally not suited for real-time operations because of its large computational demand. The most widely adopted industry practice is to link a pre-canned library of flood maps with river levels and use an interpolation approach to derive flood surfaces and depths based on selected model inputs. However, there is surprisingly scant information in the literature on the procedures and performance of the library interpolation approach. In this study, we describe the library interpolation approach, introduce univariate and multivariate interpolation schemes, and investigate their performance through a case study of a river in Port Fairy, Australia. The MIKE 11/21 hydrodynamic model was used to construct a pre-canned flood inundation library of design events. The hydrodynamic model was also used to generate outputs for four test cases to evaluate the performance of the library interpolation approach. It is found that the accuracy of the library interpolation approach relies heavily on how the map library was constructed, selection of flood drivers, and shape and timing of hydrographs. The widely deployed univariate interpolation scheme based on a single primary flood driver yields results of varied accuracy, depending on the validity of assumptions, often made implicitly, about the inputs of the non-primary drivers. A newly developed multivariate interpolation scheme overcomes this problem. Overall, it is found that the results obtained using the map library interpolation schemes are generally satisfactory, achieving a hit rate of 0.85-0.99 and a critical success index of 0.85-0.99. However, a major limitation of the library interpolation approach is that the shape and timing of the input hydrographs need to be similar to that used in constructing the map library. Further research is needed to mitigate this limitation.

Resolving stratigraphic architecture and constraining ages of paralic strata in a low‐accommodation setting, Firebag Tributary, McMurray Formation, Canada

AbstractThe McMurray Formation in McMurray Depocentre, Canada, is typically subdivided into stratigraphic units based on regionally mappable marine mudstones, the bases of which define flooding surfaces (bottom to top: Lower McMurray, C2, C1, B2, B1, A2, A1 depositional unit). However, the McMurray Formation comprises a variety of palaeoenvironments, with the north‐eastern Firebag Tributary hosting significant delta‐plain deposits in the Lower McMurray and B1 depositional units. Facies analysis of 60 cores and 4763 wireline logs was used to resolve the palaeoshoreline trajectory and stratigraphic architecture in Firebag Tributary. Of 14 identified facies, three delta‐plain facies reveal: (1) eluviated palaeosols, interpreted as shrublands and woodlands formed during base‐level fall; (2) gleyed palaeosols, interpreted as tidal marshes; and (3) coals formed in coastal mires, the two latter facies are interpreted to accumulate during base‐level rise. Eluviated palaeosols occur below the Lower McMurray coal seam, implying valley incision and a maximum regressive surface. Gleyed palaeosols underlying the coal seam atop the B1 depositional unit do not record base‐level fall. Wetting‐upward coals overlying either palaeosol facies indicate base‐level rise (i.e. major flooding surface). B1 depositional unit coals and gleyed palaeosols are overlain by shallow‐marine facies or are eroded by wave ravinement during transgression. Consequently, the tops of coals or gleyed palaeosols correlate to the bases of regional marine mudstones elsewhere in McMurray Depocentre. Stratigraphic cross sections showcase palaeoshoreline regression and transgression. During the Lower McMurray and B1 depositional units, widespread coals and palaeosols indicate the palaeoshoreline resided near the western edge of Firebag Tributary. Regression during C2 through B2 depositional units and A2 and A1 depositional units resulted in palaeoshorelines near the Alberta–Saskatchewan border. To complement a previously dated Lower McMurray ash (121.39 ± 0.2 Ma), a new high‐confidence maximum depositional age from ash in the B1 coal seam (115.09 ± 0.16 Ma) allows an estimate to be made of depositional duration, indicating depositional units represent ca 0.16 Myr.

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.

