Deep-water Basin Research Articles

Sensitivity analysis of seismic attributes and oil reservoir predictions based on jointing wells and seismic data – A case study in the Taoerhe Sag, China

It is important to identify the location of gravelly sandstone in Taoerhe Sag, an oil target area in the Chezhen Depression. To date, most attention has focused on sedimentary characteristics; hence, information regarding a clear sensitivity analysis of seismic attributes is incomplete. To address this, we used well analysis and seismic attribute interpretation to find sensitive seismic attributes and sand bodies. Based on the well analysis and core data, a geologicald model of mudstone and sandstone was established, and the electrical characteristics of three kinds of lithology were identified. We used correlation analysis to select the optimal logging parameters and seismic attributes to identify sandstone. We used multi-attribute fusion technology and stratigraphic slices to characterize the spatial distribution characteristics of gravelly sandstone in the target area and used genetic algorithm inversion volume to evaluate the prediction results. The results indicate that the three main lithologies of the lower submember of Shahejie Formation 3 (P2S3X) in the Taoerhe Sag can be distinguished by natural gamma (GR), acoustic time difference (AC) and saturated hydrocarbon content (SH) logging curves. The seismic attribute characteristics of gravelly sandstone of P2S3X are high root mean square amplitude (RMS) values, high instantaneous bandwidth (BW) values, low 3D curvature (Curv) values, medium-high instantaneous phase (Phase) values and high instantaneous frequency (Freq) values. In this study, we found two nearshore underwater fans in P2S3X. Gravelly sandstone is located along the slope zone and the lake bottom, with a total sedimentary area of 57.9 km2. The method summarized in this paper can be applied to other similar deep-water basins.

Sedimentological Analysis of the Turbidite Sequence in the Northern Part of the West Crocker Formation, Northwest Sabah

Gravity-flow deposits form the northern part of the Crocker Formation (Oligocene–Early Miocene), with the most significant interpretation as a sand-rich system in the proximal and a mud-rich system in the distal area of the deep-water turbidite depositional setting. Seven outcrop localities in the northern-part area were selected for mapping and sampling, starting from Kota Kinabalu up to the Telipok area to evaluate the sedimentary sequence. This study used mapping, field observation, and log sketches in the field, as well as extensive analysis and interpretation of sedimentological methods to investigate the sequence of sediment outcrops in the Crocker Formation area of northwest Sabah. During the fieldwork, five main facies were found, namely, massive sandstone facies (f1), graded sandstone facies (f2), laminated sandstone facies (f3), interbedded sandstone and mudstone facies (f4), and mudstone facies (f5). These northern-part outcrops are interpreted as being deposited from the highest to the lowest turbidity currents and the actuality of pelagic mudstone deposition, based on their fining-coarsening-upward pattern. The five geometrical bodies were proposed as laterally contiguous depositional environments, namely, (1) inner fan channel, (2) inner fan channel–levee complex, (3) mid-fan channelized lobes, (4) non-channelized lobes/distal lobes, and (5) basin plains. The facies interpretation shows that the study area consists of lobes, channel–levee complexes, and levees formed in a fan of a deep-water basin setting, with the basinal plain enveloped by thick mudstone deposits. This northern part of the Crocker Formation is interpreted as a multiple-sourced sediment, shelf-fed, Type II, low-efficiency, and sand-rich turbidite depositional system.

Structural and tectonic conditions for the development of the Bering Sea sedimentary basin

