Gravity Flow Research Articles

Fault control on sedimentation in the southern gentle slope of the Dongying Sag, Bohai Bay Basin

Located in eastern China, the Dongying Sag is characterized as a prototypical rift basin with intricate fault systems. While research efforts have traditionally honed in on the geometry and kinematics of the northern steep slope zone, the structural characteristic of the southern gentle slope zone (SGS) have received comparably less attention, with a notable gap in the understanding of the fault's geometry and kinematics. The sedimentary facies distribution of the rift basin is unequivocally linked to structural activity, but previous studies have treated sedimentary facies and structural characteristics in isolation, leading to an unclear comprehension of the factors influencing sedimentary facies distribution. This study leverages 3D seismic data encompassing 650 km2 along with 20 well logs, directing focus on the key fault zones within the SGS (i.e. Chenguanzhuang (CGZ) and Liangjialou (LJL) fault zone). Using methodologies such as seismic-well integration, planar attribute extraction, and throw-stripping, the research studies the geometric and kinematic characteristic of these fault zones, scrutinizes their activity features, and elucidates the interplay between structural and sedimentary processes in both temporal and spatial dimensions. The results show that (1) the CGZ fault zone is characterized by an array of east-west oriented, en-echelon faults, which nucleated during the nascent phases of rifting (Es4). Within the fault zone, the F1 fault exhibits the greatest strike extension, which can be further segmented into three distinct sections: F1-1, F1-2, and F1-3. These segments have undergone a kinematic evolutionary process of “separation-connection-extension” during the Es. Concurrently, the SGS is subject to a supply of sources from an east-west orientation, leading to the development of a delta-gravity flow sedimentary system within the hanging wall of the CGZ fault zone. (2) Conversely, the LJL fault zone exhibits a broom-like , comprising a series of NEE-oriented faults. The predominant faults (i.e. F10, F11, and F13) nucleated during the late rifting phase (Es3u). Concurrent with the Es3u interval, the northern part of the study area developed shallow-water delta within the hanging wall of the LJL fault zone. (3) During the Es3m period, the expansion index of the CGZ fault zone attained its zenith, this has facilitated the formation of gravity flow deposits arising from slumping at the delta front. Subsequently, fault activity within the study area experienced an overall decline, the gentle paleo-topography promotes a large-scale shallow water delta developed in the Es3u. The decreasing activity of the CGZ fault zone and the increasing activity of the LJL fault zone in Es3u drove the depocenter shifting towards the NW.

Provenance of mixed volcaniclastic-carbonaticlastic gravity-flow deposits: a case study from the Cretaceous of the southern Central Alborz (Iran)

ABSTRACT Understanding the petrographic and geochemical characteristics of different tectonic settings is essential to improving traditional methods of identifying the provenance of palaeo-sedimentary environments. This research focuses on the K2b unit, which consists of mixed carbonate and volcanic lithic sandstones located in Iran with the age of the Turonian-Early Campanian period. Five sedimentary lithotypes with distinct petrographic and geochemical signatures were identified in the Turonian/Lower Campanian K2b unit, which consists of coarse-grained fan-delta strata. Carbonate and volcanic lithic fragments are the most characteristic components of mostly quartzo-lithic to felspatho-litho-quartzose sandstone layers, documenting a unidirectional paleocurrent pattern with the north-eastward direction. The original composition has undergone diagenesis, resulting in the precipitation of authigenic carbonates and depleting Rare Earth Elements (REE) except for Eu, which shows a positive anomaly. The K2b fan delta was situated on the margin of the proto-south Caspian back-arc basin, and the sediments were sourced from the undissected magmatic arc. The gravity flow deposits in the K2b unit were likely triggered by tectonic activity in the catchment area of the fan delta, leading to uplift and formation of relief associated with the regional Mosha Fault and, on a larger palaeogeographic scale, with subduction of the Arabian plate beneath the Iranian plate during Turonian-Early Campanian.

