Search

The small forward-curved blades known as Sirocco fan units are very common and widespread solution for air conditioning used in public transportation applications, as buses or trains. The users quietness and comfort have become a main concerns in the automotive industry. For such kind of turbomachinery flow, the patterns becomes always highly 3D and unsteady, compromising the referred comfort, and setting the focus on the working flow variables. A mathematically exact solution for that flow, which would provide any required information on pressure or forces, is out of scope at the current engineering design processes. Nevertheless, some flow features and mechanical data are needed to progress in the frame of a modern industrial environment, involving maintenance protocols with important temporal and economic constraints for different design procedures. The correctness of a given maintenance protocol relies on its feasibility to handle a set of machine working parameters or variables, including a number of them as wide as possible. Doing so, a set of not-dangerous ranges for them can be established. Such ranges are often defined promoting a series of failures similar to real ones, when the machine is in its operative lifetime. In this paper and in order to establish proper working ranges for maintenance purposes, a series of failures have been experimentally tested for a Sirocco fan unit. Initially, real data from industry have been required and a list of main failures was made, including (1) impeller or rotor unbalance, (2) impeller channel obstruction and (3) blocked inlet. The failures are studied using a purified orbit diagram (POD) technique and a symmetrized dot pattern (SDP) technique. All four working conditions are studied for at least three different flow rates and, therefore, a deeper insight into the fan working parameters and options are made feasible. In the frame of the maintenance protocol, a full set of ranges for the considered failures has been obtained. Therefore, the present paper shows a novel possibility to enhance existing maintenance protocol using two advanced frequency-based techniques. [ABSTRACT FROM AUTHOR]

A comprehensive dataset is collated in a study on sediment transport, timing and basin physiography during the Early Cretaceous Period in the Boreal Basin (Barents Sea), one of the world's largest and longest active epicontinental basins. Long-wavelength tectonic tilt related to the Early Cretaceous High Arctic Large Igneous Province (HALIP) set up a fluvial system that developed from a sediment source area in the NW, which flowed SE across the Svalbard archipelago, terminating in a low-accommodation shallow sea within the Bjarmeland Platform area of the present-day Barents Sea. The basin deepened to the SE with a ramp-like basin floor with gentle dip. Seismic data show sedimentary lobes with internal clinoform geometry that advanced from the NW. These lobes interfingered with, and were overlain by, another younger depositional system with similar lobes sourced from the NE. The integrated data allow mapping of architectural patterns that provide information on basin physiography and control factors on source-to-sink transport and depositional patterns within the giant epicontinental basin. The results highlight how low-gradient, low-accommodation sediment transport and deposition has taken place along proximal to distal profiles for several hundred kilometres, in response to subtle changes in base level and by intra-basinal highs and troughs. Long-distance correlation along depositional dip is therefore possible, but should be treated with caution to avoid misidentification of timelines for diachronous surfaces. [ABSTRACT FROM AUTHOR]

Six submarine canyons are distributed along the active margin off SW Taiwan. Using multi-beam bathymetric data and reflection seismic profiles to determine canyon head locations with respect to shelf edge, five of these canyons were classified into the following three types: 1. river-connected; 2. shelf-indenting; and 3. slope-confined. The remaining canyon was re-interpreted as a sea valley. Type 1 canyon, the Kaoping Canyon, is directly connected to the Kaoping River and supplied with terrestrial sediment. The canyon head segment tends to generate hyperpycnal flows during flooding, causing intense erosion of seafloor across the shelf and slope and forming a major sediment conduit. The Penghu, Kaohsiung and Fangliao canyons are of type 2 and incise into the shelf, forming a V-shaped head segment with abundant slumping features. Without continuous sediment supply from rivers, the canyon head receives sediments mainly from local slope failures on canyon walls and is unable to generate intense erosive sediment flows, resulting in an indentation into the shelf over a short distance. Oceanographic/hydrodynamic measurements close to the canyons are still not available for the region, despite they could shed light on the on-going sediment dynamics in the area. The Shoushan Canyon is a type 3 canyon characterized by limited sediment input from the Kaoping Shelf and weak canyon erosion, especially during sea-level highstands, resulting in a relatively straight canyon course confined to the upper slope. These submarine canyons share common regional tectonics, sea-level changes and climatic conditions. However, they evolved via local processes mainly controlled by sediment input directly related to head location, resulting in distinct morphologies and sizes. These canyons have remained active during the present-day sea-level highstand. Frequent earthquake and flooding events are the major triggering factors for sediment failures and generation of subsequent turbidity currents, resulting in substantial incision into the canyon. The results of the present study indicate that the SW Taiwan margin is characterized by canyons of type 1 and type 2 (n = 4) with only one type 3 canyon. This represents large percentages of type 1 and type 2 canyons compared to other regions of the world. Narrow shelf and abundant sediment supply are the two main controls for the presence of river-connecting and shelf-incising canyons on the active Taiwan margin. [ABSTRACT FROM AUTHOR]

The Lishui Sag is on the southwest margin of the East China Sea Shelf Basin (ECSSB), which is located on the continental shelf of the East China Sea. The analysis of sedimentological signatures is based on 217 m (712 ft) of Paleocene cores showing a wide variety of lithofacies, sedimentary structures, ichnological data, seismic data, and log data. Eight lithofacies, nine typical ichnofabrics, and four ichnofacies combined with petrological, geophysical, and bioturbation information were identified as the key sedimentary facies characteristics for identifying three sedimentary systems in the study area. Eleven sedimentological facies are present in the three sedimentary systems: foreshore, upper shoreface, lower to middle shoreface, offshore transition, proximal fan delta front, distal fan delta front, wave-dominated delta front sand bar, wave-dominated delta front sand sheet, interbar, tide-influenced distributary channel, and tide-influenced interdistributary bay facies. The three sedimentary systems that were identified are fan delta, wave-influenced delta, and tide facies. Fan delta deposits are present in the southwest and northeast of the sag, with subaqueous fan delta front deposits dominating, whereas farther seaward successions are characterized by distal fan delta front deposits that are intensely bioturbated. Wave-dominated deltaic deposits occur mostly in the western and middle parts, where fluvial discharge in the delta front and prodelta have been repeatedly reworked by waves and formed some isolated bars distributed perpendicular to the source; these deposits are sparsely to intensely bioturbated. Tide facies develop locally and have been identified as distributary channels and interdistributary bay facies. [ABSTRACT FROM AUTHOR]

Integrated geological and geophysical investigations were successfully performed for reservoir modeling in an oil field in the Jambi Province sub-basin, Sumatra, Indonesia. The objective of this study is to characterize the oil reservoir in terms of its petrophysical properties using a facies model that is based on an integrated geological and geophysical approach. The reservoir target of this study is located in the Air Benakat Formation, which is identified with a thickness of 3 to 20 m and is deposited in a depth range of 1300–1500 m. The reservoir modeling of Air Benakat Formation is carried out to open a new discovery for this field, since the comprehensive reservoir modeling has not been intensively performed. Structurally, the reservoir is segmented into three compartments by four main faults, and stratigraphic investigations revealed three prospect layers. In the present framework of the depositional environment, assessments of well log data included formation evaluations, well log data correlations and sequence stratigraphy, were performed to produce high-resolution features of vertical and lateral distributions. In addition, seismic data were interpreted to guide the structural model, and to effectively construct a three-dimensional (3D) geological framework of reservoir properties. The modeled reservoir shows that the reservoir is primarily considered a transition zone to a shallow marine deposit, which is specifically located in a submarine fan channel with a plain/moderately steep angle of its sedimentation base. Depositional environments are generally characterized by the potential paleocurrent direction within the channel axis from NE to SW, with respective agreement from larger scale porosity and net/gross models. [ABSTRACT FROM AUTHOR]

The monitoring of turbidity currents enables accurate internal structure and timing of these flows to be understood. Without monitoring, triggers of turbidity currents often remain hypothetical and are inferred from sedimentary structures of deposits and their age. In this study, the bottom currents within 20 m of the seabed in one of the Pointe‐des‐Monts (Gulf of St. Lawrence, eastern Canada) submarine canyons were monitored for two consecutive years using Acoustic Doppler Current Profilers. In addition, multibeam bathymetric surveys were carried out during deployment of the Acoustic Doppler Current Profilers and recovery operations. These new surveys, along with previous multibeam surveys carried out over the last decade, revealed that crescentic bedforms have migrated upslope by about 20 to 40 m since 2007, despite the limited supply of sediment on the shelf or river inflow in the region. During the winter of 2017, two turbidity currents with velocities reaching 0·5 m sec−1 and 2·0 m sec−1, respectively, were recorded and were responsible for the rapid (<1 min) upstream migration of crescentic bedforms measured between the autumn surveys of 2016 and 2017. The 200 kg (in water) mooring was also displaced 10 m down‐canyon, up the stoss side of a bedform, suggesting that a dense basal layer could be driving the flow during the first minute of the event. Two other weaker turbidity currents with speeds <0·5 m sec−1 occurred, but did not lead to any significant change on the seabed. These four turbidity currents coincided with strong and sustained wind speed >60 km h−1 and higher than normal wave heights. Repeat seabed mapping suggests that the turbidity currents cannot be attributed to a canyon‐wall slope failure. Rather, sustained windstorms triggered turbidity currents either by remobilizing limited volumes of sediment on the shelf or by resuspending sediment in the canyon head. Turbidity currents can thus be triggered when the sediment volume available is limited, likely by eroding and incorporating canyon thalweg sediment in the flow, thereby igniting the flow. This process appears to be particularly important for the generation of turbidity currents capable of eroding the lee side of upslope migrating bedforms in sediment‐starved environments and might have wider implications for the activity of submarine canyons worldwide. In addition, this study suggests that a large external trigger (in this case storms) is required to initiate turbidity currents in sediment‐starved environments, which contrasts with supply‐dominated environments where turbidity currents are sometimes recorded without a clear triggering mechanism. [ABSTRACT FROM AUTHOR]