Introduction. In order to characterize the oil and gas potential of any area under exploration, its structural and tectonic evolution should be studied. In this paper, a structural and tectonic modelling of the Bering Sea is carried out.Aim. To identify the structural and tectonic characteristics of the Bering Sea by interpreting the results obtained during a geodynamic analysis of sedimentary basin formation, based on the tectonic and geodynamic paleoreconstructions and sedimentary basin modelling of the Bering Sea.Materials and methods. A structural and tectonic modelling of the Bering Sea sedimentary basins was carried out using contemporary methods of basin analysis and numerical geological modelling (PetroMod software, Schlumberger). Three-dimensional time-spatial structural-tectonic models of the Bering Sea were formed using the bottom structural maps of Pliocene-Quaternary deposits, near the Lower Miocene and Oligocene tops and along the acoustic basement bottom. Maps were digitalized and converted to grids (with a 500-m step), in which the discrepancies (intersections) were removed taking into account the available geological and geophysical data (seismogeological sections). The contemporary surface of sedimentary basins was constructed by the connection of bathymetric and topographic maps. The beginning and end time of sedimentary accumulation periods was determined in accordance with the international stratigraphic scale.Results. The performed study identified the sufficiently continuous development areas of the oceanic or suboceanic crust of deep-water (back-arc) basins, aged from the Upper Jurassic-Cretaceous to the Cenozoic and repeatedly affected by the subsequent phases of the tectonic and magmatic activation; development belts of the Cretaceous-Cenozoic block-magmatic basement of island arcs, locally including reformed basement blocks of an older, Paleozoic or Cimmerian, consolidation; extensive depth-differentiated alpine/newest (syn-oceanic) shelf platforms, occassionally partially destroyed due to the latest destruction, including blocks or large blocks of Pre-Cambrian or Paleozoic relatively rigid massifs in the structure of their base.Conclusion. The modelling results indicate the deeply submerged West Anadyr, East Anadyr and Central Anadyr basins to be possible depocentres with their own hydrocarbon generation centres.

Marketing research of the range of medicinal products based on salts of natural origin

As a source of supply of a balanced complex of salts in pharmaceutical practice, sea water (MW), sea salt (MS), obtained by the method of ordinary evaporation, or salt solutions made from standardized raw materials are used. Deep seawater (SW), typically pumped from depths greater than 200 m, contains a wealth of trace elements, including magnesium, calcium, potassium, chromium, selenium, zinc, and vanadium. Due to this, SW has the potential of a source and raw material for the creation of medicinal products for human health.
 The purpose of the work was to research the assortment of preparations based on salts of natural origin and analyze the segment of such products on the pharmaceutical market of Ukraine as of June 2022.
 The research was conducted on the basis of data from the State Register of Medicinal Products of Ukraine, the Morion information search program, and the classification system of the ATS electronic resource Compendium.online. Methods of structural, statistical and graphic analysis were applied in the work, and their generalization and systematization was carried out.
 It was established that on the pharmaceutical market of Ukraine, the segment of medicines, medical products and cosmetics, the source of active substances of which is SW and/or SS, is represented by 150 trade names. It was determined that by type of registration, the most common are medical products (51%) and cosmetics (42%), only 7% of registered drugs are registered. Manufacturers use sea water obtained from the deep water basins of the Adriatic, Aegean, Mediterranean Seas, Atlantic Ocean, Kankal Bay, sea water of Gullmarsfjorden. Domestically produced drugs of the investigated market segment occupy a share of 57%. Among the importing countries, the leaders are Croatia (9%) and Poland (5%). The analysis of the nomenclature established that the most common medicinal form of the drugs are nasal sprays (78%).
 The obtained data show that as the active substance of saline solutions, manufacturers declare SS (56% of the nomenclature) and SW (53%), however, not all products contain information about the source of origin of SS/SW. It was determined that there are no products on the pharmaceutical market of Ukraine based on the SW and SS of the Black and Azov seas, which is the basis for research and the creation of new drugs of domestic production.

Spatiotemporal evolution of late Neoproterozoic marine environments on the Yangtze Platform (South China): inking continental weathering and marine C-P cycles

Abstract The geodynamic reorganization of major cratonic blocks during the assembly of Gondwana in the late Neoproterozoic caused a (bio)geochemical evolution of marine habitats that witnessed fluctuating seawater oxygenation and nutrient fluxes. Previous studies of carbonates deposited on the Yangtze Platform (South China) have shown their use as reliable archives of paleo-redox and bio-productivity changes intrinsically linked to continental weathering fluxes and water mass cycling. Despite its complex submarine morphology, only a few carbonate-bearing sections comprising deeper depositional environments of the Yangtze Platform have been evaluated. Here we report temporal, lateral, and vertical variations of stable C and radiogenic Sr, Nd, and Os isotopic compositions together with trace element and rare earth and yttrium (REY) systematics in carbonates from the Doushantuo Formation representing different paleo-marine environments of the Yangtze Platform, including I) inner shelf, II) restricted intra-shelf basin, III) slope and IV) deep-water basin sections to trace the extent and evolution of paleo water masses. Variations in shale-normalized (subscript SN) Ce anomalies argue for variably oxidizing atmosphere/ocean conditions. The combination of REY SN systematics with carbonate associated P enrichments defines three distinct local water masses from which the carbonates precipitated: i) fully oxidized shallow-water, ii) nutrient-poor intra-shelf basin waters, and iii) organic carbon-rich slope and deep-waters with temporal evolution to higher dissolved p O 2 . Negative carbon isotope excursions in the carbonates such as during the putative Shuram equivalent Doushantuo Negative Carbon Excursion (DOUNCE) correlate with less negative Ce SN anomalies and ambient seawater shifts to more radiogenic initial 87 Sr/ 86 Sr and 187 Os/ 188 Os, but unradiogenic 143 Nd/ 144 Nd compositions, arguing for coupling of redox and weathering trends. Our comprehensive geochemical study highlights the vertical and temporal variations of physicochemical water mass properties recorded in late Neoproterozoic Yangtze Platform carbonates until the emergence of the first metazoans. Highlights • Intensive geochemical study spanning four paleo-depths on the Yangtze Platform • First carbonate Osmium isotopic compositions from the Late Neoproterozoic • Os, Nd and Sr isotope variations in concert with influx of terrigenous solutions towards the end of the Doushantuo Fm • REY systematics and P enrichments reveal significantly different water masses along the passive margin of the Yangtze craton • Changes in C-P cycles during Shuram anomaly linked to intensified terrigenous solution flux