Random and time-persistent depositional processes in turbidite successions: an example from the marine deep-water Aoshima Formation (Neogene, Kyushu Island, southwest Japan)

ABSTRACT The deposits of flood- and earthquake-derived subaqueous sediment gravity flows represent a significant fraction of lacustrine and deep-sea sedimentary successions, thus providing a valuable record of such natural disasters. The magnitude of these events and the thickness of the associated deposits are considered to follow a lognormal or power-law frequency distribution, whilst that of time intervals between subsequent events appear to be best approximated by a Poisson model, indicative of a random, time-independent phenomenon. However, the debate on whether the sedimentary record of these natural disasters is governed by randomness alone or whether there is some underlying stratigraphic ordering is still unsettled and requires detailed time-series analysis. This study consists of a time-series analysis of mudstone- and sandstone-dominated turbidite successions offshore a fan-delta system in the Neogene Aoshima Formation that belongs to the sedimentary fill of the forearc basin of southwest Japan. The formation consists of a monotonous alternation of very fine- to medium-grained sandstones capped by hemipelagic mudstones and, more rarely, by turbidite mudstones. The results show that the autocorrelation function of the time series suggests quasi-periodic variability in the upper sandstone-dominated part, whereas the lower mudstone-dominated part shows a white-noise-like pattern. Rescaled range analysis shows that the number of events per unit time in the lower part is characterized by a random time series, such as Brownian noise with a Hurst exponent of 0.5. In contrast, the thickness of event beds of the lower part and the thickness and the number of events of the upper part are persistent time series with a Hurst exponent > 0.5. These results suggest that the number of turbidite depositional events in the mudstone-dominated part indicates random timing, whereas its thickness time series and the sandstone-dominant part are not governed by simple stochastic processes but are affected by sea-level changes, sediment transport dynamics, and other factors such as, for example, seafloor topography.

Reservoir Quality Under the Control of Gravity Flows in the C7 Member of Yanchang Formation in the Jinghe Oilfield, Ordos Basin, China

The late Triassic sandstone reservoir in the C7 member of the Jinghe oilfield southern Ordos basin is a typical deep-water gravity flow tight oil reservoir. Sedimentary microfacies, physical properties, and petrographic analysis were being examined for quality determination. Pore structure and physical properties data together combined with, thin sections, and scanning electron microscope and core images were used to identify factors controlling reservoir physical properties. The depositional system under debates of different gravity flows including debris flow, seismite slumping, and turbidity flows. Among which sandy debris flow facies shows a better distribution of porosity and permeability followed by seismite-slump, where turbidity facies are the poorest. The petrophysical analysis shows that the study oil interval is a typical tight sandstone reservoir with an average porosity of 9% and permeability average being 0.025mD. The rock classification criteria of the C7 sandstone reveal the sub-categories of lithic feldspar sandstone and feldspar lithic sandstone. Average quartz sandstone contents of 48.25%, average feldspar sandstone content being 25%, and lithic fragments content of 29%. The formation lithology comprises mostly fine-grained sandstone and small pore size, which disclose that the porosity-permeability distribution increases proportional to the average and median pore throat radius, and decreases with average and median pressure. The microfacies distribution shows that the depositional facies controlled physical properties. The sandstone primary pores are affected by the mineral composition of quartz, feldspar, illite, smectite, kaolinite, calcite, and dolomite. Features such as dissolved pores and intergranular pore filling by feldspar, silky-like aggregates of illite-smectite intergranular pore filling and most diagenetic minerals influenced the sandstone pores beside the compaction.

The role of ice-sheet dynamics in the Miocene-Pliocene depositional systems of the Ross Sea, Antarctica

The dynamics of the Antarctic ice sheet (AIS) have profound implications for the evolution of the Antarctic continental margin, global ocean currents, and climate changes. Marine sediments from the Antarctic continental margins recorded the history of the advance and retreat of the AIS. In this study, we present an integrated analysis of the sedimentary characteristics of the Early Miocene to Late Miocene of the Ross Sea by using 2D seismic reflection data and cores from International Ocean Discovery Program (IODP) Expedition 374 Sites U1521, U1522, and U1524. The characteristics of the seismic facies and sediments show that the expansion and grounding of the ice sheets across the continental shelf significantly influenced the depositional processes, leading to increased glacial erosion, the formation of prograding wedges, mass transport deposits (MTDs), and mixed (turbidite-contourite) depositional systems since the Early Miocene. The seaward migration of the continental shelf edge and the steepening of the continental slope were mainly influenced by the glaciation of extreme expansion of the AIS. Marked increases in the prograding wedge and MTD are associated with extensive sediment reworking and deposition at the grounding zones and along the continental slope as a result of ice sheet expansion. The development of the mixed (turbidite-contourite) depositional systems was the result of extensive sediment reworking and deposition by gravity flows and bottom currents on the continental slope and the rise. This research provides new insights into the complexity of the ice sheet and the sensibility of marginal sediments in responding to the past climate changes in Antarctica.