The circum-Nile deformation belt (CNDB) demonstrates the interaction between a giant delta and a giant salt body. The semi-radial shape of the CNDB is commonly interpreted as the product of salt squeezing out from under the Nile Delta. We demonstrate, however, that this is not the dominant process, because the delta and its deep-sea fan do not reach the deep-basin salt. The distal part of the deep-sea fan overlies the edge of the salt giant, but squeezing this edge (<150 m thickness) should have had only little effect on the regional salt tectonics. Only on the easternmost side of the deep-sea fan, toward the Levant Basin, does the squeeze-out model work. Here, the delta front reaches the thick salt layer and differential loading promotes basinward salt flow, even upslope. On the western side of the delta, downslope gliding of the sediment-salt sequence toward the Herodotus Basin is driven by the elevation gradient toward the deepest part of the basin. Our analysis shows that salt squeezing by differential loading was previously overestimated in the Eastern Mediterranean and raises the need to carefully map the boundary of salt basins prior to any interpretation. This conclusion is especially relevant in young basins where deltas and shelves have not propagated far enough into the basin. [ABSTRACT FROM AUTHOR]

Sedimentological and sedimentary petrographic investigations of the Hamitabat Formation sandstones exhibited a huge submarine fan formation in the northwest of Thrace Basin. In this study reservoir properties of Hamitabat Formation were found out according to sedimentological storage, sedimentary petrographic and petrophysical properties of the sandstone-core samples taken from 16 wells in the northwest of the Thrace Basin. According to analyses of the lithology, sedimentologic structure, texture and sedimentary petrography of the well samples the Hamitabat Formation sandstones were separated into three distinct lithofacies (A, B, and C). Lithofacies A sandstones exhibit coarse grain sizes (0.5-1.0 mm), smooth-point grain contact, subrounded-subangular grains, moderate-bad sorting, and corresponds to upper part of submarine fan formation. Lithofacies B sandstones exhibit medium grain sizes (0.25-0.5 mm), subrounded-rounded grains, concave-convex grain contact, moderate-good sorting, and corresponds to middle part of submarine fan formation. Lithofacies C sandstones exhibit very fine grain sizes (0.12 mm<) corresponds to lower part of submarine fan formation, and nonreservoir facies. Lithofacies A sandstones have medium quality reservoir property due to abundance of cross bedding, higher clay content, less pore areas formed by secondary dissolution, low permeability (0.1-10 mD) and porosity (6-12%). Lithofacies B sandstones have better reservoir properties than Lithofacies A due to fewer clay content, large pore throat, high permeability (16-104 mD) and porosity (15-24%). According to thisstudyhydrocarbons come from Hamitabat Formation Lithofacies B sandstones in the Thrace Basin. Mid part (Lithofacies B) of the Hamitabat Formation submarine fan sandstones have higher hydrocarbon potential than its upper part (Lithofacies A) [ABSTRACT FROM AUTHOR]

Shelf‐margin clinothem successions can archive process interactions at the shelf to slope transition, and their architecture provides constraints on the interplay of factors that control basin‐margin evolution. However, detailed textural analysis and facies distributions from shelf to slope transitions remain poorly documented. This study uses quantitative grain‐size and sorting data from coeval shelf and slope deposits of a single clinothem that crops out along a 5 km long, dip‐parallel transect of the Eocene Sobrarbe Deltaic Complex (Ainsa Basin, south‐central Pyrenees, Spain). Systematic sampling of sandstone beds tied to measured sections has captured vertical and basinward changes in sedimentary texture and facies distributions at an intra‐clinothem scale. Two types of hyperpycnal flow‐related slope deposits, both rich in mica and terrestrial organic matter, are differentiated according to grain size, sorting and bed geometry: (i) sustained hyperpycnal flow deposits, which are physically linked to coarse channelized sediments in the shelf setting and which deposit sand down the complete slope profile; (ii) episodic hyperpycnal flow deposits, which are disconnected from, and incise into, shelf sands and which are associated with sediment bypass of the proximal slope and coarse‐grained sand deposition on the medial and distal slope. Both types of hyperpycnites are interbedded with relatively homogenous, organic‐free and mica‐free, well‐sorted, very fine‐grained sandstones, which are interpreted to be remobilized from wave‐dominated shelf environments; these wave‐dominated deposits are found only on the proximal and medial slope. Coarse‐grained sediment bypass into the deeper‐water slope settings is therefore dominated by episodic hyperpycnal flows, whilst sustained hyperpycnal flows and turbidity currents remobilizing wave‐dominated shelf deposits are responsible for the full range of grain sizes in the proximal and medial slope, thus facilitating clinoform progradation. This novel dataset highlights previously undocumented intra‐clinothem variability related to updip changes in the shelf process‐regime, which is therefore a key factor controlling downdip architecture and resulting sedimentary texture. [ABSTRACT FROM AUTHOR]

The Baranof Fan is one of three large Alaska deep-sea fans that preserve sedimentary records reflecting both tectonic and climatic processes. However, lack of drill sites in the Baranof Fan makes the depositional history across the southeastern Alaska margin still poorly understood. Sequence correlation from the adjacent Surveyor Fan to the Baranof Fan provides updated age constraints on the Baranof Fan evolution history. Results show that both the Baranof and Surveyor Fans are dominantly glacial and initiated ca. 2.8 Ma and expanded rapidly since ca. 1.2 Ma in response to the major glaciation events; these results place the deposition of the Baranof Fan younger than previously thought (ca. 7 Ma). The glacially influenced Baranof Fan contains two sub-fans that are laterally stacked with their depocenters migrating southeastward. Each sub-fan developed multiple channels that young southeastward as channel avulsion, coevolution, and tectonic beheading progressed over the past ~2.8 m.y. Tectonic reconstruction suggests that the Baranof Fan is sourced from the Coast Range via shelf-crossing troughs near the Chatham Strait and Dixon Entrance and thus represents a major outflow for the Cordilleran Ice Sheet during glaciations; the Chatham Strait is the major conduit that has fed most of the Baranof Fan channels. Comparatively, the Surveyor Fan is sourced predominantly from the St. Elias Range where a confluence of orogenesis and glaciations are a coupled system and only partly from the Coast Range via the Icy Strait. It is concluded that the formation and expansion of the Cordilleran Ice Sheet has determined the timing of the Baranof Fan deposition, yet Pacific--North America strike-slip motion has influenced the Baranof Fan sedisediment distribution, as previously suggested, via a series of southeastward avulsing channels and resultant southeastward migration of deep-sea depocenters. [ABSTRACT FROM AUTHOR]

The accretionary wedge in the incipient arc‐continent collisional zone offshore southwestern Taiwan is rich in gas hydrates as inferred from reflection seismic data and the geochemical analyses of shallow sediments. In this study, 2D and 3D seismic data were used to investigate the role of structural factors including mud diapirism on the formation of gas hydrates and associated free gas in the Quaternary Lower Fangliao Basin, a semi‐enclosed slope basin situated on the upper accretionary wedge. Albeit limited drilling information on lithostratigraphy and petroleum potential in the area together with seismic reflection data show that mud diapirs have influenced the formation of bottom‐simulating reflectors (BSRs) and the distribution of gas hydrates and free gas. On reflection seismic profiles, five seismic facies were observed and are characterised by: stratified parallel reflections; contorted reflections; semi‐parallel, high‐amplitude reflections; oblique, continuous high‐amplitude reflections; and generally transparent reflections. These seismic facies were respectively interpreted as hemipelagic sediments, mass transport deposits (MTDs), sandstone‐rich turbidites, overbank deposits and mud diapirs. The gas hydrate stability zone (GHSZ) is characterized by (i) high amplitude reflections with an analogous phase to that of seafloor, possibly indicating potential porous sandstone‐rich turbidite reservoirs; (ii) BSRs showing polarity reversal relative to seafloor, suggesting higher impedance gas hydrates overlying lower impedance intervals with free gas; (iii) blanking reflections in fault zones, interpreted as gas‐bearing fluid conduits; (iv) strong reflections on the flanks of mud diapirs (e.g. flank drags) and above buried mud diapirs, demonstrating the presence of gas hydrates; (v) high amplitude reflections dragging on diapiric flanks with reversed phase to that of seafloor, indicating free gas ‐charged zones abutting mud diapirs; and (vi) the presence of focused advection and diffusion flow through mud diapirs and faults, which is interpreted to control the migration of thermogenic gas. Based on the distribution of seismic amplitude characteristics and reflection strength with respect to depth of the BSRs, hydrocarbon prospects can be divided into gas‐hydrate compartments above BSRs, free gas compartments above BSRs, and free gas compartments below BSRs. From a combination of geobody extraction and Monte Carlo simulation, the prospects appear to hold about 2048 Bcf (billion cubic feet) of total gas volume over a study area of 60 km2. These observations provide first‐order estimates of methane resources in the Lower Fangliao Basin offshore southwestern Taiwan. [ABSTRACT FROM AUTHOR]

The discovery of the super-giant Coral and Mamba gas fields in the offshore of Northern Mozambique provides a unique insight into the architecture of a new deep-water play-type. High-quality seismic and extensive well data from both fields shows that very clean (clay matrix-poor) sandstone reservoirs, with thickness >100 m and extended over tens of km can be formed by the syndepositional interaction of down-slope high-density turbulent gravity flows and across-slope bottom currents. This is recorded by: i) the marked asymmetry of submarine channels and lateral stacking in which top-of-fan seismic reflectors show a lateral transition from high to low amplitude response from axis to off-axis locations; ii) the occurrence of laterally-deviated lobe deposits, sediment waves and channel-associated drifts in the inferred bottom current direction; iii) the presence of very clean sandstones forming the bulk of the fan units and the consistent lack of interbedded fine-grained facies; iv) the occurrence of fine-grained and thin-bedded facies adjacent to the main fan axes, which are characterized by repeated transitions between ripples and parallel-laminated sandstones, mud-drapes, shale clasts and bi-directional cross-laminae in the same bed, indicating intense traction and velocity pulsations. This association forms a mixed depositional system, in which only the basal and coarse-grained part of the turbidity current load is deposited and preserved in the axial part of the system, whilst all the finer-grained sediments are pirated from the turbulent cloud by laterally flowing bottom currents and deposited in the adjacent sediment drifts. The inferred process results in exceptionally high quality reservoirs whose architectural and facies models were confirmed by the appraisal campaign and production well tests and incorporated into the reservoir model. The results of this study indicate a significant exploration potential in similar geological settings and the definition of a potential new play type, that could lead to the reinterpretation of existing deep-water datasets. • First insight of the Area 4 in northern Mozambique and the Coral Field. • New deep-water play-type: very thick, clean and extensive reservoir sandstones. • Deposits formed by syndepositional interaction of bottom currents and gravity flows. • High quality dataset composed of well logs, cores and 3D seismic. • A facies tract related to deposits affected by bottom currents is proposed. [ABSTRACT FROM AUTHOR]