Stratigraphy and depositional evolution of the terminal Ediacaran platform in the central to northern Sichuan Basin, Southwest China

The upper Ediacaran Dengying Formation in the Sichuan Basin provides well-preserved sedimentary records for investigating Precambrian microbialites and platform evolution. However, as previous studies have mainly focused on the broad platform-basin architecture, the depositional evolution of the platform has not been fully illuminated in the central to northern Sichuan Basin, where an intraplatform rift trough developed. Therefore, based on drilling wells and outcrops in the area, 20 lithofacies were identified and grouped into eight lithofacies associations indicating peritidal flat, shallow subtidal flat, lagoon, mixed tidal flat, slope, basin, coast and shallow sea environments. Moreover, two transgressive-regressive depositional cycles (Cycle 1 and Cycle 2) were recognized based on the five shallowing-upward (types A–E) and three deepening-upward (types F–H) cycle types. A ramp-like epeiric platform with a gentle slope developed in Cycle 1. The platform is dominated by shallow subtidal grainstones and peritidal microbialites, and the trough is in a slope environment without deep-water basin facies. In the transgression of Cycle 2, a siliciclastic-dominated environment comprising the coast and shallow sea developed on the shelf. Then a rimmed carbonate platform developed in the regression of Cycle 2, with the accumulation of shoal grainstone and peritidal microbialite in the platform margin, lagoonal dolomudstone in the platform interior, and steep slope rhythmite and basinal chert in the distal rift trough. Eustatic sea-level fluctuation and climatic change controlled the lithological transitions between carbonate and siliciclastic deposits. The platform configuration change is closely related to the evolution of the rift trough, which is the result of intense differential subsidence and sedimentation rates between the trough and platform under the effect of pre-existing basement rifts and coeval growth fault activities. A detailed depositional history of the Ediacaran Dengying Formation around the intraplatform rift trough was finally obtained, providing a good template for the study of the Precambrian microbialite-dominated platform with a similar tectonic setting.

Multifractal properties of oil and gas indices in the Songnan Low Uplift of the Qiongdongnan Basin deepwater area

Recently, a high-quality reservoir was discovered in the Songnan Low Uplift in the eastern deepwater area of the Qiongdongnan Basin, northern South China Sea. To establish whether this area has good exploration prospects, this paper uses the multifractal moment method to analyse 2689 data points acquired from the basin in the SE of the southern low bulge. It is pointed out that the fractal behaviours of different types of geochemical indices are often distinguished by multifractal spectra of different shapes, therefore multifractal spectrum function analysis is used in this paper. These data were considered within the context of 13 oil and gas indices describing the multifractal spectrum function morphological characteristics. The results show that these indices can be divided into three types according to the multifractal spectrum. Indices with a strong multifractal spectrum function in the Songnan Low Uplift have the characteristics of a wide and continuous multifractal spectrum function, forming a right-skewed arc shape, while the other indices show weak or single-fractal characteristics. The results are in good agreement with principal component analysis results, where the spectral function of each principal component shows that the gas source of the C1, C2, C3, nC4, nC5, and heavy hydrocarbon indices in the Songnan Low Bulge has multifractal characteristics. The weight of these indices with strong multifractal characteristics shows that the principal components C1, C2 and C3, and heavy hydrocarbons, are important indices for delineating hydrocarbon prospects in the Songnan Low Uplift. Multifractal and spatial analysis techniques provide new ideas for index selection and comprehensive information extraction for oil and gas exploration. Thematic collection: This article is part of the Applications of Innovations in Geochemical Data Analysis collection available at: https://www.lyellcollection.org/cc/applications-of-innovations-in-geochemical-data-analysis