Sedimentary characteristics of hybrid event beds in deep-lacustrine basins and their impact on reservoir quality: Examples from the Bohai Bay Basin, Eastern China

Hybrid event beds (HEBs) form important components of subaqueous sediment gravity flow models in deep-lacustrine sedimentary basins, largely due to their clay-rich nature meaning that they often form non-reservoir and/or baffles/barriers to fluid flow in the subsurface. Using examples from a typical deep-lacustrine basin, this study documents the sedimentary characteristics and distribution of HEBs and explores their effect on reservoir properties. To achieve this, a suite of drill cores and wireline data through a range of debrites, concentrated flow deposits, and turbidites are analyzed from Paleogene in the Bohai Bay Basin, China. The superposition and convergence of gravity flow deposits resulted in a complex spatial and temporal distribution and evolution of the HEBs in the study area. The majority of identified HEB types are interpreted to be associated with lobe deposition. However, slumping-induced HEBs are interpreted to be restricted to the proximal slump areas. Slump HEBs are interpreted to have formed through slumping and associated generation of sediment gravity flows, where HEBs formed through flow transformation of slumps into high-concentration flows (debris flows) and/or high-density turbidity currents in down-slope areas. Debris flow HEBs are interpreted to be formed by particle rearrangement through vertical settling during flow transformation within the subaqueous fans. The effects of relative buoyancy in debris flows, rearrangement of debris flow particles, muddy substrate erosion by turbidity currents, and slumping upon HEB development are discussed. The average porosity and permeability observed within reservoir intervals formed by gravity flow deposits are 17.8 % (ranging from 2 % to 25 %) and 126 mD (ranging from 3 mD to 816 mD), respectively. HEBs within the studied reservoir interval display low-porosity (<15 % on average) and low-permeability (<10 mD on average) values. The occurrence of HEBs within a reservoir increases the variation coefficient of permeability, quantity, and thickness of the interlayers and presents a significant heterogeneity. The results of this study are important to consider in the context of constructing reservoir models in deep-lacustrine reservoirs of the Bohai Bay Basin, and which can be applied to other lacustrine gravity flow deposits in sedimentary basins worldwide.

Pockmarks Offshore Big Sur, California Provide Evidence for Recurrent, Regional, and Unconfined Sediment Gravity Flows

AbstractRecent surface ship multibeam surveys of the Sur Pockmark Field, offshore Central California, reveal &gt;5,000 pockmarks in an area that is slated to host a wind farm, between 500‐ and 1,500‐m water depth. Extensive fieldwork was conducted to characterize the seafloor environment and its recent geologic history, including visual observations with remotely operated vehicles, sediment core sampling, and high‐resolution, near‐bottom Chirp and multibeam surveys collected with autonomous underwater vehicles to capture the morphology and stratigraphy of the pockmarks. No evidence of high methane concentrations in sediments, chemosynthetic biological communities, or methane‐derived diagenetic byproducts was found. Chirp data and sediment cores showed alternating layers of slowly accumulating hemipelagic drapes interrupted by more reflective turbidite horizons that extend throughout the pockmark field and beyond. Chirp data showed multiple episodes of lateral migration over time in some of the pockmarks in association with erosion and infilling events. Laterally continuous turbidite horizons that overlay erosional surfaces indicated that pockmark migration occurred synchronously in multiple pockmarks separated by tens of kilometers. These shifts are presumed to be the result of asymmetrical erosion of the pockmark flanks caused by passing sediment gravity flows. While some pockmarks occur in chains, most are not clustered or randomly spaced but are regularly dispersed within the pockmark field. We hypothesize that intermittent, unconfined sediment gravity flows occurring over at least the last 280,000 years are the source of the regionally continuous turbidite deposits and the mechanism that maintained the regularly dispersed pockmarks.