Processes occurring at the grounding zone of marine terminating ice streams are crucial to marginal stability, influencing ice discharge over the grounding‐line, and thereby regulating ice‐sheet mass balance. We present new marine geophysical data sets over a ~30×40 km area from a former ice‐stream grounding zone in Storfjordrenna, a large cross‐shelf trough in the western Barents Sea, south of Svalbard. Mapped ice‐marginal landforms on the outer shelf include a large accumulation of grounding‐zone deposits and a diverse population of iceberg ploughmarks. Published minimum ages of deglaciation in this region indicate that the deposits relate to the deglaciation of the Late Weichselian Storfjordrenna Ice Stream, a major outlet of the Barents Sea–Svalbard Ice Sheet. Sea‐floor geomorphology records initial ice‐stream retreat from the continental shelf break, and subsequent stabilization of the ice margin in outer‐Storfjordrenna. Clustering of distinct iceberg ploughmark sets suggests locally diverse controls on iceberg calving, producing multi‐keeled, tabular icebergs at the southern sector of the former ice margin, and deep‐drafted, single‐keeled icebergs in the northern sector. Retreat of the palaeo‐ice stream from the continental shelf break was characterized by ice‐margin break‐up via large calving events, evidenced by intensive iceberg scouring on the outer shelf. The retreating ice margin stabilized in outer‐Storfjordrenna, where the southern tip of Spitsbergen and underlying bedrock ridges provide lateral and basal pinning points. Ice‐proximal fans on the western flank of the grounding‐zone deposits document subglacial meltwater conduit and meltwater plume activity at the ice margin during deglaciation. Along the length of the former ice margin, key environmental parameters probably impacted ice‐margin stability and grounding‐zone deposition, and should be taken into consideration when reconstructing recent changes or predicting future changes to the margins of modern ice streams. [ABSTRACT FROM AUTHOR]

Multibeam bathymetry, coupled with seismic reflection profiles and sediment cores, was collected to understand the sediment process mechanisms for active onshore-offshore sediment transfer system from coastal erosion to nearshore transfer of sediment into a submarine channel and fan system. Savary Island in the northern Salish Sea of British Columbia, Canada, emerged immediately after deglaciation and became exposed to winter storms that began a continual modification of the island. Subsequent to coastal erosion, sediments are moved from the south side of the island, by strong tidal currents and longshore drift, to the island's north side. The mobilized sands are then entrained into and swept down submarine channels during gravity flows, likely a response to enhanced hydrodynamic tidal flow. Downslope progradation within the channels is primarily a result of downslope migrating submarine dunes that transfer sand to small submarine fans. Further transport beyond the channels into the deeper basin occurs via turbidity flows that have been active throughout the late Holocene. The prospect for Savary Island is grim, as this sediment transfer system will likely continue until the island disappears altogether. [ABSTRACT FROM AUTHOR]

As a high-precision survey method, seismic surveying has been increasingly applied to inland water research, although its application to artificial reservoirs has remained limited. As a special artificial water body, reservoirs have important effects on the fluvial transport of material from land to ocean, and inevitably have complex terrain which can complicate and distort the results of seismic surveys. Therefore, there are still some problems need to be resolved in the application of seismic surveys in reservoirs with complex terrain. For this study, the Dongfeng Reservoir located in the upper reaches of the Wujiang River was chosen as an example to test the seismic survey method. Our testing showed that (1) because of the complex underwater terrain, the signal-to-noise ratio of the echo signal in canyon reservoir is low, making it difficult to determine sediment layers thicknesses in some areas; and (2) due to the large spatial heterogeneity of sediment distribution, insufficient density of cross-sections can lead to inaccurate interpolation results. To improve the accuracy of calculations, a mathematical method was used. Ultimately, the total burial mass of sediment was estimated at 2.85 × 107 tons, and the average burial rates of total organic carbon, total phosphorus, and total nitrogen were estimated at 0.194, 0.011, and 0.014 g cm−2 year−1, respectively. These values were close to the results of previous studies and hydrographic station data, indicating that seismic survey can be a reliable and efficient method for the mapping of reservoirs. [ABSTRACT FROM AUTHOR]

In recent years, shallow-marine fans have attracted considerable attention because they may serve as valuable targets in hydrocarbon exploration. By integrating 3-D seismic, well log, core, and other measured data, this study analyzed the sedimentary characteristics and factors controlling the deposition of shallow-marine fans in Member #1 of the Huangliu Formation in the Yinggehai Basin. Four depositional elements were recognized in the channel-lobe complexes (CLCs), channel-fill sandy debrites, channel-fill turbidites, sand-rich lobe deposits and mud-rich lobe deposits. The channel-fill sandy debrites, which are characterized by low root-mean-square (RMS) amplitude in plan view and deep V-shaped reflections in seismic profile, are commonly located in the internal regions of CLCs. They have widths ranging from 1 to 2 km and single sandbody thicknesses exceeding 25 m. A cored interval from a channel-fill sandy debrite comprising several ungraded sand units revealed massive fine-grained sandstones with floating mud clasts and muddy rip-up clasts. In contrast, the channel-fill turbidites are characterized by low or high RMS amplitude in plan view and shallow V-shaped or vermiform-shaped reflections in profile. They have a small-size frontal splay at the terminus, thus forming a lobe-channel-lobe depositional style. The width of a channel-fill turbidite is usually less than 0.5 km, and the single sandbody thickness is no more than 20 m. A cored interval of channel-fill turbidite consisted of very fine-grained sandstones containing incomplete Bouma subdivisions T a –T b. The sand-rich and mud-rich lobe deposits are characterized by high RMS amplitude and low RMS amplitude with continuous sheet reflection patterns, respectively. The deposition of the shallow-marine fans was significantly influenced by sea-level fluctuations and paleogeomorphology. When sea level fell rapidly, gravity flows with higher erosive energy and velocity tended to form widely developed large-scale channel-fill sandy debrites and sand-rich lobe deposits. When sea level rose, small-scale channel-fill turbidites were dominant because of relatively decreased gravity flow energy. Distinct variations of reservoir characteristics, including mean grain size, mud content, and pore-throat radius, were controlled by sea-level fluctuations. From the period of rapid sea-level fall to the period of rising sea level, the gravity flows may have been increasingly diluted due to sufficient mixing with ambient seawater, resulting in a gradual transformation from sandy debris flows into turbidity currents. In addition, changes in gradient caused by irregular paleogeomorphology may have significantly triggered different depositional styles. With a steeper gradient, the CLC is dominated by a channelized-lobe depositional style; however, a lobe-channel-lobe depositional style prevails under a gentler gradient condition. Taking the reservoir characteristics and depositional styles into consideration, it is suggested that the sandy debrites, with better physical properties, constitute favorable hydrocarbon reservoir intervals. The shallow-marine fans in this study may serve as a distinctive analogue to similar gravity flow deposits in other basins worldwide. • Four depositional elements were recognized in the channel-lobe complexes. • Each depositional element shows distinctive seismic, well log, and core expressions. • Depositional variations are controlled by sea level fluctuations. • The irregular paleogeomorphology exert a fundamental control over depositional styles. • Sandy debrites represent a preferable hydrocarbon unit than turbidites. [ABSTRACT FROM AUTHOR]

The geomorphological evolution and sediment dispersal processes of the Liaodong Bay Depression (LBD), a strike-slip and extensional composite basin in the Dongying Formation, were studied using 3D seismic, drilling, and logging data in an attempt to understand the diversity of sand-controlling factors and the complexity of the sand dispersal processes. The LBD was mainly supplied by sediments from the eastern side, which originated in the Yanshan Fold system (comprising the Dashi River, Liugu River, and Lin River systems) and sediments from the western side, which originated from the Jiaoliao Uplift system (comprising the Daqing River and Fuzhou River systems). Different sediment provenances had various sediment supply capacities depending on the composition of the source rocks. Sediments were injected into the basin through the channels identified from two interpreted southwest-to northwest-orientated seismic sections. Strata of the Dongying Formation could be divided into three sequences, and comprised shallow-deep lacustrine deposits, braided river delta deposits, fan delta deposits, and sublacustrine fan deposits. Based on the established sequence stratigraphic framework, the strata thickness distribution and sequence of geomorphological evolution could be restored from 3D seismic data of the LBD. By analyzing the distribution and migration of depocenters and the distribution of channels, sediment pathways in the basin could be determined under high flux sediment supply. In terms of five interpreted seismic sections from north to south, we demonstrated that in addition to immense changes in tectonic depositional style in the eastern areas of the basin, the sediment dispersal processes in different areas exhibited prominent discrepancies in sediment accumulations from diverse depositional systems. Tectonic activities, efficient sediment provenance, distribution of channels, and sequence geomorphology jointly controlled the sediment dispersal processes in the deposition areas and determined the potential reservoir distribution. • Geomorphological evolution and sediment dispersal of a bay depression was studied. • Strata thickness and sequence-geomorphology was restored from 3D seismic data. • Distribution of incised valleys and sediment pathways in the basin were determined. [ABSTRACT FROM AUTHOR]

This paper reports the discovery of glacial deposits of likely Siderian--Rhyacian age (2.58-2.06 Ga) in South America (Carajás Basin, Brazil), thereby expanding the potential reach of Paleoproterozoic glaciations to the Amazonian craton for the first time. Glacially derived diamictites are stacked within a hitherto unrecognized ~600-m-thick siliciclastic succession, here named the Serra Sul Formation. Well-preserved textures, with evidence of glaciotectonism and ice rafting, indicate deposition in a coastal subglacial to glacial-fed submarine fan system, in which the immediately underlying units (banded iron formation and volcanic rock) were the main source and bedrock. The Serra Sul diamictite may be correlated with any of the known Paleoproterozoic glaciations, or with none of them. [ABSTRACT FROM AUTHOR]

This study details sedimentary and compositional characteristics of the Middle to Late and Early Pleistocene calcareous clay units recovered from Site U1453 in the middle Bengal Fan. The sedimentary characteristics reveal that the calcareous clay units consist of calcareous hemipelagic muds and terrigenous hemiturbidite muds which represent intervening periods of hemipelagic sedimentation sensu stricto and a slow sedimentation from suspension clouds of low-concentration turbidity currents on the fan surface, otherwise dominated by sand and mud turbidites. Variations in compositions, such as organic and inorganic carbon contents and δ13C of bulk organic matters of the calcareous hemipelagic muds, indicate the glacial-interglacial climate forcing of carbonate dissolution, surface marine productivity, and sources of particulate organic matters in the middle Bengal Fan during the Middle to Late Pleistocene. The glacial-interglacial climate forcing on hemipelagic sedimentation seems to be much obscure during the Early Pleistocene because of dilution by terrigenous clay inputs. Grain-size distribution of bulk sediments suggests the presence of coarse foraminifer and finer nannofossil modes in the calcareous clay units and the size of dominant foraminifer species could have been finer in the Early Pleistocene. [ABSTRACT FROM AUTHOR]