Geoscience Poster G16: Potential field interpretation and modelling in the deep-water Otway Basin

Poster G16 The NW–SE trending Otway Basin is a well-established hydrocarbon province with onshore and shallow-water offshore discoveries. However, the deep-water offshore is underexplored due to the sparsity of data in the past. New 2D seismic, gravity and magnetic data, acquired during the 2020 Otway Basin Seismic Program, were combined with legacy seismic data to improve the understanding of this part of the basin. The new data have been processed and integrated with existing open-file data to derive Moho and lithosphere–asthenosphere boundary surfaces. Additional wavelength filtering of the newly acquired magnetic and gravity data, using constraints from seismic data, provides valuable information on the geometry and the spatial extent of igneous rocks in the deep-water basin. While extrusive igneous rocks and related intrusive rocks in the Otway Basin can be inferred from seismic reflection data, the new magnetic and gravity data provide additional constraints that help to map their distribution across the basin. To access the poster click the link on the right. To read the full paper click here

Contrasting responses of phytoplankton productivity between coastal and offshore surface waters in the Taiwan Strait and the South China Sea to short-term seawater acidification

Abstract. Seawater acidification (SA) has been documented to either inhibit, enhance, or result in no effect on marine primary productivity (PP). In order to examine the effects of SA in changing environments, we investigated the influences of SA (a decrease of 0.4 pHtotal units with corresponding CO2 concentrations in the range of 22.0–39.7 µM) on PP through deck-incubation experiments at 101 stations in the Taiwan Strait and the South China Sea, including the continental shelf and slope, as well as the deep-water basin. The daily primary productivities in surface seawater under incident solar radiation ranged from 17–306 µg C (µg Chl a)−1 d−1, with the responses of PP to SA being region-dependent and the SA-induced changes varying from −88 % (inhibition) to 57 % (enhancement). The SA treatment stimulated PP in surface waters of coastal, estuarine, and shelf waters but suppressed it in the South China Sea basin. Such SA-induced changes in PP were significantly related to in situ pH and solar radiation in surface seawater but negatively related to salinity changes. Our results indicate that phytoplankton cells are more vulnerable to a pH drop in oligotrophic waters. Contrasting responses of phytoplankton productivity in different areas suggest that SA impacts on marine primary productivity are region-dependent and regulated by local environments.

Assessing the sealing quality of submarine mass transport complexes and deposits

Mass transport complexes and their associated mass transport deposits—both referred to here as submarine failure deposits—are virtually ubiquitous in the modern and ancient sedimentary record of many deepwater basins. As exploration expands to new frontiers, submarine failure deposits are being identified as components of the petroleum system in numerous prospects. Although such deposits were historically considered facies to avoid from a viewpoint of petroleum exploration, it is now recognized that they can act as source, reservoir, or seal elements. In this paper, we set out to investigate the role of submarine failure deposits as effective seals in the petroleum system using published data and propose a methodology to risk some first-order factors at a macro-, meso-, and micro-scale that influence the seal quality of these submarine failure deposits. We accomplish this by discussing the properties intrinsic to submarine failure deposits that affect the seal quality at different scales. Based on published literature, at least six offshore fields from the Gulf of Mexico and NW Borneo are reported to have a submarine failure deposit as an effective seal. These fields combined account for ∼0.9 billion barrels of oil equivalent of cumulative discovered reserves globally and prove the potential of submarine failure deposits as effective seals and a future undervalued play concept. We use three case studies to illustrate our methodology. Our methodology can be further customized using datasets from industry and public records. The seal risk matrix presented here is based on more than a decade of research and has been already used by several exploration companies with encouraging feedback. We acknowledge the limitations of the methodology, but future interdisciplinary research and integration of new datasets and results will improve the de-risking of submarine failure deposits in exploration. Additionally, this methodology can potentially be applied to assessing seal potential of submarine failure deposits for carbon capture sequestration and storage projects.