Subduction history of the Paleo-Asian oceanic slab along the northern margin of the North China Craton: A case study of zircons and cherts from central Jilin Province, NE China

This paper presents U-Pb ages and Hf isotope data for detrital zircons and whole-rock geochemical data for siliceous-clastic sedimentary rocks of the Shitoukoumen Formation, central Jilin Province, NE China. The new data combined with published data for the northern North China Craton enable us to constrain the temporal changes in crustal thickness along the Solonker−Xar Moron−Changchun−Yanji suture belt (SXCYB). The Shitoukoumen Formation contains ophiolitic lenses, radiolarian-bearing cherts, and volcanic-sedimentary units of various ages. A radiolarian-bearing volcanic-sedimentary unit exhibits a Bouma sequence, in which detrital zircons from a rhyolitic tuff and siliceous-clastic sedimentary rocks yielded youngest ages of 278−273 Ma, which constrain the depositional age of the unit. The geochemical compositions of the cherts suggest the pelagic deposits contain some continent-derived clastic material and may be near-trench gravity flow deposits. The dominantly depleted zircon εHf(t) values of the sedimentary rocks in the Shitoukoumen Formation record extensive crustal growth during the Paleozoic. The variations in the crustal thicknesses during the Paleozoic to early Mesozoic record a tectonic transition from subduction initiation, mature continental arc, and finally to Paleo-Asian ocean closure. The thickest crust (∼58 km) at ca. 245 Ma might have been related to an orogenic peak during the final closure of the Paleo-Asian Ocean along the SXCYB.

Source rock and climate model for the Cretaceous Jiufotang Formation, Kazuo Basin, China: Geochemistry and petrography

The Lower Cretaceous Jiufotang Formation, situated in western Liaoning Province, China, has attracted attention for abundant Jehol Biota fossils and the potential to improve understanding of the relationships among climate change, evolution of terrigenous organisms, and organic matter (OM) enrichment in lake systems during the Early Cretaceous. Based on organic petrology and biomarker analyses, this study investigated the depositional environment, OM sources, and enrichment mechanism of Jiufotang mudstone in the Kazuo Basin. Maceral composition shows that the OM source of Jiufotang mudstone shifted from mainly aquatic to terrigenous, and biomarkers such as abundant diterpenoids and retene indicate that terrigenous higher plants were mainly conifers during deposition of the Jiufotang Formation. Pr/Ph ratios (0.07–0.65) show that the studied section was deposited in anoxic bottom water that may be necessary for OM enrichment in lake systems. Gravity flows were accompanied by input of many clastic minerals and oxygenation of bottom waters, which is unfavorable for OM enrichment. Therefore, the best OM enrichment model for lake systems includes anoxic bottom water, stable water column stratification, low sedimentation rates, and high phytoplankton contributions. The climate changed from relatively dry to humid, which drove changes in the OM enrichment model in the lake. More importantly, the climate and terrigenous plant information obtained by biomarkers is useful to reconstruct the ecological environment of the Jehol Biota.

Submarine landslides and tsunami genesis in Sagami Bay, Japan, caused by the 1923 Great Kanto earthquake

The 1923 Great Kanto earthquake occurred on September 1, in Japan, and caused severe damage mainly in the Kanto region. Tsunamis were observed over wide regions from the east coast of the Izu Peninsula to the west coast of the Boso Peninsula, and particularly, the damage in Atami was devastating. Many earthquake fault models including those of Kanamori (1971) and Ando (1971) were proposed based on the records of land deformation. However, such fault models cannot sufficiently explain the tsunami elevation and its initial sea-level motion on the coasts. Hence, the detailed mechanisms remain elusive. This study examines the possibility that a leading mechanism of the tsunami in the 1923 Great Kanto earthquake was a large-scale submarine landslide that occurred at Sagami Bay and at the mouth of Tokyo Bay based on the records of depth data measured by the Imperial Japanese Navy (1924) before and after the earthquake. We first show that the tsunami calculated by each fault model was inconsistent with the waveform at Yokosuka, the coastal tsunami elevations, and initial sea-level motion. Then, based on statistical analysis of the depth changes at the 1923 Great Kanto earthquake, we found that the seafloor bathymetric changes represented large-scale submarine landslides that may correspond to long-runout submarine liquefied sediment flows. The seafloor gradient over a 40 km flow-out distance was equal to or less than 0.4∘\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^\\circ$$\\end{document}. Through the identification of the submarine landslide source by tsunami backpropagation analysis and utilizing an analytical solution of a high-density gravity flow and a sensitivity analysis, we conducted a range of numerical simulations of the 1923 Great Kanto earthquake tsunamis using a fault model and a submarine landslide tsunami source model due to a high-density liquefied gravity flow. The results quantitatively accounted for the discrepancy between the observed tsunami records with maximum tsunami elevations over 12 m and the fault-model–based simulations with maximum tsunami elevations of 2 to 5 m and explained consistently the maximum tsunami elevation distributions as well as the time-series tsunami waveforms. These results may thus facilitate and deepen our understanding of the earthquake-induced submarine landslide tsunami risk as cascading multi-geohazards.