Distinguishing the Miocene Kiel and Antwerpen Members (Berchem Formation) and their characteristic horizons using cone penetration tests in Antwerp (northern Belgium)

The glauconitic sands in the upper part of the lower‐middle Miocene Berchem Formation are subdivided into the Kiel and Antwerpen Members. Although lithological differences between both members are well known from temporary outcrops in the Antwerp city area, they are difficult to distinguish in boreholes, which hinders regional mapping of these units. In this study, we investigate whether both members can be distinguished on cone penetration tests (CPTs). For this purpose, we correlated multiple outcrops—in which the Kiel and/or Antwerpen Members have been identified—with nearby CPTs. On the CPTs, the boundary between the Kiel and Antwerpen Members is clearly identifiable as it coincides with an abrupt upwards decrease in cone resistance (qc). The lower qc of the basal part of the Antwerpen Member is probably related to the finer grain size with more clayey admixture compared to the underlying Kiel Member. This change to a finer grain size is caused by a decrease in depositional energy and sedimentation rates as the region was transgressed during the eustatic sea‐level rise at the start of the Mid‐Miocene Climatic Optimum. On the CPTs, several spikes in qc values were observed within the Antwerpen and Kiel Members. These spikes could be correlated to shell beds, three horizons with sandstones and possibly a hardground. The sandstones appear to be discontinuous, whereas some of the shell beds could be traced across the entire study area. Most shell beds probably represent storm deposits within an otherwise relatively low energetic sedimentary environment. A phosphatic shell bed above the base of the Antwerpen Member is interpreted as the maximum flooding surface, lying in a zone with the lowest qc values for the Antwerpen Member, which might reflect maximum fining. The shell beds and interlayered sands of the Antwerpen Member thin in a southern direction, indicating reduced accommodation space in this direction.

Electro-sequence analysis and natural resources potential of a transitional environment in central swamp depobelt, Niger delta, Nigeria

Sequence stratigraphy and Electrosequence of the Don-Field Central Swamp depobelt of the Niger Delta Basin, was carried out using well logs, biostratigraphic and core data. The aim of this study is to re-characterise and revalidate the reservoirs within the study area and provide an optimum framework for predicting reservoir character, development and reservoir quality distribution. Detailed petrophysical evaluation reveals proficient hydrocarbon reservoir units with variable parameters (i.e. porosity, permeability and shale volume) that can accommodate productive hydrocarbon reserve. Core data analyses revealed heavy minerals like pyrites and glauconites that can be of economic interest. The gamma wireline signatures of the wells show reservoir units that are predominantly blocky in shape indicative of fluvial channels. Fluvial channels are typically associated with coastal and/or marginal marine environments. More so, the aforementioned observations were validated using palaeoenvironmental interpretation of strata penetrated by Well-1, Well-2, and Well-3 via the sidewall core analyses. Sequence stratigraphic surfaces such as maximum flooding surfaces (MFS) and sequence boundary (SB) were observed to show good correlation with palynological and foraminiferal zones. The stacking patterns (i.e. progradation, retrogradation and aggradation) encountered gave acumen into systems tracts (i.e. lowstand system tract (LST), transgressıve system tract (TST) and highstand system tract (HST) interpretation. These system tracts constitute a depositional sequence set of middle—late Miocene age bounded chronologically by MFS of 9.5 Ma, 12.8 Ma, 15.0 Ma, 15.9 Ma and SB of 12.1 Ma, 13.1 Ma, 15.5 Ma, 15.9 Ma. The SB and MFS were delineated based on Shell Petroleum Development Company (SPDC) biozonation scheme: F-zone and P-zone were within P820-P680 and F9500-F9600/F9700 as contained in the biofacies interpreted data of index fossils (Globorotalia foshi S.I; Globorotalia praefohsi; Globorotalia peripheroacuta; Orbulina spp; Praeorbulina sicana; Paragloborotalia mayeri; Neogloboquadrina acostaensis) which corresponded to the alphanumeric code N8–N16 planktonic foraminiferal zones of Blow.