Potential field interpretation and modelling in the deep-water Otway Basin

The NW–SE trending Otway Basin is a well-established hydrocarbon province with onshore and shallow-water offshore discoveries. However, the deep-water offshore is underexplored due to the sparsity of data in the past. New 2D seismic, gravity and magnetic data, acquired during the 2020 Otway Basin Seismic Program, were combined with legacy seismic data to improve the understanding of this part of the basin. The new data have been processed and integrated with existing open-file data to derive Moho and lithosphere–asthenosphere boundary surfaces. Additional wavelength filtering of the newly acquired magnetic and gravity data, using constraints from seismic data, provides valuable information on the geometry and the spatial extent of igneous rocks in the deep-water basin. While extrusive igneous rocks and related intrusive rocks in the Otway Basin can be inferred from seismic reflection data, the new magnetic and gravity data provide additional constraints that help to map their distribution across the basin.

Long-term dynamics of forage base and food supply for nekton in the upper epipelagic layer of the western Bering Sea. Part 2. Food supply for nekton

Interannual dynamics of feeding conditions for nekton in the upper epipelagic layer of the western Bering Sea is considered for the summer and fall seasons of 2002–2020. In the summers, daily consumption by fish and squids ranged from 0.01 to 0.10 t/km2 in the deepwater basins and between 0.01–0.38 t/km2 in the shelf area at Cape Navarin. In the falls, the consumption increased to 0.03–0.14 t/km2 in the deep-water basins, and to 0.01–0.53 t/km2 in the Navarin area. Summary in the summer-fall periods, the fish and squids consumed 2–5 % of zooplankton production (up to 5–7 % in some years) in the deep-sea basins that is rather low degree of the zooplankton resources usage. In the Navarin area, the consumption is considerably higher and is estimated as 5 % in summer and 21 % in fall season, on average. In cases of heightened nekton biomass and reduced zooplankton biomass in some years, the grazing pressure on plankton increased, in particular on euphausiids, hyperiids and pteropods, while the intensity of salmon feeding decreased, with extension the portions of nektonic food and other zooplankton groups, as arrowworms, in their diet. On the other hand, the portion of juvenile fish and squids in the salmon diet increased in cases of high abundance of this prey, too. Weak correlation was detected both between the salmon feeding and abundance of their prey and between the salmon feeding and abundance of salmons. The feeding conditions for pink salmon during their offshore migration did not determine the rate of their returns. Strong year-classes of pink salmon had large returns in conditions of either poor or rich food supply in fall season, so the feeding in fall was not important for the pink salmon survival in the ocean in winter. Feeding of other fish and squids species did not change noticeably in the years with reduced food supply. In general, abundance and species composition of plankton and nekton communities were rather stable in the western Bering Sea in the 2000-2010s, and this current state of the ecosystem provides stable functioning of nekton communities both in the deepwater and Navarin areas.

QUATERNARY-RECENT OSTRACODS (PODOCOPIDA, PLATYCOPIDA) OF THE TYRRHENIAN SEA (ITALY)

The article provides the systematic description of eight species of ostracods described by Dykan (2018, 2020), belonging to the genera Bythocypris, Pontocypris, Pterygocythereis, Bosquetina, Acantocythereis and Cytherella, as well as eleven species in open nomenclature (sp., cf., ex gr.) of the genera Argilloecia, Loxoconcha, Sarsicytheridea, Pontocytheroma, Echinocythereis, Paleoblitacythereis, Pseudobosquetina and Bythoceratina. The ostracods derive from Upper Quaternary, Holocene and modern deposits of the southwestern part of the Tyrrhenian Sea. Sampling stations cover shelf, continental slope and deep water basin in 65-3500 m water depth. The systematic section provides synonymy, detailed descriptions, ecology, geographical and stratigraphical distribution of species. SEM-images of external and internal structures of the carapace like hinge, normal pore canals, macro- and mesosculpture are provided. The documented species belong to North Atlantic, West Atlantic, South Antarctic and Mediterranean zoogeographic groups according to the zoogeographical classification developed for the ostracods of the Tyrrhenian Sea.