Mixed siliciclastic-carbonate-tuffaceous sedimentation in a rift lacustrine basin: A case study of the Lower Cretaceous Jiufotang Formation in the Luxi sag, Songliao basin

The Lower Cretaceous Jiufotang Formation lacustrine successions in the rift Luxi sag, Songliao Basin are characterized by mixed siliciclastic-carbonate-tuffaceous and organic-rich deposits. Ten facies were recognized and were formed in fan delta, delta, littoral-sublittoral lacustrine and deep lacustrine environments. A depositional sequence characterized by significant changes in facies and lake regime has been defined, and is divided into lowstand systems tract (LST), transgressive systems tract (TST), and highstand systems tract (HST) that are separated by sequence boundaries, initial flooding surfaces, and maximum flooding surfaces, respectively. During the LST, the delta and fan delta deposits covered the marginal area and extended into littoral-sublittoral lacustrine and deep lacustrine environments, respectively. During the TST, the areas of delta and fan delta decreased and lake areas increased, and the carbonate-dominated shoals and mixed siliciclastic-carbonate shorelines occupied the edge of the Majiapu highland belt. During the HST, the lake areas further expanded, and the fan delta deposits extended into deep lacustrine environments and formed deposits of underflows and turbidites. A depositional model in the rift lacustrine Luxi sag is proposed, incorporating the effects of tectonics and sediment supply, climate and carbonate production, hydrodynamic conditions, and lake-level fluctuations. During the LST, the active tectonic movement, high input of siliciclastic sediments, and subaerial volcanic eruptions resulted in the wide distribution of mixed siliciclastic-tuffaceous sedimentation. During the TST, the brackish lake water controlled by periodic dry and hot climate facilitated the carbonate deposition in shallow water, and tractional currents onto the lake shore carried sediments to form the mixed siliciclastic-carbonate-tuffaceous facies. During the HST, more humid climate and increased runoff allowed formation of widely distributed, mostly oil shale-rich deposits, and the gravity flows carried the sediments into the deeper part of basin to form the mixed siliciclastic-carbonate-tuffaceous facies. The depositional model of mixed deposits in this rift lacustrine basin has been proposed here in order to encourage comparison with other similar basins.

A Robust and Efficient Method to Purify DNA-Scaffolded Nanostructures by Gravity-Driven Size Exclusion Chromatography.

In recent decades, nucleic acid self-assemblies have emerged as popular nanomaterials due to their programmable and robust assembly, prescribed geometry, and versatile functionality. However, it remains a challenge to purify large quantities of DNA nanostructures or DNA-templated nanocomplexes for various applications. Commonly used purification methods are either limited by a small scale or incompatible with functionalized structures. To address this unmet need, we present a robust and scalable method of purifying DNA nanostructures by Sepharose resin-based size exclusion. The resin column can be manually packed in-house with reusability. The separation is driven by a low-pressure gravity flow in which large DNA nanostructures are eluted first followed by smaller impurities of ssDNA and proteins. We demonstrated the efficiency of the method for purifying DNA origami assemblies and protein-immobilized DNA nanostructures. Compared to routine agarose gel electrophoresis that yields 1 μg or less of purified products, this method can purify ∼100-1000 μg of DNA nanostructures in less than 30 min, with the overall collection yield of 50-70% of crude preparation mixture. The purified nanocomplexes showed more precise activity in evaluating enzyme functions and antibody-triggered activation of complement protein reactions.

Lithological controls on the timing of strath terrace staircase formation in a collisional mountain belt