Fluid migration within the sedimentary column contributes significantly to slope failure and pockmark formation and can be an effective triggering mechanism to generate submarine landslides. Pockmarks are thus commonly listed among geohazards. Contrary to these accepted notions, we propose here an alternative view of pockmarks with an example from the Eastern Niger Submarine Delta: Pockmarks and associated chimneys may increase or modify the shear strength of sedimentary layers and locally enhance seafloor stability. The analysis of two 3D seismic volumes shows that a landslide deposit divides into two branches around a cluster of three pockmark chimneys, interpreted to impede its further development. The morphological characteristics of a slide constrained by fluid seepage features show the potential role of fluid escape in marine sediment strengthening. [ABSTRACT FROM AUTHOR]

The Belaga Formation is a deep marine turbidite interpreted in relation to a submarine fan and therefore a prospect worth evaluating. The scope of this paper will focus on the shales from the thick sedimentary sequence of the Belaga Formation (Upper Cretaceous to Eocene) consisting of five (5) members in Central Sarawak, Malaysia, of which attention is given to the depositional environment and clay minerals as factors to consider as predictive tools for organic matter richness and gas storage capacity using the spectral gamma ray method using Thorium (Th), Potassium (K) and Uranium (U) as indices for inferences. A mineralogical chart of Th/K (ppm/%) indicates that the dominating clay minerals of the shales are mixed-layer types. The Th/U as a redox indicator is used to assert that the shales are of anoxic conditions of deep-marine environments. Despite the relatively high insoluble Th values (9.93-20.13) ppm, the presence of U in substantial amounts, which only occurs in reducing conditions where it is preserved as a lower insoluble valence (U4+) explains for the low Th/U values ranging between (1.86-4.57) ppm/ppm of the fifty-eight analyzed shale samples. The overall Th/U value of the evaluated shales remain less than 7, where Th/U < 7 is suggestive of marine sediments, grey and green shales, whereas Th/U < 2 is indicative of marine black shales of reducing conditions. The 30Ma interval of sediment deposition of the Belaga Formation Eocene recorded varied climatic fluctuations influential to clay minerals contained in the shales and ascribe the paleoweathering state of the shales, which from the standard imitative ternary plot of normalized K-U-Th of shales from Northern America address the shales of the Belaga Formation as of deep weathering residuum. [ABSTRACT FROM AUTHOR]

A vast accumulation of high‐saturation gas hydrates has been hypothesized to be present in the central Gulf of Mexico; the interpretation was based on seismic travel time deficits underlying high velocity Pleistocene coarse‐grained turbidites. While these deposits could represent one of the largest‐known gas hydrate reservoirs, some workers have concluded that lithologic contrasts are instead the primary cause of observed velocity pull‐ups. Here, using cuttings and core, well logs, and seismic data from the Mississippi Fan, we demonstrate that lithologic differences can account for a maximum of ~6–33% of the total observed travel time deficits. This conclusion supports the previous interpretation of a gas hydrate province, provides a basis for distinguishing the cause of velocity pull‐ups, and suggests that the future of gas hydrate exploration should continue to include the coarsest‐grained component of the Earth's largest near‐seafloor submarine fans. Plain Language Summary: A large accumulation of gas hydrates, which are frozen hydrocarbons located in near‐surface settings, was recently interpreted to exist in the central Gulf of Mexico; the subsurface deposit was inferred on the basis of artifacts related to increased sound wave velocities (i.e., travel time deficits). Although other factors, such as lithologic differences, also can produce changes in the speed of sound, the observed contrasts are too great to be explained by such variations. This observation supports the initial claim of the presence of a vast gas hydrate accumulation and suggests that similar settings worldwide may contain comparable frozen gas‐bearing deposits. Key Points: Petrophysical analyses establish P wave velocity trends with depth in the central Gulf of MexicoTravel time deficits from Mississippi Fan sediments are compared to recently identified seismic velocity pull‐upsBecause lithologic contrasts cannot explain the majority of observed velocity artifacts, a gas hydrate interpretation is supported [ABSTRACT FROM AUTHOR]

Repeat multibeam bathymetric surveys conducted in 2004, 2005 and 2018 show that seven slope-confined canyons on the continental slope of the Pearl River Mouth Basin, South China Sea, were dominated by large volume, widespread erosion. Erosion volumes were up to 3.4 times greater than deposition volumes. Erosion-dominated areas of the canyons are up to 2.3 times greater than areas dominated by deposition. Average rates of erosion (ranging from 0.7 to 0.8 m/yr) were greater than average rates of deposition (ranging from 0.5 to 0.8 m/yr). In plan view, the erosion-dominated zones exhibit two characteristic shapes: (1) linear, found mainly in upper canyon reaches, distributed predominantly along canyon axes and at the base of eastern canyon walls, and; (2) blocky, found mainly in lower canyon reaches, widely distributed along the steep canyon walls and on lower-canyon interfluves. The deposition-dominated zones are scattered along canyon floors and walls. Seismic reflection data show lateral shifts of canyon fill deposits through time, indicative of longer-term eastward canyon migration. The linear erosion-dominated zones may be attributed to erosive turbidity currents triggered by energetic internal solitary waves shoaling on the shelf. The eastward canyon shifts were likely induced by rapid near-bed eastward currents generated mainly by westward propagating powerful internal solitary waves of depression. The widespread erosion in the deeper canyon areas and interfluves is likely a consequence of slope instabilities associated with the presence of gas hydrates. This study indicates that active sedimentary processes can occur in slope-confined canyons even during sea level highstands. Local, site-specific oceanographic and geological features (e.g., internal solitary waves, gas hydrates) can significantly increase sedimentary activity in and around submarine canyons. • Seven slope-confined canyons in the northern South China Sea were dominated by erosion, 2004–2018 • Ratios of erosion-dominated to deposition-dominated area in the canyons ranged from 1 to 2.3 • Ratios of eroded to deposited sediment volumes ranged from 1.2 to 3.4 • In the upper canyon reaches, internal solitary waves resulted in the triggering of turbidity currents. • In the lower reaches, gas hydrate activity likely caused submarine slope instabilities. [ABSTRACT FROM AUTHOR]

Turbiditic flysch units of the Rajang Group form a large crescentic belt of deformed strata in central Borneo. Unfortunately, our understanding of its bed type characteristics and depositional setting is very poor. Here, we present a detailed bed type analysis of the Palaeocene to middle Eocene Kapit and Pelagus members of the Belaga Formation, based on detailed investigations of recent road‐cut exposures around Sibu, Sarawak, Malaysia. Five bed types are identified from the studied sections, representing deposition from turbidity currents, debris flows, and flows that show turbulent and laminar characteristics. The Belaga Formation deposits are divided into four bed type associations based on bed type assemblages, bed geometry, degree of bed amalgamation, vertical grain size, and bed thickness trends, for example, lobe axis, lobe off‐axis, lobe fringe, and slump. Hybrid event beds (HEBs) are not restricted only to the lobe fringe but are also a common element of the lobe axis sub‐environment in the Belaga Formation system. Their common occurrence in a proximal location in the lobes is probably due to enhanced seafloor erosion and rapid deceleration due to loss of confinement at the channel lobe transition further up‐dip. Evidence such as bidirectional ripple cross‐lamination in thin‐bedded turbidites and variable palaeocurrent orientations suggest a complex depositional topography, which also suppressed flow turbulence and promoted deposition of hybrid event beds in proximal locations through deflection and deceleration of incoming flows by confining counter slopes. Similar bed type assemblages within the slump and lobe deposits indicate a local origin for the slumps. Localized failures can form on low gradient slopes developed in tectonically active basins with complex topography. [ABSTRACT FROM AUTHOR]

The performance of the regenerative indirect evaporative cooler (RIEC) highly depends on ambient temperature and humidity. To maintain indoor thermal comfort, proper control strategy is essential. Previous research indicates that high–low (H-L) control by using multispeed technology is superior to the conventional on–off control in terms of energy consumption and thermal comfort. Under H-L control, a fan switches between a high speed and a low speed. The high speed is determined by the peak load. However, the selection of low speed involves a great sense of subjectivity. Therefore, the influence of low speed on system performance is comprehensively investigated and an optimal low speed to high speed ratio (L/H) is determined. An optimization method is proposed by considering annual energy consumption, predicted mean vote, temperature fluctuation, and switch frequency of fan speed. Case studies have been conducted in some typical hot and arid regions. The results show that better thermal comfort can be provided under lower L/H from the aspects of high control precision and low temperature fluctuation. The switch frequency of fan speed and the annual energy consumption first decrease and then increase with the increment of L/H. The optimal L/H is between 0.2 to 0.3 from a year-round perspective and with comprehensive consideration. [ABSTRACT FROM AUTHOR]

Marine carbonate δ13C and δ18O values are commonly utilized as indicators of past climate and are thought to record primary seawater conditions. However, these minerals can be altered following deposition and burial, overprinting the primary signal to reflect subsurface conditions. Whereas the influence of post-depositional alteration is widely understood in carbonate-dominated sediments (Swart, 2015), the influence has not been as widely studied in mud-rich settings. This study analyzed the carbonate δ13C and δ18O values from carbonate intervals in the Late Pennsylvanian Wolfcamp D shale unit in the Midland Basin to evaluate the impact of post-depositional alteration on the interpretation of stable isotope compositions of carbonates in a mud-rich depositional environment. Here we show the importance of using multiple indicators to fully evaluate the impact of post-depositional alteration on the interpretation of the marine carbonate δ13C and δ18O values in mud-rich environments. The extent of diagenesis in the Wolfcamp D was primarily controlled by fluctuations in benthic redox chemistry, which controlled sulfate reduction and the preservation of organic matter. These processes influenced the extent of carbonate cementation in the bacterial sulfate reduction zone and during deep-burial, making the carbonates unreliable for intra-basinal correlations. The results of this study were incorporated into a conceptual model that can likely be applied as a framework for other studies in mud-rich depositional environments. • Evidence for both early and deep burial diagenesis was recorded in the carbonates. • Magnitude of gravity flow deposition influenced carbonate diagenesis. • Dolomitization likely occurred through brine-induced diagenesis. • Dolomitization and diagenesis were heterogeneous across the Midland Basin. [ABSTRACT FROM AUTHOR]

