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The sedimentology of the Garubathan alluvial fan of north Bengal foothills is a product of Himalayan neotectonics and monsoon climate. The active neo-tectonics of the Main Central Thrust (MCT), Ramgarh Thrust (RT) and Ghis Transverse Fault (GTF) produce a huge amount of angular clasts in the upper reaches of the river Chel and Mal. During the wet season, either sediment flow by gravity or turbulent stream flow or both, move the clasts to the downhill. The tectonic zone of Main Boundary Thrust (MBT) and Main Frontal Thrust (MFT) are relative passive thrusts than the MCT, RT and GTF in the study area. A very low angle slope is observed in the area of MBT and MFT of the study area. So, the downhill deposition occurred in MBT and MFT zones of the study area. The river Chel and Mal are perinial rivers. During dry periods (pre-monsoon and post-monsoon), in the absence of sediment flow by gravity or turbulent stream flow, the low stream competency deposit the fine sediments. To identify the depositional environments three, seven and six lithofacies varieties were identified in the upper, middle and lower fan surfaces, respectively. The non-cohesive sediment flows by gravity deposited large angular boulders, cobbles and pebbles in the upper fan area. These deposits are either chaotic, unsorted, un-imbricated or graded and imbricated. Deposition of sand is scanty. Both, sediment flow by gravity and fluvial processes deposited angular to round clasts with matrix in the middle fan area. In this area the deposits are reverse graded, reverse to normally graded, laminated and cross-bedded. The high facies diversity of this area indicates highly variable nature of the depositional environments. In the lower fan area, presence of both clast-supported chaotic and matrix-supported laminated or cross-bedded layers suggests a complex nature of the depositional environment of sediment flow by gravity and fluvial processes. [ABSTRACT FROM AUTHOR]

Deep-marine two-part strata consisting of a sand-rich basal part overlain sharply by a mud-rich upper part have been termed linked debrites, hybrid event beds, transitional flow deposits, and bipartite facies. In continental slope and proximal basin floor strata of the Neoproterozoic Windermere Supergroup (western North America) and distal basin-floor strata of the Ordovician Cloridorme Formation (eastern North America), bipartite facies form the middle of a depositional continuum hundreds of meters long consisting upflow of thick-bedded, matrix-poor sandstone (<20% detrital mud matrix) to thin-bedded, sandy mudstone (50%–90% mud matrix). This consistent lithofacies change is interpreted to reflect particle settling in a rapidly but systematically evolving, negligibly sheared sand-mud suspension developed along the margins (Windermere) and downflow terminus (Cloridorme) of a high-energy, mud-enriched avulsion jet. In both study areas, beds of similar lithofacies type succeed one another vertically and transform to the next facies in the depositional continuum at about the same along-strike position, forming stratal units two to nine beds thick whose grain-size distribution gradually decreases upward. This spatial and temporal regularity is interpreted to be caused by multiple surges of a single, progressively waning turbidity current, with sufficient lag between successive surges for the deposition of a traction-structured sandstone overlain by mudstone cap. Furthermore, the systematic back-stepping or side-stepping recognized at the stratal unit scale is interpreted to have been driven by a combination of knickpoint migration and local topographic steering of the flows, which continued until the supply of mud from local seafloor erosion became exhausted, the main channel avulsed elsewhere, or a new stratal element developed. [ABSTRACT FROM AUTHOR]

The International Ocean Discovery Program cored five sites during Expeditions 372 and 375 to investigate the Hikurangi margin, offshore Poverty Bay, North Island, New Zealand. Trench‐wedge deposits were recovered at Site U1520, and the frontal accretionary prism was cored at Site U1518. Based on X‐ray diffraction analyses of the clay‐sized fraction, illite and smectite are the dominant clay minerals. Compositional scatter is unusually large, and a well‐defined mixing trend is evident between illite‐rich and smectite‐rich end members. The proportion of smectite ranges from 9 to 59 wt.% at Site U1518 and from 12 to 62 wt.% at Site U1520. Nearby slope deposits at Sites U1517 and U1519 are more homogeneous, with consistently higher proportions of smectite. The East Cape Current is probably responsible for transporting smectite‐rich suspensions towards the south‐west from sources that include the Taupo Volcanic Zone. Illite‐rich muds require different sources and different routing paths to the trench. Some suspended sediment probably originated in the Waipaoa watershed on the North Island, entering the trench via Māhia Canyon. Other gravity flows probably started in Kaikōura Canyon or Cook Strait and moved towards the north‐east, down the trench's axial channel. The influence of turbidity currents on clay composition changes with water depth, as do the effects of reworking by contour currents and the role of passive hemipelagic settling. The broad continuum of clay compositions in the trench is enhanced by variable amounts of mixing among multiple ocean currents and fluctuating durations of suspension within a bottom nepheloid layer. That complexity deviates from the paradigm of turbidite‐dominated trench wedges. The margin's compositional diversity also complicates the goal of predicting or modelling three‐dimensional variations in frictional, geotechnical and hydrogeological properties. Those lithological properties are important because they affect slope stability along strike and changes in fault‐slip behaviour along the subduction interface. [ABSTRACT FROM AUTHOR]