AbstractIn mountain belts, strath terrace staircases serve as markers for deriving river incision rates and erosional patterns. Distinguishing between terrace patterns influenced by external perturbations like changes in climate and tectonics and those driven by internal dynamics including feedbacks between topography, erosion and sediment transport remains challenging. We demonstrate that in a collisional mountain belt, lithology can act as a first‐order control on the spatial and temporal scales of strath terrace formation. Here, we investigate the role of lithology in modulating internal dynamics and the formation of strath terraces in the Mgoun River catchment of the High Atlas in Morocco, a region characterised by constant low‐rate rock uplift, a cyclical cool‐warm/arid‐humid Quaternary climate history and contrasting bedrock lithologies. By collecting (1) modern river and terrace clast data, (2) bedrock strath and strath‐top sediment elevations of four terrace levels, (3) terrace sedimentology and (4) integration with published terrace chronology, we found a dominance of local sediment input from hillslopes, mostly from recycled bedrock conglomerates. Additionally, we found valley width, controlled by the stratigraphic and structural configuration of lithological erodibility, significantly impacts sediment connectivity. The isolation between valleys with varying widths results in varied timescales of river channel response to hillslope coupling, with hillslope‐derived stochastic sediment gravity flows preserved in fluvial terraces in some river reaches and not in others. Furthermore, asynchronous terrace formation and abandonment ages result from the low longitudinal river connectivity between multiple valleys formed in erodible rock separated by gorges in high‐strength rock. These gorges limit knickpoint migration rates, inhibiting the ability of terraces formed in one valley to spread through the catchment. These findings can inform future research distinguishing between autogenic and external signals in erosional landscapes and help carefully derive river incision rates and climate insights from terraces.

The late Quaternary glacial depositional environment at Filey Bay, eastern England: Accretionary mechanisms for thick sequences of tills and stratified diamictons

Construction of the Holderness/Flamborough Head moraine belt on the East Yorkshire coast, England, records the oscillatory onshore flow of the North Sea Lobe of the British-Irish Ice Sheet from ~25.8 to ~19.7 ka BP, during which time a thick sequence of multiple diamictons and associated stratified sediments were emplaced. The sedimentology of a >40 m thick stratigraphy through the moraine belt at Filey Bay, in combination with local borehole records, is used here to reconstruct the depositional processes associated with glacier ice moving ca., 12 km onshore and damming the mouth of the Vale of Pickering, which resulted in the accumulation of an unusually thick and complex sequence of deposits traditionally classified as the “Filey till”. The base of the sedimentary sequence comprises stratified diamictons, which are interpreted as glacilacustrine deposits emplaced predominantly by sediment gravity flows in an ice-contact ‘mud apron’ on the distal slope of a subaqueous push ridge constructed in the earliest proglacial lake in Filey Bay; a vertical increase in coarse-grained lithofacies records increasing glacier proximity. Glacier overriding of the mud apron is recorded by a stacked sequence of tills that interdigitate with lake sediments inland. A zone of till-lake sediment interdigitation migrated first westward during North Sea Lobe advance and then eastward during its retreat, into and out of Glacial Lake Pickering, respectively. Multiple tills and intra-till stratified beds and lenses at the top of the sequence at Filey represent alternating deforming bed-sliding bed facies (subglacial traction tills and subglacial canal fills) associated with the construction of inset push moraines, constructed by sub-marginal incremental thickening or punctuated aggradation. This depositional scenario addresses the problems arising from genetic classifications of substantial accumulations of glacigenic diamictons as ‘till’ when modern analogues indicate only modest thicknesses of subglacial traction till beneath glaciers. Onshore thickening of glacigenic deposits through subaqueous push moraine construction and mud apron progradation is compatible with glacier surging behaviour, but not necessarily solely diagnostic of a surging North Sea Lobe during the last glaciation.

Erosional and Depositional Features along the Axis of a Canyon in the Northern South China Sea and Their Implications: Insights from High-Resolution AUV-Based Geophysical Data

Autonomous Underwater Vehicle (AUV)-based multibeam bathymetry, sub-bottom profiles, and side-scan sonar images were collected in 2009 and 2010 to map the geomorphic features along the axial zone of a canyon (referred to as C4) within the canyon system developed on the northern slope of the South China Sea. These data significantly improved the spatial resolution of acoustic data, leading to a better understanding of the sedimentary processes within the modern canyon system. The bathymetric data reveal that sections across the canyon axis exhibit either asymmetrical or symmetrical characteristics, which differ from the overall asymmetrical pattern of the entire canyon. This suggests that the overall asymmetrical pattern of the canyon is not primarily due to axial incision. Various morphological elements were identified along the canyon axis, including failure scars, undulating features, knickpoints, flat terraces, furrows, and mass transport deposits (MTDs). Landslides, predominantly located in the upper canyon, were formed after at least 5000 years BP. Between the beginning of the canyon and a water depth of approximately 1300 m, there are alternating flat terraces and knickpoints. The large knickpoints’ low slope gradients are likely formed by the presence of undulating features. The internal configurations of undulating features suggest that they are depositional structures rather than sediment deformation. The formation of small-scale furrows below a depth of 1200 m may be associated with occasional gravity flows down the canyon. It is suggested that the canyon was generally inactive during the Holocene but experienced sporadic processes of sediment erosion, transport, and re-deposition in the axial zone that were triggered by landslide events occasionally in the upper canyon.