In recent years it has become clear that many shallow‐marine heterolithic and mudstone‐dominated successions are deposited as mud belts forming part of subaqueous deltas that are related to major fluvial sources either upstream or along shore. Here the Havert Formation is presented as an ancient example of this kind of system. The Havert Formation in the south‐western Barents Sea represents shelf margin clinoforms consisting predominantly of heterolithic deposits. Sediments were mainly derived from the east (Ural Mountains), but a smaller system prograded northward from Fennoscandia. The Havert Formation holds a lot of interest due to: (i) its stratigraphic position, directly above the Permo–Triassic boundary and contemporaneous to the emplacement of the Siberian Traps; (ii) the fact that it represents the first siliciclastic input in the south‐western Barents Sea and it shows interaction between Uralian‐derived and Fennoscandian‐derived sediments; and (iii) its hydrocarbon potential. This study is focused on a detailed sedimentological analysis of cored intervals of the (Ural‐derived) Havert Formation, in combination with seismic interpretation, well‐log correlations and palynological analysis of the Havert and overlying Klappmyss formations. The cored intervals belong to the shelf environment of the Havert shelf‐margin clinoforms (300 to 500 m thick). This sedimentological analysis distinguishes six facies associations, spanning from tidally‐influenced channels at the shoreline to mud‐rich subaqueous platform and foresets of the subaqueous delta. Seismic lines and well‐log correlations show the larger‐scale evolution of the Ural‐derived Havert Formation, characterized by episodes of low‐accommodation and high‐accommodation. The palynological analyses provide the first detailed study of the Havert Formation in the Nordkapp Basin, revising its depositional age in the region as Induan to early Olenekian (Smithian). Furthermore, they strengthen the environmental interpretation; palynofacies present on the shelf record flora of tidally‐influenced coastal plains, whereas the palynofacies in the deep‐water slope contain only amorphous organic matter. [ABSTRACT FROM AUTHOR]

Carbonate sediments of nonglacial Cryogenian (659 to 649 Ma) and early Ediacaran (635 to 590 Ma) age exhibit large positive and negative δ13Ccarb excursions in a shallow-water marine platform in northern Namibia. The same excursions are recorded in fringing deep-sea fans and in carbonate platforms on other paleocontinents. However, coeval carbonates in the upper foreslope of the Namibian platform, and to a lesser extent in the outermost platform, have relatively uniform δ13Ccarb compositions compatible with dissolved inorganic carbon (DIC) in the modern ocean. We attribute the uniform values to fluid-buffered diagenesis that occurred where seawater invaded the sediment in response to geothermal porewater convection. This attribution, which is testable with paired Ca and Mg isotopes, implies that large δ13Ccarb excursions observed in Neoproterozoic platforms, while sedimentary in origin, do not reflect the composition of ancient open-ocean DIC. [ABSTRACT FROM AUTHOR]

Earth to air heat exchanger is a very old technique used 3000 years B.C in arid regions where that was called Qanat. In the present experimental study, the potentials of earth to air heat exchanger to provide thermal comfort for winter weather conditions in South west of Algeria described as arid region are investigated. An EAHE made of 66 meter of PVC tube and buried at 1.5 meter underground in agriculture zone equipped with 33 W fan was studied. Thermal and hygrometric analysis of air passing inside the tube form inlet to outlet was conducted. The results show the system was able to create two thermal regimes: heating regime with a gain of 13 °C (from 00h to 11h and from 17h to 23h) and cooling regime (from 12h to 16h) with 6 °C in the same day. Relative humidity was reduced by 32 % of 90 % of studied cases which stops the development of micro-organism and reducing Internal Air Quality. [ABSTRACT FROM AUTHOR]

Highlights • An experimental procedure to compare baseline working conditions and a set of failures is presented. • One advanced technique to analyze the signature or vibrating spectra for a Sirocco fan is used. • A Symmetric Dot Point Technique is applied to a centrifugal fan operating conditions. • Different vibrating levels are obtained and depict the overall working framework of the fan. • The technique to the particular application opens new possibilities for maintenance protocol. Abstract Sirocco fan units, also known as squirrel cage fans, are usually installed at the air conditioning systems of vehicles used in public transport. They must provide an accurate ventilation flow rate, with high efficiency and performance, but also without operative problems like underperforming, outages or breakdowns, which usually lead to compromise the comfort and quietness of the passengers. Due to their heavy duty, they are susceptible of such problems which finally cause poor ventilation, magnified in highly crowded situations, and important noise generation with uncomfortable vibrations. Periodic maintenance and regular monitoring are thus essential to control that the fan operative range ensures a correct operation. This paper deals with a series of working failures, typically encountered in industrial applications with Sirocco fans, like impeller unbalances, obstructed channels or blocked inlets. A database with vibration signals has been measured experimentally to obtain the forced response of the fan as a function of the flow rate for different troubled scenarios. Following, a Symmetrized Dot Pattern (SDP) technique, that transforms the temporal waveforms into polar maps, is employed to generate dot patterns which can discriminate between different working conditions and failures, allowing an easy visual identification. The final objective is to show the potentiality of this technique as a fault diagnosis methodology for typical squirrel cage fans, providing optimal parameters for its use. The results obtained are also compared with other diagnosis techniques, previously employed by the authors, for a complementary analysis of the vibrating condition of these centrifugal fans. [ABSTRACT FROM AUTHOR]

Year-round and efficient production for crop products of high yield, quality and cleanliness is the development trend of the Chinese solar greenhouse (CSG). However, this is limited by unfavorable climate conditions inside the CSG, such as high air temperature in warm seasons. The fan-pad cooling system, normally adopting negative pressure ventilation, has been widely used for greenhouse cultivation. But it generates a large air temperature gradient in greenhouse, limits the greenhouse dimensions. Above deficiencies are more serious in the CSG. Because CSG always has a long distance between the sidewalls, fans and gaskets are installed separately on the sidewalls. In order to overcome the limitations of negative fan-pad cooling system and improve ability of the CSG in coping with high temperature, a positive pressure fan-pad cooling system (PPFPCS) was designed in this study. By using this system, the cold and humid air enters the CSG from bottom of south roof, and then hot air leaves the CSG through roof vents. Performance of the PPFPCS was tested in a CSG without crops in Beijing area during summer. Results showed that in typical summer hot days, the PPFPCS cooperating with external shading net could decrease mean air temperature of the CSG experimental area to 30.7-33.4 °C, which was lower than that in the CSG contrast area using natural ventilation combination with external shading net by 5.4-11.1 °C. Air temperature of the CSG experimental area was also lower than that outside the CSG with a temperature difference of 2.4-5.4 °C. Nevertheless, both natural and mechanical ventilations were tested to have limited cooling capacity to meet climate requirement for CSG cultivation. The PPFPCS could also decrease the CSG air temperature at night, but had a poorer performance in comparison with daytime cooling due to the smaller vapor pressure deficit (VPD). The contrast area of CSG encountered an extreme low air humidity state with mean VPD of 3.4-6.1 kPa. PPFPCS could effectively alleviate low humidity stress: the average relative humidity in CSG experimental area was between 49.8% and 62.3%, which was 13.6% - 21.2% higher than that in CSG control area and 13.6% - 24.6% higher than that in outdoor area. Wind velocity inside the CSG experimental area ranged from 0.35 to 1 m/s, which indicated a relative uniform air flow distribution. Cooling efficiency of the PPFPCS was about 91%, which was over 10% higher than that of the traditional negative pressure fan-pad cooling system. Low temperature of the PPFPCS circling water contributed to the high cooling efficiency. Average water consumption rate of the PPFPCS used for CSG cooling was 0.035-0.079 g/(m2·s) during the test. It had a positive linear correlation with VPD of outdoor air, that is drier outdoor air anticipates larger water consumption and better cooling performance. Both cooling load model of the CSG and selection method for fan-pad cooling system were derived. Cooling load model is the basis for capacity calculation of cooling equipment to be installed. Cooling load of the CSG in summer was 299.1 W/m2. Contribution ratios of convective heat transfer between north wall and indoor air, convective heat transfer between greenhouse floor with indoor air, hot air infiltration, as well as heat transfer between indoor and outdoor air though south roof, north roof and side walls were 11.0%, 73.3%, 1.3% and 14.4%, respectively. The maximum specific ventilation rate of the PPFPCS used for CSG cooling was recommended to be 0.067 m/s. This study can provide technical support for the application of PPFPCS in CSG cultivation and provide theoretical basis for the climate control of CSG production in summer. [ABSTRACT FROM AUTHOR]

On the basis of the actively controlled multiple-fan wind tunnel we designed, this paper proposes a latticed mode–based control strategy for the fan array. The so-called latticed mode is the overall topology of the working fans. In order to investigate the simulation ability of the latticed mode, several latticed modes are designed to analyze the temporal and spatial properties of generated wind fields. Airflow data under different latticed modes are measured using nine two-dimensional anemometers, and then, statistical indicators of wind speed and wind direction, as well as the spatial uniformity and complexity of generated wind fields, are calculated to analyze the characteristics of wind records. The results indicate that the distribution of active fans in the latticed mode has significant influence on the statistical properties and spatial evolutions of wind speed and direction. Besides, the latticed modes can regulate the spatial uniformity and complexity of the wind fields. The latticed modes with a high clustering degree of active fans can generate wind fields with low spatial uniformity and high complexity. In addition to the fan voltage and the rotation angle of swivel plates, the proposed latticed mode provides more possibilities for wind field simulation. [ABSTRACT FROM AUTHOR]