Hemipelagites are widespread fine‐grained sediments found from shelf margin to deep‐water environments, and they are considered to have been formed as background sedimentation by vertical settling and slow lateral advection of clastic and biogenic fine‐grained particles. Downflow variation in hemipelagic sedimentation, however, is not yet clearly understood, and was investigated in the lower Pleistocene Kiwada and Takamizo formations in the Kazusa forearc basin on the Boso Peninsula, Japan. Mapping of three tephra key beds enabled detailed correlation of two hemipelagite beds over a distance of ca 30 km from shelf‐margin to basin‐plain environments. The sedimentation rates decreased gradually in the downslope direction, but increased locally in response to turbidite sedimentation. This downslope variation indicates that hemipelagic sedimentation is not necessarily constant and varies in response to progradation and retrogradation of deep‐water depositional systems, as well as additional input of fine‐grained sediments from turbidity currents. In contrast, the grain size, magnetic susceptibility, clay‐mineral composition, total organic carbon contents relative to total nitrogen contents (carbon/nitrogen), and δ13C values of organic carbon do not exhibit distinct downslope variation. This downslope consistency indicates that hemipelagites document temporal perturbations of geological and palaeoclimatic conditions in hinterlands, regardless of spatial and temporal variations in deep‐water depositional environments. The concentrations of total organic carbon, total nitrogen and five biomarkers were lower values in turbiditic mudstones and hemipelagites that formed above a turbidite bed than in those of the other hemipelagites. This variation suggests that an additional supply of fine‐grained sediments from turbidity currents likely diluted the organic matter in the hemipelagites. In addition, hemipelagites for which deposition was affected by turbidity currents exhibit slightly lower δ13C values, and may also document an additional contribution of terrestrial organic matter from turbidity currents. [ABSTRACT FROM AUTHOR]

The Upper Oligocene to Lower Miocene (Zhuhai Formation) in the Pearl River Mouth Basin of the northern South China Sea contains extensive shelf‐edge delta and linked slope fan deposits, and records the sediment dispersal and constraint processes. According to the integrated analysis of well‐log, seismic and core data, depositional architecture and delivery mechanism of sandy deposits from the shelf margin to the lower slope are documented systematically. Four major depositional facies are identified: shelf‐edge incised channels and shelf‐edge deltas; amalgamated slump‐channel complexes; slope gullies; and slope fan deposits. Incised channels at shelf‐edge delta front (2.0 to 4.4 km wide) comprise V‐shaped single channels and W‐shaped or irregular‐shaped channels which eroded shelf‐edge sandy deltaic deposits and retransferred them to the lower slope. Further slumping along channel walls may be triggered by the continuously channel downcutting process; and then these incised channels amalgamated and collapsed downslope to generate large‐scale coalesced slump‐channel complexes (15 to 35 km wide), which are regarded as the main delivery system to transport sandy deltaic deposits to the deep‐water basin. There are a series of V‐shaped or W‐shaped slope gullies (tens to hundreds of metres wide) developed along the lower slope, which further delivered sediments to slope fan systems. Slope fan systems are composed predominantly of basal debris flow massive and sandy turbidite channel and frontal splay deposits comprising one of the most important oil and gas reservoirs in the study area. Channelization and large‐scale slumping along the shelf‐edge delta front are regarded as the most important dispersal mechanisms delivering sandy sediments across the shelf margin. Falling sea level was suggested to be one of the important factors causing the incision and large‐scale shelf margin slumps, whereas the unstable high (800 to 1200 m) and steep (5° to 8°) shelf‐edge delta and slope clinoforms provide a pre‐condition for large‐scale shelf‐edge collapse. [ABSTRACT FROM AUTHOR]