The primary dolostone in the Meso-Neoproterozoic: Cases study on platforms in China

Meso-Neoproterozoic dolostone is abnormally well-developed in the platform areas in China, detailly, in the Mesoproterozoic Calymmian Wumishan Formation of North China Basin, Neoproterozoic Ediacaran Qigbulak Formation of Tarim Basin, and the Neoproterozoic Ediacaran Dengying Formation of Sichuan Basin. The outcrops and drilling cores from these basins show that these dolostones are mostly thick-bedded to massive, with mud-sized to silt-sized crystalline dolostone reaching 86%–97% of the total dolostone thickness. These dolostones basically suffered no secondary metasomatism, regardless of containing microorganisms (such as algae and bacteria) or not. The analyses of sedimentary palaeogeographic features indicate that: (1) the Meso-Neoproterozoic dolostone nearly covered the entire area basins, and was widely deposited in supratidal to intertidal zones, as well as in open platform environments; (2) the dolostone was subdivided according to the crystalline size, with the distribution controlled by geomorphology, i.e., the pure mud-sized crystalline dolostone developing in depression areas, whereas the grainy mud-sized crystalline dolostone or the mound stromatolitic mud-sized crystalline dolostone developing in uplift areas; (3) deep-water basins developed between the carbonate platforms, and the seismic profiles show that these basins were formed by syngenetic deep faults in the Meso-Neoproterozoic strata. These syngenetic faults increased Mg2+ concentration in the seawater by injecting rich-Mg2+-bearing hydrothermal fluids into the carbonate platforms. The analyses of geochemical and paleoclimatic indexes reveal that there is no obvious difference in carbon and oxygen isotope ratios between dolostones having different textures, with the ratios similar to those of the global seawater of the Meso-Neoproterozoic, indicating that the silt-sized crystalline dolostone has the same sedimentary origin as the mud-sized crystalline dolostone, i.e., the former is from authigenic recrystallization of the latter rather than secondary metasomatism. Therefore, whatever the crystalline sizes are, the dolostones are all originated from sedimentation. All the petrological, sedimentary and geochemical data suggest that the dolostones covering almost the whole Meso-Neoproterozoic typical platform areas of China are of relatively primary sedimentary origin.

Biostratigraphic evidence for incremental tectonic development of early Cambrian deep-water environments in the Misty Creek embayment (Selwyn basin, Northwest Territories, Canada)

The early evolution of the Misty Creek embayment (MCE), a prominent, northwest-trending sub-basin of the economically important Selwyn basin, is poorly understood. The abrupt contact between Cambrian Stage 4 (traditional lower Cambrian) carbonate ramp strata of the Sekwi Formation and overlying Miaolingian (traditional middle Cambrian) deep-water, calciturbiditic strata of the Hess River Formation has been regarded as diachronous. This important transition, which marks the onset of long-lived, deep-water conditions in the MCE, remains unexplained. This study uses biostratigraphic data from a previously undescribed location in the MCE, existing biostratigraphic and lithostratigraphic data from the 1970s, and regional thickness patterns to characterise the sharp yet diachronous transition from lithofacies typical of the Sekwi Formation to those typical of the Hess River Formation. The dramatic change in depositional environments was diachronous yet non-gradational, precluding a eustatic cause. The change was geologically abrupt, probably through two extension-related subsidence events, with different geographic extents, which heralded the MCE’s long life as a deep-water basin. The onset of deep-water conditions in the MCE occurred semi-contemporaneously with other extension-related events that are recorded in the northern Canadian Cordillera, demonstrating that Cambrian Series 2 – Miaolingian was a time of widespread extension and subsidence along the western margin of Laurentia.

Overview of the MOSAiC expedition: Physical oceanography

Arctic Ocean properties and processes are highly relevant to the regional and global coupled climate system, yet still scarcely observed, especially in winter. Team OCEAN conducted a full year of physical oceanography observations as part of the Multidisciplinary drifting Observatory for the Study of the Arctic Climate (MOSAiC), a drift with the Arctic sea ice from October 2019 to September 2020. An international team designed and implemented the program to characterize the Arctic Ocean system in unprecedented detail, from the seafloor to the air-sea ice-ocean interface, from sub-mesoscales to pan-Arctic. The oceanographic measurements were coordinated with the other teams to explore the ocean physics and linkages to the climate and ecosystem. This paper introduces the major components of the physical oceanography program and complements the other team overviews of the MOSAiC observational program. Team OCEAN’s sampling strategy was designed around hydrographic ship-, ice- and autonomous platform-based measurements to improve the understanding of regional circulation and mixing processes. Measurements were carried out both routinely, with a regular schedule, and in response to storms or opening leads. Here we present along-drift time series of hydrographic properties, allowing insights into the seasonal and regional evolution of the water column from winter in the Laptev Sea to early summer in Fram Strait: freshening of the surface, deepening of the mixed layer, increase in temperature and salinity of the Atlantic Water. We also highlight the presence of Canada Basin deep water intrusions and a surface meltwater layer in leads. MOSAiC most likely was the most comprehensive program ever conducted over the ice-covered Arctic Ocean. While data analysis and interpretation are ongoing, the acquired datasets will support a wide range of physical oceanography and multi-disciplinary research. They will provide a significant foundation for assessing and advancing modeling capabilities in the Arctic Ocean.