Submarine fans are the largest sediment accumulations on Earth and are key to study the sediment-transfer zone between terrestrial source area and deep-sea depositional sink. They provide information of past climate, tectonics, carbon global inventory, and can be prolific hosts for oil/gas resources. In this paper, we present, for the first time, an analysis of the entire Magdalena Submarine Fan (MSF), from the shelf break to the distal domain, based on ~224,000 km2 of multibeam bathymetry, as well as backscatter, subbottom profiler and regional/local seismic reflection data recently acquired in southwestern Caribbean Sea. The aim is to describe in detail the MSF morphology and depositional architecture, propose a fan segmentation landform assemblage, and determine its extent within the deep basin. Three fan segments are identified: upper, middle and lower fans. The upper fan extends from the coastline to a depth of ~3000 m. Its eastern sector is characterized by a canyon system off the present-day mouth of the Magdalena River, through which most of the sediments are transported downslope to be deposited in intra-slope basins bounded by structural highs of the South Caribbean Deformed Belt. The western upper fan is characterized by distinct channel-levee complexes that are partially removed by mass transport complexes that originated near the continental shelf edge. The upper to middle fan transition is marked by a decrease in regional gradient from 1° to about 0.3° and local relief, a change from large, irregular sediment waves to more regular waves that slowly decrease in amplitude downslope, and the appearance of erosional megascours. The middle fan bedform assemblage evidences the presence of a channel-lobe transition zone in this sector of the MSF, separating well-defined, upper fan channels from lower fan depositional lobes. The middle to lower fan transition occurs between ~3800 and ~3950 m and is defined by a further decrease in gradient and by a change from sediment waves to planar parallel-bedded reflectors on subbottom profiles. The lower fan extends to a maximum depth of ~4250 m and is characterized by an almost flat seabed (slope of 0.05°), interrupted by a few isolated bathymetric highs and low-relief channels (<5 m deep). The entire area of the lower fan is interpreted as an area of turbidity current deposition, with relatively sandy sediments in the south and west giving way to muddier sediments in the northeast, which could correspond to distal fan lobes. The identification of four regional seismic facies related to MSF sedimentation allowed us to constrain the fan extent in the southwestern sector of the Caribbean. Distally, within the Colombia Basin the fan terminates against areas of elevated seafloor (Kogi-Coyaima and Quimbaya seamounts, Aruzi and Ticuna hills, and Beata Ridge), which have acted as barriers to sedimentation. Nevertheless, it was determined that the MSF extends beyond the Colombia Basin and locally reaches the Lower Nicaraguan Rise. In this new scenario, we established that the MSF is much more extensive than previously recognized, with an area of ~237,000 km2, which puts it among the World's largest submarine fans. • The morpho-structure of the entire Magdalena Submarine Fan (MSF) is presented • Upper, middle and lower fan segments are proposed from diverse landform assemblages • Channel-levee complexes partially removed by extensive MTCs defines the upper fan • Middle fan, with sediment waves and megascours, is defined as sediment bypass area • Evidence of turbidity current sedimentation, with probable lobes, in the lower fan [ABSTRACT FROM AUTHOR]

The Upper Cretaceous Prairie Canyon Member of the Mancos Shale, Book Cliffs, Utah, contain outstanding examples of prodeltaic turbidity and hyperpycnal flow deposits. Sandstone‐rich, heterolithic and mudstone‐rich channel fills occur near the north‐west entrance to Tusher Canyon, Gunnison Butte and Bootlegger Wash. Mudstone‐rich and heterolithic‐rich hyperpycnal channel deposits are mostly unbioturbated, locally displaying a few specimens of Phycosiphon incertum, Protovirgularia dichotoma, Rosselia socialis, Schaubcylindrichnus coronus and Palaeophycus tubularis. Sandstone‐rich channel deposits consist of wave‐reworked turbidites and hyperpycnites, containing Helminthoidichnites tenuis, Lockeia siliquaria, Phycodes isp., Phycosiphon incertum, Protovirgularia dichotoma, Rosselia socialis, Skolithos linearis and Fugichnia. Scolicia isp. and Chondrites isp. occur locally. Strata along the south‐west entrance of Tusher Canyon record deposition in a prodelta turbidite lobe, but far from its axis. With the exception of a few specimens of Ophiomorpha isp., bioturbation is restricted to the top of the succession, where Curvolithus simplex, Gyrochorte comosa, Lockeia siliquaria, Palaeophycus tubularis and Ptychoplasma excelsum occur. Strata at Hatch Mesa record deposition in a hyperpycnal lobe, near to its axis. Sandstone beds include Curvolithus simplex, Gyrochorte comosa, Ophiomorpha nodosa, Palaeophycus tubularis, Phycosiphon incertum, Protovirgularia dichotoma, Ptychoplasma excelsum, Schaubcylindrichnus freyi, Skolithos linearis, large specimens of Rosselia socialis and indeterminate crustacean burrows. Chondrites isp. is present in the mudstone. High rates of both episodic and sustained sedimentation, degree of substrate consolidation, freshwater discharge and water turbidity are the most important stress factors in both channels and lobes. Taxonomic composition, uneven distribution of bioturbation through the successions, and overall low ichnodiversity help to distinguish these prodeltaic deposits from bathymetrically equivalent offshore strata in the same basin. Hyperpycnal flow deposits are formed in a wide variety of environmental settings, therefore displaying high ichnological variability. Such variability is summarized by characterising ichnofaunas from four different depositional settings: (i) lakes; (ii) shelf deltas; (iii) shelf‐edge deltas; and (iv) deep‐marine systems. [ABSTRACT FROM AUTHOR]

Sediment waves are commonly observed on the sea floor and often vary in morphology and geometry according to factors such as seabed slope, density and discharge of turbidity currents, and the presence of persistent contour currents. This paper documents the morphology, internal geometry and distribution of deep‐water (4000 to 5000 m) bedforms observed on the sea floor offshore eastern Canada using high‐resolution multibeam bathymetry data and seismic stratigraphy. The bedforms have wavelengths of >1 km but fundamentally vary in terms of morphology and internal stratigraphy, and are distinguished into three main types. The first type, characterized by their long‐wavelength crescentic shape, is interpreted as net‐erosional cyclic steps. These cyclic steps were formed by turbidity currents flowing through canyons and overtopping and breaching levées. The second type, characterized by their linear shape and presence on levées, is interpreted as net‐depositional cyclic steps. These upslope migrating bedforms are strongly aggradational, indicating high sediment deposition from turbidity currents. The third type, characterized by their obliqueness to canyons, is observed on an open slope and is interpreted as antidunes. These antidunes were formed by the deflection of the upper dilute, low‐density parts of turbidity currents by contour currents. The modelling of the behaviour of these different types of turbidity currents reveals that fast‐flowing flows form cyclic steps while their upper parts overspill and are entrained westward by contour currents. The interaction between turbidity currents and contour currents results in flow thickening and reduced sediment concentration, which leads to lower flow velocities. Lower velocities, in turn, allow the formation of antidunes instead of cyclic steps because the densiometric Froude number (Fr′) decreases. Therefore, this study shows that both net‐erosional and net‐depositional cyclic steps are distributed along channels where turbidity currents prevail whereas antidunes form on open slopes, in a mixed turbidite/contourite system. This study provides insights into the influence of turbidity currents versus contour currents on the morphology, geometry and distribution of bedforms in a mixed turbidite–contourite system. [ABSTRACT FROM AUTHOR]

Taking some steam flooding experimental area in the western depression of the Liaohe Basin in China as an example, it quantitatively evaluates the flow units of the sedimentary facies in fan delta front and analyzes the influences of the flow units on the development of the oilfields. Comprehensive analysis of multifarious data such as geology, core analysis and well logs indicates that porosity, permeability and FZI are key parameters for classification and evaluation of the reservoir flow units. Then using SPSS cluster analysis software platform, cluster analysis are conducted on reservoir physical properties of cored wells, and based on which discriminant analysis are performed to obtain the discriminant formula. The discriminant analysis of reservoir physical properties of the wells without core data is based on fine interpretation of well logging data. Combined with the results of cored wells, the classification and evaluation of the flow units has been completed in the target layer of ​​the whole study area. Finally the flow units are divided into four classes, namely, Class A, Class B, Class C and Class D. Classes A and B flow units represent high-quality reservoirs. The flow units are mainly controlled by sedimentation. Classes A and B are mainly sedimentary microfacies of underwater distributary channel and distributary mouth sand bar. The paper proposes five principles of judging the rationality of flow units, describes the development characteristics of different classes of flow units on section and plane, analyzes the influence of flow units on oilfield development and suggests countermeasures. Specially, in the process of steam flooding, target injection layers should be optimized and steam injection pressure should be effectively controlled to prevent steam channeling; when planning infill wells, injection and production wells should be deployed in the same class of flow unit to ensure good connectivity; the development of remaining oil should focus on Classes A and B flow units, and meanwhile pay more attention to the fine interpretation results of well logging data. • The classification and evaluation method of flow units combined with genetic analysis and clustering analysis. • Key parameters optimized for classification and evaluation of the reservoir flow units. • Five principles of judging the rationality of flow units. • Analyzing of the influences of flow units on oilfield development and suggests countermeasures. [ABSTRACT FROM AUTHOR]

Calcareous nannofossils found in the Cergowa beds of the Dukla and Fore-Dukla tectonic units in the Outer Carpathians indicate a time of deposition in the range of the NP23–NP24 nannoplankton zones of the Lower Oligocene. Nannoplankton assemblages reflect the paleoecological changes at the Eocene–Oligocene transition from: (i) a greenhouse to an icehouse climate; (ii) brackish to normal salinity suggesting open sea conditions, which were controlled by the Paratethys Basin closure followed by opening and connection with the Tethyan Ocean. The absence of nannofossils of NP25 zone, but their presence in the tectonic windows between 40 and 80 km to the west, shows that deposition of the Cergowa beds in the western part of the basin lasted longer than in the east. Occurrences of nannofossils indicating zones NP16 and NP21, found in the uppermost mudstone-rich parts of studied sections, may prove the remobilization and redeposition of sediments of this stratigraphic age. Potentially, eroded material could be derived from some of the following lithostratigraphic units: NP16 — the Hieroglyphic beds, Przybyszów sandstones and Upper variegated shales; NP21 — the Globigerina marls, Mszanka sandstones and sub-Chert marls and shales and/or fine-grained equivalent of these units. Reworked specimens derived from the older Mesozoic strata occur occasionally in various samples. [ABSTRACT FROM AUTHOR]