LITHO-STRATIGRAPHIC FEATURES OF THE LOWER CRETACEOUS DEPOSITS OF THE SKYBA AND DUKLA-CHORNOGORA NAPPES OF THE UKRAINIAN CARPATHIANS AND PROSPECTS FOR THEIR OIL AND GAS POTENTIAL

Lower Cretaceous sediments are widespread within the Skybа and Dukla-Chornorgora Nappes (Spas and Shypot Formations) over a considerable area. These deposits contain sandstones that can be industrial reservoirs for hydrocarbons. Such sandstones are described both on the surface and identified in deep wells. Thick sandy strata in the middle part of the Spas and Shypot formations formed as deposits of gravity flows at the second level of avalanche sedimentation, at the foot of the continental slope of the northern continental margin of the Tethys Ocean. Their formation is correlated with global regression in Aptian time. Porous sandstones of the Spas formations are present on the surface in the areas of the villages of Tershiv and Busovysko. They sometimes form bundles up to 60 m thick. They are exposed in the Oryv and Berehyv Skybas by deep wells 1-Lugy, 1-Shevchenko, and 4-Maksymivka. During the drilling of the 1-Shevchenko well from a depth of 6,900 meters, a film of oil and gas continuously flowed into the drilling mud. According to the results of industrial and geophysical studies, the section of the Spas formations of the second (lower) scale in the interval of 6,940–7,520 m was recognized as the most promising in terms of oil and gas potential. Two promising objects in the intervals of 7020–7070 and 6945–6985 m were identified, the oil and gas saturation coefficients of which are 65–70%. Similar sandstones are noted in the Hoverla sub-Nappe of the Dukla-Chornogora Nappe along the Balzatul River and its tributaries (Bila Tysa River Basin) as part of the Shypot Formation. Sandstones with an open porosity of 8–12 % were identified in the 1-Hrynyava and 1-Semakiv wells in the deposits of the Shypot Formation of the Skupiv sub-Nappe according to the results of industrial-geophysical research. When testing them in the 1-Semakiv well, from the total interval of 473–569 m, they received inflows of combustible gas and light oil with flow rates of 3,000 m3/day and 2.64 m3/day, respectively. The analyzed materials testify to the prospects of the Spas and Shypot formations in relation to the discovery of industrial accumulations of hydrocarbons.

Analysis of the Possibilities of Energy Recovery from Gravity Flows in Pipelines in a Copper Ore Enrichment Plant

Considering the need to reduce climate change and energy costs, the possibilities of energy recovery have been sought for many years, even if this should involve significant complexity of the technological process. Attempts to recover energy from a flowing medium containing a large amount of a solid phase are rather rare. This is mainly due to unfavorable erosion and sludge phenomena. The aim of this work is to analyze the possibility of recovering energy from gravity flows in the pipelines of a copper ore enrichment plant. The analysis will be carried out for a system operating in a plant in Poland. An energy recovery device will be designed taking into account the flow of a two-phase medium. For this purpose, flow calculations will be performed. The calculation results obtained for the two-phase flow will be verified based on the experimental results presented in the literature. The simulations will make it possible to determine the power of the designed device.

Seismic investigation uncovers formation and spatial distribution of seafloor erosional features on the Changjiang (Yangtze) River subaqueous delta