Facies and Sequence Stratigraphic Study of Bema Field, Niger Delta, Nigeria

Facies architecture and sequence stratigraphic framework of a potential hydrocarbon Prospective Area of Bema Field, Central Swamp Depobelt, Niger Delta was investigated. This study utilized Well Logs, Side Well Samples, Biostratigraphic Data and 3-D Seismic. The study revealed four facies unites, namely, Sandstone facies (SF), Shaly-Sandsone facies (SSF), Mudsone facies (MF), and Heterolithic facies (HF). The Sequence Stratigraphic analysis of the field revealed Nine (9) stratigraphic surfaces, comprising of (Five Maximum Flooding Surfaces (MFSs) with ages ranging from 20.7 to 15.0 Ma, and Four Sequence Boundaries (SBs) with ages between 20.4 and 15.5 Ma respectively). Five Vail’s third order depositional sequences (SQ1, SQ2, SQ3, SQ4, and SQ5) and four (4) Galloway’s genetic sequences (GQ1, GQ2, GQ3 and GQ4) were recognized within the study area based on Stratigraphic Marker tops and system tracts. Hydrocarbon play assessment revealed that the HST and TST are key reservoir rocks in the study while the shale of the TST therefore forms the seal for the potential traps in the study area.

Compositional, micromorphological and geotechnical characterization of Holocene Tiber floodplain deposits (Rome, Italy) and sequence stratigraphic implications

AbstractThis study reports a high‐resolution micromorphological characterization of floodplain deposits to investigate the relationships among compositional, textural and geotechnical data, and integrate soil micromorphology with sequence stratigraphy. Compositional and textural characterization of facies associations and soil features are calibrated against geotechnical parameters. The latter, obtained from cone penetration and pocket penetrometer tests from a borehole advanced 60 m into the Tiber channel belt and floodplain, show that depositional features and post‐depositional modifications are intrinsically associated with cone penetration test parameters: cone resistance; sleeve friction; and friction ratio. Petrographic and micromorphological features document pedogenetic modifications across stratigraphic markers evidenced by faunal and plant activity, accumulation of peat, and typified by precipitation of heavy metals, iron oxides and secondary carbonates. All of these features developed in correspondence with alluvial flooding surfaces that are correlated with non‐marine and marine flooding surfaces recognized in the transgressive and highstand coastal and lagoonal deposits of the Tiber Depositional Sequence. These observations may serve as a model to reconstruct the sequence‐stratigraphic evolution of ancient relict soils. Nevertheless, additional criteria (for example, their stratigraphic position and correlative surfaces) are necessary to adequately interpret the genesis of such low‐rank stratigraphic surfaces. This work demonstrates that a combination between sedimentological and stratigraphic observations and soil micromorphology can be critical to supplement field observations and determine the relative effect of pedogenic and depositional processes on the organization, composition and texture, and geotechnical properties of floodplain in urban areas.

The oxic Coniacian-Santonian interval in the Kopet-Dagh Basin (NE Iran): Carbon isotope and benthic-planktic foraminiferal assemblages at the time of the last Cretaceous OAE

A middle Coniacian-middle Santonian interval has been studied in the Kopet-Dagh Basin (NE Iran) to reconstruct the paleoenvironmental conditions in the eastern part of Tethyan realm at the time of the last Cretaceous Oceanic Anoxic Event (OAE3). This succession is composed of a chalky limestone unit, sandwiched by light gray calcareous mudstone and marlstone beds. The δ 13 C curve indicates several minor positive shifts up to 1‰ in the studied section that is correlative to other carbon isotope curves from the Tethys and Boreal realms. A prominent upward increase of P/B ratio in the studied section suggests a relative sea-level rise toward the Santonian. Lithology (low carbonate contents) and faunal contents (high %benthic and higher infaunal benthic foraminifera) reveal that the lower part of the studied section was deposited in a neritic environment influenced by continental-derived nutrients and mesotrophic to eutrophic conditions. Enhanced carbonate contents, higher diversity of benthic foraminifera and dominance of epifaunal taxa suggest more oligotrophic conditions and/or higher oxygen concentrations in the interval equivalent with a δ 13 C positive shift, caused by a transgression phase at this time. The overlying deposits are characterized by the maximum flooding surface and the highstand phase. The stratification of water column and more oxygen consumption in this interval resulted in higher abundance of infaunal benthic foraminifera and decline of carbonate production in a bathyal environment. • Coniacian/Santonian boundary interval was deposited under oxic conditions in the E Tethys. • No black shales or anoxia mark this inferred OAE3 interval. • Sea-level fluctuations control foraminiferal assemblages in this study. • The δ 13 C curve reveals the diagnostic features of global Co/Sa boundary record.