Rambatan Formation in the western part of North Serayu Basin, Brebes, Central Java, comprises generally flysch facies of turbidite sediments deposited in a deep marine environment. This formation is equivalent to Merawu Formation found in the eastern part of the basin and deposited in the environment of tidal flat to subtidal. The turbidite sediments were highly controlled by a rapid downward movement taking place continuously during Early to Late Miocene. The variation of the depositional environment has been the object of this research which aims to understand the sedimentation process of Rambatan Formation in this type locality with a modern turbidite approach. Rambatan Formation was deposited in N13-N19, as a deep marine sediment channel, turbidite, and deep marine tidal zone. The sedimentation was affected by gravity flow and bottom current. The sediments on N13-N14 were marked by turbidite sediments until Middle N17. The sediment supply increased on Middle N17, as a sediment filler on a channel marked by contourite mud layer (muddy slump) and debris flow, with sources from the north. The increase of sediment supply was followed by an environmental transformation from a deep marine channel into deep marine tidal area. In N19, the sediments were redeposited as turbidite sediment, starting with debris flow in Middle N18. [ABSTRACT FROM AUTHOR]

The current understanding of tsunamis generated by volcanic-island landslides is reliant on numerical models benchmarked against reconstructions of past events. As the largest historical event with timed tsunami observations, the 1888 sector collapse of Ritter Island, Papua New Guinea provides an outstanding opportunity to better understand the linked process of landslide emplacement and tsunami generation. Here, we use a combination of geophysical imaging, bathymetric mapping, seafloor observations and sampling to demonstrate that the Ritter landslide deposits are spatially and stratigraphically heterogeneous, reflecting a complex evolution of mass-flow processes. The primary landslide mass was dominated by well-bedded scoriaceous deposits, which rapidly disintegrated to form an erosive volcaniclastic flow that incised the substrate over much of its pathway. The major proportion of this initial flow is inferred to have been deposited up to 80 km from Ritter. The initial flow was followed by secondary failure of seafloor sediment, over 40 km from Ritter. The most distal part of the 1888 deposit has parallel internal boundaries, suggesting that multiple discrete units were deposited by a series of mass-flow processes initiated by the primary collapse. The last of these flows was derived from a submarine eruption triggered by the collapse. This syn-collapse eruption deposit is compositionally distinct from pre- and post-collapse eruptive products, suggesting that the collapse immediately destabilised the underlying magma reservoir. Subsequent eruptions have been fed by a modified plumbing system, constructing a submarine volcanic cone within the collapse scar through at least six post-collapse eruptions. Our results show that the initial tsunami-generating landslide at Ritter generated a stratigraphically complex set of deposits with a total volume that is several times larger than the initial failure. Given the potential for such complexity, there is no simple relationship between the volume of the tsunamigenic phase of a volcanic-island landslide and the final deposit volume, and deposit area or run-out cannot be used to infer primary landslide magnitude. The tsunamigenic potential of prehistoric sector-collapse deposits cannot, therefore, be assessed simply from surface mapping, but requires internal geophysical imaging and direct sampling to reconstruct the event. • Ritter Island's sector collapse provides an exemplar of volcanic tsunami hazards. • Deposit heterogeneity reflects erosion, secondary failure and a triggered eruption. • The volume of the distal deposit alone far exceeds the tsunamigenic failure. • A single catastrophic collapse led to stratigraphically complex distal deposits. • Accurate assessment of tsunami potential requires internal imaging and sampling. [ABSTRACT FROM AUTHOR]

Carboniferous glaciogenic strata (Itararé Gp.) in the southernmost Paraná Basin, Brazil exhibit soft-sediment deformation features previously interpreted as glaciotectonism. These sediments were studied in detail to confirm that they were deformed by ice and to assess the nature of the glaciation, depositional environments, and paleoclimate in this region during the Carboniferous. Five outcrops were described along a railroad transect that contains a conglomerate and diamictite facies with striated and faceted clasts, a medium sandstone facies, a fine grained silt/clay rhythmite and mudstone facies with dropstones and diamictite pellets, a sandy clinoform facies, and a folded sandstone with interbedded mudstone facies. The depositional environment for these sediments is interpreted as an outwash fan and fan delta from an ice-proximal, transitional terrestrial-to-estuarine setting. Rb/K values from the rhythmites reflect a transition from a freshwater to brackish environment and the Chemical Index of Alteration (CIA) of the rhythmites ranges from 65 to 73, reflecting a relative increase in the degree of chemical weathering through time. Deformation features include widespread folding, thrust faults, hydrofractures, décollement surfaces, and piggyback fold-thrust complexes. The deformation is interpreted as evidence of a push-moraine complex formed by at least two complete ice advance/retreat cycles. The occurrence of décollement surfaces, plastically deformed proglacial sediments, and hydrofractures indicate a dynamic, warm-based or polythermal glacier. Abundant outwash sediments, rhythmites with dropstones, and the shift to average CIA values all support a temperate paleoclimate. Deformation structures indicate a NW direction of ice shove that is in agreement with the regional-scale hypothesis that a NNW flowing lobe extended out of Uruguay during the Carboniferous and terminated in the southernmost Paraná Basin. This study demonstrates that late Paleozoic glaciation in this region was more dynamic than previously understood, with high frequency fluctuations in ice marginal positions. [ABSTRACT FROM AUTHOR]

Between 22 and 17 cal ka BP, five large meltwater events from within the Laurentian Channel Ice Stream deposited mud beds meters thick across a large area of the Laurentian Fan and adjacent continental slopes. This study determines the sources of these event beds and relates them to the glaciological evolution of the retreating Laurentian Ice Stream. We analyzed major element and magnetic mineral contents of these event beds and compare them with a new collection of 80 source reference samples from the Gulf of St. Lawrence area. Element ratios suggest a steady compositional change from older to younger outburst event beds, while element-specific offsets from reference sample compositions indicate grain-size and mineral/element partitioning during suspension transport. Their magnetic properties place event beds on the source mixing trend of four reference samples groups, which represent two magnetite-rich sources (Canadian Shield and/or Southern Newfoundland) and two hematite-rich sources (Appalachian red beds). Using a deterministic linear source mixing model based on IRM 100mT , HIRM and Ca%, we find that the earlier two outburst events had higher contributions from granitic and calcareous sources than the later three events. Combining materials, timing and scenarios of the outburst events with ice-sheet retreat and ice-stream dynamics, we argue that the subglacial sediment depocenter of the earlier two event beds was located in the lower Laurentian Channel while that of the later three events was upstream from Cabot Strait. • Event bed sediments unmixed from new Gulf of St. Lawrence reference sample data. • Hematite, magnetite and calcite are most indicative tracer minerals for provenance. • Quantify contributions from surrounding red-bed, granite and carbonate rock provinces. • Demonstrate element partitioning by subglacial outwash and hyperpycnal plume transport. • Sediments premixed in subglacial depocenters above outer and inner Laurentian Moraines. [ABSTRACT FROM AUTHOR]

Turbidite strata are common along faulted margins of half-graben lacustrine basins, but complex lobe evolution may cause significant variability and uncertainty in the spatial distribution of turbidite sand bodies. This study integrates core samples, seismic and well log data from the Dongying Depression lacustrine basin in East China, and uses these data as inputs to a reduced-complexity stratigraphic forward model of turbidite fan lobe evolution. Data-unconstrained sensitivity analysis is used to investigate sensitivity of fan-lobe spatial distribution to fault-related subsidence rate, basin-margin slope, sediment input volume, and sediment input volume oscillation period. A data-constrained multiple-scenario approach then varied parameters within defined uncertainty ranges to generate a series of best-fit models to predict optimal reservoir presence locations. Results indicate that syn-rift segmentation of the Shengbei fault leads to spatial and temporal variation of fault-related subsidence in the hanging wall basin. External controls exert systematic impact on the spatial distribution of both smaller-scale flow beds and larger-scale fans on basin floor. Higher rates of fault-related subsidence and smaller sediment input volume produce more laterally confined fan lobe distribution. Higher basin-margin slope gradient produces more laterally clustered turbidites, but does not change fan lobe location, indicating break of slope is a more significant control on fan location. Multiple scenario reservoir presence probability maps suggest that bypass-dominated middle and inner fan areas, and smaller lengths of retrogradation-dominated feeder channels are most promising reservoir locations. • Syn-rift fault segmentation lead to spatial-temporal variation of fault-related subsidence in the hanging wall basin. • External controls impact the spatial distribution of both smaller-scale flow beds and larger-scale fans on basin floor. • Some middle-to-inner fan areas and sections of the lobe feeder channels have best reservoir presence probability. [ABSTRACT FROM AUTHOR]

Channel-feeding fan deltas without any conglomerates have recently been discovered on the steep slope in the Albert basin at the northern end of the west branch of the East African Rift. However, the new deposition system's mechanics and patterns are unknown. To reveal the sedimentary process of the distinctive fan delta, we integrate forward stratigraphic modeling (FSM) technology with interpretations of the core, well logs, and 3D seismic data. Firstly, a reference FSM model is constructed to describe the evolution of the fan delta, taking into account initial bathymetry, source supply, lake level, and fluvial discharge as independent variables. Then, the Orthogonal Experimental Design (OED) is employed based on the uncertainty analysis of each independent factor to generate FSM multi-realizations for formation thickness and Net-to-Gross. Sensitivity analysis of Multi-FSM realizations reveal that source supply is the most influential variable affecting formation thickness and texture. Combined with the tectonic evolution of Albert Basin, the formation dip during the deposition period is much smaller than present. Multiple incised channels were formed in the provenance area, which became the primary source system of the fan delta, facilitating the sediments' transportation over a certain distance to produce well-developed cross-bedding sandstone. The channel-feeding fan delta has a narrower plain and wider front, and the principal sand body is high-quality distributary channel. The discovery of the channel-feeding fan delta without any gravel formed on the steep slope of the rift basin enriches the theory of deposition in rift basins. In addition, the application of FSM technology helps to improve the quantification of sedimentary processes. • Channel-feeding fan delta without any conglomerate deposited in the south steep zone of Albert Rift. • Source supply, initial bathymetry, transportation, and eustasy were used for the experimental design of FSM. • Sensitivity analysis indicates that sediment supply significantly influences the stratigraphic thickness and texture. • The channels-feeding fan delta has a limited fan delta plain and wider front with medium-coarse sands but few gravels. [ABSTRACT FROM AUTHOR]