River deltas face erosional challenges driven by global changes and human activities leading to diminished sediment supply. Despite extensive researches on erosional processes within the Changjiang River subaqueous delta (CRSD), there exists a knowledge gap concerning the comprehensive spatial distribution of erosional features throughout the CRSD. This study addresses this gap by utilizing a substantial dataset of high-resolution chirp data to analyze the characteristics, distributions, and stratigraphic terminations of seafloor erosional features within the CRSD. The results unveil an expansive erosion area spanning approximately 2900 km2, occurring at depths ranging from 10 to 40 m in the modern CRSD. These erosional features manifest as extensive truncations, low-relief scoured seafloor, and cut-and-fill structures, distributed variably across the CRSD. Particularly noteworthy is the identification of an alignment between the suspended sediment front and a 20 m water depth erosional area along the deltaic coast. Erosion in this area is dominated by truncations, extending ∼ 10 km in width, and followed by scoured (several hundred meters wide and ∼ 1–2 m deep on average) seafloor. Slope gradient also influences erosion, with cut-and-fill structures (2 km wide and around 5 m deep) that we attribute to sediment gravity flows are identified on steeper slopes offshore of North Channel. Beyond the 20 m water depth, extensive truncations spanning approximately 20 km wide and lead to outcrops of older strata. The spatial distribution of erosional features, coupled with river outlets and subsurface structure, suggests joint influences from reduced riverine sediments, estuarine engineering, wave actions, and tidal regimes. These findings emphasize the primary impact of sediment discharge reduction and underscore the collective influence of various anthropological and natural factors in shaping the spatial distribution of erosional features across different water depths in the subaqueous delta. Insights from this study contribute to a deep understanding of erosional processes and the ongoing evolution of erosional degradation in deltaic systems worldwide.

Geomorphologic and infilling characteristics of the shelf-incising submarine canyon in the eastern Makran accretionary prism, offshore Pakistan

Seven shelf-incising submarine canyon systems are developed in the Makran accretionary prism, offshore Pakistan. This paper uses multibeam bathymetric data and multichannel seismic profiles to study the geomorphologic and infilling characteristics of E Canyon in the east of accretionary prism. The E Canyon extends nearly north–south from the upper slope to lower slope, the bottom of the canyon is located in 1000 to 3000 m water depth, the main axis extends about 55 km, and the width varies from 5 to 9 km. The E Canyon shows U-shaped concave features in the northern cross-section view and V-shaped concave features in the southern cross-section view. Two continuous erosion pools are developed at the fifth and third ridges of the southern segment, respectively. The steepest sidewall (with slopes of 25.75° and 40.47°) of E Canyon was found near the third ridge. The filling sequence of coarse channel lags, slump debris flows, stacked channel sands and mass transported deposits and turbidite deposits from bottom to top is developed in the northern segment of the canyon. Strong erosion is developed in the southern part of the canyon and there is no sedimentation inside. On the abyssal plain, the continuation of the E Canyon is clearly erosive. Our preliminary analysis shows that the factors controlling the evolution of E Canyon may include sediment gravity flow, tectonic activity, sea-level change, climate and onshore rivers activity. The correlation between evolution of E Canyon and gas hydrates was explored, and it is believed that the erosion of E Canyon plays a destructive role in hydrate accumulation. At the same time, the destruction of hydrate-bearing layer induces the escape and leakage of hydrocarbon-bearing fluid, leading to the development of pockmark on the sidewalls of E Canyon. And the evolution model of gas hydrate accumulation in the development area of E Canyon was established.

Evidence for long-term efficacy of a membrane filtration device in rural villages in Ghana

Drinking water contaminated by pathogenic micro-organisms increases the risk of infectious gastrointestinal disease which could potentially lead to acute kidney injury and even death, particularly amongst the young and the elderly. Earlier studies have shown a substantial reduction in the incidence of diarrheal disease over a period of one year using a polysulfone membrane water gravity-powered water filtration device. The current report is a continuation of these studies to assess the long-term effects of the innovative method on diarrheal incidence rates over a 4-year follow-up period. This follow-up study monitored the trend of self-reported diarrheal events in all households in the previously studied villages for 5 months, in the last half of each study year, using the same questionnaire utilized in the earlier study. Three villages that had no device yet installed served as controls. We computed monthly diarrheal incidence rates for all study years (standardized to per 100 person-months) and compared these to the pre-device incidence rate in 2018 and in the control group, using the Wilcoxon rank sum exact test. The average diarrheal incidence rates of 1.5 p100pm in 2019, 2.19 p100pm in 2021, and 0.54p100pm in 2022 were significantly different from an earlier study that reported 17.8 p100pm rates before the devices were installed in 2018, (all p-values < 0.05). Concomitantly, self-reported diarrheal infections were substantially higher in the “control villages” not yet having the filtration device installed (80.9, 77.6, and 21.5 per 100 pm). The consistent and large reduction in diarrhea incidence documents the long-term efficacy of the use of the membrane filtration device. This simple water purification method using gravity flow improves public health in remote regions with limited resources.