Neoproterozoic extensional basins and its control on the distribution of hydrocarbon source rocks in the Yangtze Craton, South China

• Neoproterozoic source rocks in the Yangtze Craton. • Structural and sedimentary patterns of the extensional basins evaluated. • The source rocks are related to the extensional basins, climate and life evolution. • Favorable areas for the source rock distribution are predicted. Hydrocarbon exploration in the Neoproterozoic extensional basins in the Yangtze Craton of South China has made prominent progresses in the past decades. However, the spatial distribution of source rocks across the craton still remains unclear. Here, we use outcrop observations, borehole data, and reflective seismic profiles to investigate the prototype, distribution and sediment infilling of these basins in the Yangtze Craton during the periods of source rock deposition. The basin prototype is categorized based on its tectonic origin and structural-sedimentary feature as follows. (1) During the deposition of the Datangpo Formation, rift basins extensively developed, band are characterized by a series of graben or half graben structures that consist of basin-controlling normal faults. The source rocks in the Datangpo Formation were deposited as the inner shelf basin or deep shelf facies, obtaining high thickness (i.e., 200 m) in the Wuling rift basin. (2) During the deposition of the Doushantuo Formation, the intracratonic rift basin and passive continental margin basin formed. These basins were controlled by syn-depositional faults that inherited the existing rift fault structures. The source rocks of the Doushantuo Formation were deposited as shelf lagoon, slope to deep-water basin facies. (3) During the deposition of the Dengying Formation, the intraplatform rift basin and passive continental margin basin developed with influence of regional tectonic extension. Not only are these basins affected by the preexisting faults, but also by the newly developed syn-depositional faults. The argillaceous source rocks of the Dengying Formation deposited as slope and deep-water basin facies. Further in-depth analyses revealed that a range of mechanisms may have contributed to the formation and distribution of source rocks in the Yangtze Craton, such as the break-up of the Rodinia Supercontinent, paleaolatitudes, glacial-interglacial geological events, basin extension and sedimentary environments. By integrating the distribution of the source rocks and the late tectonic reworking, this study predicts several targets for the source rock distribution in the Yangtze Craton, including in the central Sichuan, northeastern Sichuan, southern Shanxi, western Hubei, northeastern Guizhou-western Hunan, and the northeastern Guangxi-central Hunan areas.

Authigenic Minerals of the Derbent and South Caspian Basins (Caspian Sea): Features of Forms, Distribution and Genesis under Conditions of Hydrogen Sulfide Contamination