The seismic architecture of a tuff-dominated volcanic complex and the associated carbonate systems in the Upper Cretaceous Taylor Group (Anacacho Limestone) Elaine field in South Texas was examined using a three-dimensional seismic dataset. The investigation demonstrates that the combination of traditional seismic lithofacies analysis and seismic sedimentology allows the visualization and interpretation of volcanic elements and penecontemporaneous carbonate lithofacies at the scale of tens of meters. A wireline-log based, rock-physics model was analyzed and calibrated using core samples, which link volcanic and carbonate lithofacies to 90°-phase seismic amplitude events. Seismic-velocity effects permit the identification of subtle volcanic lithofacies changes such as low-velocity tuff bodies or high-velocity basalt intrusions. Also, frequency fusion expands seismic visualization of thick lithofacies bodies (e.g., basaltic dykes) to the 100-m range and seismic facies analysis helps understand interrelationships between the components in and adjacent to the volcanic body. Horizontal seismic slices reveal seismic geomorphology at multiple stages of volcanic activity. This investigation reveals three major seismic facies systems (1) a magma-feeder (i.e., plumbing) intrusive system beneath the volcano, including deep faults, dykes and sills, and remnant radial/concentric fault systems; (2) a large (4000–5000 m diameter) volcanic complex consisting of a deep crater (300-m negative feature below the paleo-sea floor), a large mound (200-m positive feature above the paleo-sea floor), multiple secondary craters filled predominantly with tuffs and less common lava flows; and (3) penecontemporaneous carbonate systems including fringing and mound-top shoals and reefs, lagoon and debris fan aprons at the base of the volcanic mounds. The fringing and mound top carbonate systems were probably in water depths less than 20 m whereas for the fan-apron carbonates, water depths are estimated to be about 140–200 m. These carbonate bodies can form hydrocarbon reservoirs. • A seismic-sedimentologic study of subsurface volcanic architecture in improved resolution. • Interpretation of magma feeder, volcanic complex, and associated carbonate system. • Recognition of a new tuff-cone type volcanic model. • New workflow tailored for volcanic reservoir prediction by integrating 3D-seismic data, wireline logs, and cores. [ABSTRACT FROM AUTHOR]

The characteristics and evolution of different types of channel-complex sets (CCSs) have long attracted attention from both academia and the oil industry. 3D seismic data from the world's largest submarine fan in the Bay of Bengal allow the exploration of morphology, architecture, and evolution of a Pleistocene submarine channel system from inception to abandonment. Four types of architectural elements are recognized, including feeder and distributary channel-complex set (CCS), levees, bend cutoffs, and incised and unincised crevasse splays. Three types of CCSs are recognized: (1) erosional non-leveed CCSs with the lowest values of channel width (W), thickness (T), and cross-sectional area (C a) (mean values of W = 153 m, T = 20 m, and C a = 2613 m2); (2) graded CCSs with the highest values of W , T and C a (mean values of W = 745 m, T = 89 m, and C a = 49183 m2); (3) aggradational leveed CCSs with intermediate values of W , T and C a (mean values of W = 476 m, T = 56 m, and C a = 21968 m2). Graded CCSs and aggradational leveed CCSs have overbank levees, crevasse splays and bend cutoffs, whereas erosional non-leveed CCSs lack these features. Such architectural difference in overbank deposits suggests a channel evolution pattern of initial incision (erosional non-leveed CCSs) and then aggradation (graded and aggradational leveed CCSs), resulting in a pattern of incision-to-aggradation channel evolution. An increase-then-decrease in channel morphometrics (represented by W , T , and C a) from erosional non-leveed CCSs with the lowest mean values of W , T , and C a , to graded CCSs with the highest mean values of W , T , and C a , and finally to aggradational leveed CCSs with the intermediate mean values of W , T , and C a suggest that the incision-to-aggradation channel evolution is related to waxing-then-waning energy cyclicity. Submarine channel turbidity flows during the waxing energy phase became progressively more energetic and increasingly more erosional, producing erosional non-leveed CCSs. Instead, submarine channel turbidity flows during the waning energy phase were more diluted and increasingly more depositional, thereby producing aggradational leveed CCSs. The phase of peak environmental energy was most likely accompanied by most energetic turbidity currents, resulting in graded CCSs. Results and observations from the current study contribute to a better understanding of architectural complexity and evolution of submarine channels. • Channel morphometrics increase-then-decrease from erosional CCSs, to graded CCSs, and finally to aggradational CCSs. • Graded and aggradational CCSs have overbank levees, crevasse splays and bend cutoffs, but erosional CCSs don't. • Channel evolution from erosion, to gradation, finally to aggradation was related to a waxing-then-waning energy cyclicity. [ABSTRACT FROM AUTHOR]

Submarine fans are ubiquitous in modern deep-water environments. Such systems reported in the literature are largely fed by shelf-indented canyons receiving ample fluvial or longshore drift sediment inputs, whereas those nourished by slope-confined canyons far away from terrigenous sediment sources remain poorly understood. Herein, we report such a system, the Yitong submarine canyons – fan apron system (YCFS), from the northern South China Sea. This system was studied using multibeam bathymetric and two-dimensional multichannel seismic data, combined with geological constraints from nearby International Ocean Discovery Program drilling sites. YCFS consists of approximately 12 submarine canyons confined in the lower continental slope of >1200 m water depth, which feed a fan apron in the connecting abyssal plain. The canyons are erosion-dominated, as evidenced by their V-shaped cross-sections with up to 708 m deep incisions. Canyon infillings comprise mass transport deposits and turbidites, and interfluves exhibit features such as landslides, creep-typed sediment waves, and gullies, indicating the canyons and interfluves are dominated by mass transport and turbidity-current processes. The fan apron is generally depositional, in which channels and channel-levee complexes, turbidite lobes, and mass transport deposits comprise the main depositional elements. In the canyon-to-fan transitions, supercritical turbidity current features and bedforms, including plunge pools and connected sediment mounds, cyclic steps, and antidunes, are developed, which are linked to the deceleration and hydraulic-jump effects of the high-velocity turbidity currents shedding off the canyons. Seismic stratigraphic analysis revealed that YCFS was initiated in Late Miocene. The formation and maintenance of YCFS are linked to the long-term existence of an upslope margin-parallel basement high. The latter could have maintained a steep slope condition (up to 6.5°) that favors the development of canyons and supercritical turbidity currents. Because of the blocking effect of the basement high , YCFS receives limited supply of the shallow-water sediments. • A deep-sea fan apron fed by slope-confined canyons lacks ample land-based supply. • Developed supercritical-flow bedforms indicate high-energy fan apron environments. • Tectonism plays a critical role in the development of the system. [ABSTRACT FROM AUTHOR]

Glaciation during the Late Paleozoic Ice Age climatic interval (~370–260 Ma) was likely dynamic; consisting of numerous ice centers that grew and shrank asynchronously through time. Improvements in understanding of the spatial and temporal depositional complexity of glaciomarine sedimentary systems have shown that in order to characterize the conditions of Late Paleozoic glaciation, glaciogenic depositional systems and their stratigraphy must fundamentally be understood at the local level. To that end, this study reexamines the physical sedimentology and sequence stratigraphy of the type-section of the Permo-Carboniferous, glaciomarine Wynyard Formation (Wynyard Tillite) of the Tasmanian Basin by describing a 415 m thick interval of the formation, beginning at its basal erosional unconformity with the Proterozoic Burnie (Oonah) Formation. The glaciogenic nature of the Wynyard Formation stratigraphy is indicated by the characteristics of clasts throughout the succession (striated, faceted, angular, and variable lithologies and grain sizes). Three glacial depositional environments were interpreted: a grounding zone wedge deposited in an ice-contact setting, glacier-proximal portion of a grounding line fan and/or morainal bank, and cyclopelites deposited in a glacier-intermediate to glacier-distal setting. Mass transport and turbidite deposits are common throughout all facies associations, as is soft sediment deformation likely caused by slumping. Several boulder pavements occur throughout the succession, indicating periodic glacier grounding. Together, these facies associations indicate that this Wynyard Fm succession is composed of glaciogenic sediments that were deposited in sub-aqueous, marine, predominantly proglacial environments. The sequence stratigraphic analysis indicates that this entire succession of the Wynyard Fm was likely deposited during the single retreat phase of the "Wynyard Glacier", with one notable readvance over the area. The interpretations made by this work enhance the understanding of glaciation of the Tasmanian Basin during the LPIA through facies analyses and a sequence stratigraphic approach, which allowed for detailed subdivision of lithologies that enabled inferences regarding the type, timing, and extent of the "Wynyard glacier". This Wynyard Fm succession was likely deposited during a single glacier retreat with some minor readvances that may have occurred on the order of decades to years. Additionally, the glacier's grounding line was likely never more than a few kilometers upglacier (south) of this location during deposition. These findings are significant, because the massive diamictites that comprise this succession had previously been considered homogenous and therefore resisted detailed interpretations. Constraining the often-complex depositional histories of glaciogenic strata in similar fashions across the Tasmanian Basin allows us to better understand how these glaciogenic deposits fit into the global climate system of the Late Paleozoic Ice Age. [ABSTRACT FROM AUTHOR]

Deep-water turbidite channels are conduits for transporting terrigenous clastic sediments into the ocean, and channel deposits can also act as high-quality hydrocarbon reservoirs. In this study, based on high-resolution 3D seismic data and logging-while-drilling data, four Pleistocene turbidite channels are identified and characterized in the deep-water area. These deep-water channels are sinuous with V- or U-shaped on the seismic profiles, and their evolutionary history can be divided into Unit 1 (Erosion-dominated stage), Unit 2 (Erosion-Deposition stage), Unit 3 (Erosion-Deposition stage), and Unit 3 (MTDs-dominated stage). The internal fillings of these channels are almost basal lags with high-amplitude reflections at the bottom, pelagic sediments with low-amplitude reflections, and mass transport deposits with translucent/transparent seismic facies. Since sand-rich sediments dominate the deep-water channel-levee systems in Unit 3 in the study area, they could act as shallow gas reservoirs and facilitate the accumulation of gas hydrates. By analyzing the source-to-sink systems around the basin, the source of the sediments within the deep-water channels is discussed, which are mainly from the Truong Son Belt. Floods, sea level fluctuations, and earthquakes are the most likely triggering mechanisms of turbidity currents in the Qiongdongnan Basin. This study provides new insights into the Quaternary deep-water sedimentary process, gas hydrate exploration, and source-to-sink systems in the northwestern South China Sea. • Highly sinuous sand-rich turbidity channels are characterized in deep-water area of the Qiongdongnan Basin. • Impacts of the deep-water turbidite channels on the accumulation of shallow gas and gas hydrates are documented. • The source and formation mechanism of the deep-water turbidite channels are illustrated. [ABSTRACT FROM AUTHOR]