Dinoflagellate biostratigraphy of Eastern Indonesia stratigraphy: key of petroleum exploration success

Several major discoveries in the eastern part of Indonesia (e.g. Tangguh and Abadi) have increased more petroleum exploration interest in the area. These sizeable discoveries encountered gas in the Jurassic sandstone, which is a key reservoir target in the Northwest Shelf of Australia. The Mesozoic sandstone provenance is located in the Australian Continental Plate or also known as the Sahul Shelf. Thousands of wells were drilled in the Sahul Shelf and the stratigraphy in this area is well understood. The extension of the Mesozoic sandstone towards Indonesian territory, with much less well information, is one of the keys of success for petroleum exploration. Refinement of the stratigraphy of the eastern part of Indonesia is crucial to understand the extension.To refine the stratigraphy of Eastern Indonesia, especially for the Mesozoic interval, dinoflagellates play a significant role. Several types of this marine biota have been used by Australian stratigraphers as markers. In the case where stratigraphic tie to Northwest Shelf Australia discoveries, key wells or standard chronostratigraphy, dinoflagellate understanding is critical.Dinoflagellate markers are used to mark several subdivisions of Plover Sandstone. Norvick (2001) used W. indotata and D. caddaensis Maximum Flooding Surfaces to subdivide the reservoir target into upper, middle and lower Plover Formation. These surfaces are named after dinoflagellates. More markers were identified to mark the source rock and seal in the petroleum system. To have a detail correlation from Indonesia to the NW Shelf, understanding of dinoflagellates is crucial.

Using whole rock and in situ pyrite chemistry to evaluate authigenic and hydrothermal controls on trace element variability in a Zn mineralized Proterozoic subbasin

The mid-Proterozoic stratigraphy of the McArthur Basin (Australia) contains some of the most well-preserved sedimentary rocks of Precambrian age, which are also host to giant, clastic dominant (CD-type) massive sulfide Zn deposits. The most recently discovered CD-type deposit (the Teena deposit) is located in the Teena subbasin and hosted by the 1.64 Ga Barney Creek Formation. The Teena subbasin, therefore, provides the perfect natural laboratory for evaluating authigenic and hydrothermal controls on trace element (TE) variability, both of which contribute to paleoenvironmental reconstructions and ore deposit models. As the Teena deposit formed beneath the paleoseafloor, this also provides the opportunity to evaluate TE zonation around a fossilized subseafloor replacement hydrothermal system. In situ laser ablation inductively coupled mass spectrometry (LA-ICP-MS) has been used to define compositional end members in diagenetic and hydrothermal pyrite. The overgrowth of hydrothermal sulfides on diagenetic pyrite is associated with TE anomalism (Tl, Pb, As, Zn) that extends > 100 meters above the main high grade sulfide mineralization the Teena subbasin. The vertical zonation in TEs is consistent with the infiltration of hydrothermal fluids into overlying hangingwall sediments that were undergoing diagenesis. Bulk rock lithogeochemical data record covariation between total organic carbon (TOC) and a suite of TEs (Mo, Co, Ni, V). We suggest this was caused by local hydrographic factors during deposition of the Barney Creek Formation. High TOC/P molar ratios, resulting from regeneration of P in a euxinic water column, are associated with an interval overlying the main maximum flooding surface in the subbasin. The relationships between TOC, P and TEs resemble the redox architecture of a silled basin rather than an open marine margin. Sulfidic conditions developed during periods of high productivity, which were linked to nutrient supply that was enhanced by connectivity with surrounding water masses. The evidence of redox bistability, involving a delicate balance between ferruginous (anoxic, non-sulfidic) and euxinic (sulfidic) conditions, is consistent with recent models for other mid-Proterozoic sedimentary units. Nevertheless, there was a strong localised (101 km2) control on the authigenic and hydrothermal TE chemistry of the Barney Creek Formation in the Teena subbasin, which highlights a key challenge when extrapolating from data collected in partially restricted intracontinental marine settings.