This paper presents the results of complex lithological, mineralogical, and geochemical studies of bottom sediments of deep-water basins of the Caspian Sea (Derbent and South Caspian Basins) in areas contaminated by hydrogen sulfide. In the course of complex studies, numerous manifestations of authigenic mineral formation associated with the stage of early diagenesis have been established. Authigenic minerals belonging to the groups of sulfates (gypsum, barite), chlorides (halite), carbonates (calcite, low Mg-calcite; kutnohorite), and sulfides (framboidal pyrite), as well as their forms and composition, have been identified by a complex of analytical methods (X-ray diffractometry (XRD), scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS); atomic absorption spectroscopy (AAS); coulometric titration (CT)); the nature of their distribution in bottom sediments has been assessed. Carbonates and sulfates are predominant authigenic minerals in the deep-water basins of the Caspian Sea. As a part of the study, differences have been established in the composition and distribution of associations of authigenic minerals in the bottom sediments in the deep-water basins. These are mineral associations characteristic of the uppermost part of the sediments (interval 0–3 cm) and underlying sediments. In the Derbent Basin, in sediments of the interval 3–46 cm, an authigenic association is formed from gypsum, calcite, magnesian calcite, siderite, and framboidal pyrite. An association of such authigenic minerals as gypsum and calcite is formed in sediments of the 0–3 cm interval. In the South Caspian Basin, in sediments of the interval 3–35 cm, an association of such authigenic minerals as gypsum, halite, calcite, magnesian calcite, and framboidal pyrite is formed. The association of such authigenic minerals as gypsum, halite, calcite, magnesian calcite, kutnohorite, and framboidal pyrite is characteristic of sediments of the 0–3 cm interval. We consider the aridity of the climate in the South Caspian region to be the main factor that determines the appearance of such differences in the uppermost layer of sediments of the basins. Judging by the change in the composition of authigenic associations, the aridity of the South Caspian increased sharply by the time of the accumulation of the upper layer of sediments (interval 0–3 cm). Taking into account lithological, mineralogical and geochemical data, the features of the processes of authigenic mineral formation in the deep-water basins of the Caspian Sea under conditions of hydrogen sulfide contamination have been determined. Analysis of the results obtained and published data on the conditions of sedimentation in the Caspian Sea showed that hydrogen sulfide contamination recorded in the bottom layer of the water column of the deep-water basins of the Caspian Sea may affect the formation of authigenic sulfides (framboidal pyrite), sulfates (gypsum), and carbonates (calcite and kutnohorite) associated with the activity of sulfate-reducing bacteria in reducing conditions.

Physical model test validation of dynamic similarity truncation method for an internal turret mooring system

The mooring system needs to be truncated in physical model test to adapt to the limited dimensions of offshore basins. Especially, the drag force and inertial force are required to be included in the dynamic mooring truncation methods, and the method should be verified by model test comparison. Here an effective dynamic truncation method is proposed based on slender rod theory and multi-objective cuckoo search optimization algorithm. The line tensions in time domain are transferred into frequency domain to implement the dynamic similarity. The proposed process can promote optimization efficiency in a great extent. In order to demonstrate the accuracy of the proposed method, a horizontal truncation is carried out to an internal turret moored FPSO working in 420 m water depth. The model test in deep-water basin is performed with static tests and irregular wave tests. It can be found that model test and numerical results show consistence on the static stiffness characteristics and dynamic response. The comparison verifies the reliability and accuracy of the proposed truncation method well.

Early Pennsylvanian sediment routing to the Ouachita Basin (southeastern United States) and barriers to transcontinental sediment transport sourced from the Appalachian orogen based on detrital zircon U-Pb and Hf analysis

Abstract Carboniferous sediment dispersal from the Appalachian orogenic system (eastern United States) has become a topic of widespread interest. However, the actual pathways for continental-scale, east-to-west sediment transfer have not been documented. This study presents detrital zircon (DZ) U-Pb ages and Hf isotopic values from the Lower Pennsylvanian (Morrowan) Jackfork Group and Johns Valley Shale of the synorogenic Ouachita deepwater basin of Arkansas to document provenance and delineate the likely sediment-routing systems within the broader context of sediment dispersal across Laurentia. Twelve (12) DZ U-Pb age distributions are interpreted to indicate that sediments were derived from the Appalachians to the east and northeast, as well as the midcontinent region to the north. All samples display prominent ca. 500–400 Ma, 1250–950 Ma, 1550–1300 Ma, and 1800–1600 Ma grains, consistent with ultimate derivation from the Appalachian, Grenville, Midcontinent, and Yavapai-Mazatzal provinces. DZ Hf values obtained from the Ouachita Basin are similar to published Hf values from Pennsylvanian samples in the Appalachian and Illinois Basins. Age distributions are generally consistent for seven samples collected from the Jackfork Group and Johns Valley Shale in the southern Ouachita Mountains through ~2400 m of stratigraphic section and are interpreted to indicate little change in provenance during the Morrowan in this part of the system. However, samples from the most northern and most source-proximal site in Little Rock, Arkansas, exhibit modest percentages of Appalachian ages and elevated contributions of Yavapai-Mazatzal ages when compared with samples collected farther to the south and west. We interpret differences between DZ signatures to indicate distinct sediment-routing pathways to the Ouachita Basin. We infer the strong Appalachian and Grenville signals to represent an axial system flowing through the Appalachian foredeep, whereas the more diverse signals represent a confluence of rivers from the northeast through the backbulge of southern Illinois and western Kentucky and from the north across the Arkoma shelf. Collectively, the Ouachita Basin represents a terminal sink for sediments derived from much of the eastern and central United States.