Refrigeration and air conditioning plays a vital role in domestic and industrial heating, cooling, refrigerating and ventilation but they are contributing to ozone layer depletion and global warming due to unfriendly refrigerants and consume 33% of the world energy. The condenser is an important component of the vapor compression system which contained 30% of the refrigerant charge. The versatile one ton of refrigeration system is designed, developed for testing minichannel condenser for different condenser temperature and pressure by providing artificial condenser compartment with three air heaters of 2.2 kW capacity each with a multispeed condenser fan for controlling air velocity. Thus, the condensation temperature is reduced by 2 to 3°C due to its special geometry, passes provided, efficient cooling and the coefficient of performance increased by 10 to 15% for condensation temperature varying from 40 to 55°C whereas evaporation temperature varies from -10 to +15°C. Computational Fluid Dynamics (CFD) simulation for different sections of the minichannel condenser such as a single minichannel, single tube with 10 minichannels, first, second, third, fourth passes with varying tubes and entire condenser with all four passes for different inlet and exit temperature are performed using ANSYS FLUENT-20 CFD turbulence models and validated with the experimental results. The pressure and temperature counters for all the sections are studied and plotted. It is found that the temperature difference between experimental and CFD results are within ±15% for all the simulations along the condenser. [ABSTRACT FROM AUTHOR]

In this study, we present evidence of a Paleocene-Eocene Thermal Maximum (PETM) record within a 543-m-thick (1780 ft) deep-marine section in the Gulf of Mexico (GoM) using organic carbon stable isotopes and biostratigraphic constraints. We suggest that climate and tectonic perturbations in the upstream North American catchments can induce a substantial response in the downstream sectors of the Gulf Coastal Plain and ultimately in the GoM. This relationship is illustrated in the deep-water basin by (1) a high accommodation and deposition of a shale interval when coarse-grained terrigenous material was trapped upstream at the onset of the PETM, and (2) a considerable increase in sediment supply during the PETM, which is archived as a particularly thick sedimentary section in the deep-sea fans of the GoM basin. Despite other thick PETM sections being observed elsewhere in the world, the one described in this study links with a continentalscale paleo-drainage, which makes it of particular interest for paleoclimate and source-to-sink reconstructions. [ABSTRACT FROM AUTHOR]

Coarse‐grained subaqueous fans are vital oil and gas exploration targets in the Bohai Bay basin, China. The insufficient understanding of their sedimentary processes, depositional patterns, and controlling factors restricts efficient exploration and development. Coarse‐grained subaqueous fans in the Yong'an area, Dongying Depression, are investigated in this study. These fans include nearshore subaqueous fans, and sublacustrine fans, and their sedimentary processes, depositional patterns and distribution characteristics are mainly controlled by tectonic activity and paleogeomorphology. Nearshore subaqueous fans developed near the boundary fault during the early–middle deposition stage due to strong tectonic activity and large topographic subsidence. Early sublacustrine fans developed at the front of the nearshore subaqueous fans in the area where the topography changed from gentle to steep along the source direction. While the topography was gentle, sublacustrine fans did not develop. During the late weak tectonic activity stage, late sublacustrine fans developed with multiple stages superimposed. Frequent fault activity and related earthquakes steepened the basin margin, and the boundary fault slopes were 25.9°–34°. During the early–middle deposition stage, hyperpycnal flows triggered by outburst floods developed. During the late deposition stage, with weak tectonic activity, seasonal floods triggered hyperpycnal flows, and hybrid event beds developed distally. [ABSTRACT FROM AUTHOR]

Pin valley is an ideal area for alluvial fans' development. Being least disturbed and devoid of vegetation, fans of this area provide exquisite information and extraordinary opportunity to understand different factors that affect their morphology. Despite aforesaid advantages these fans are hitherto not studied. Thus, the present study is an attempt to understand the morphology of these fans and explore factors affecting fan morphology, primarily through morphometry. Data were derived from various satellite imageries, topographical sheets, DEM and field observations. Various parameters of 51 fans and of their basins were measured and relationships among different parameters were examined. The results of the study are generally comparable to literature though these fans are much steeper than their counterparts in similar environmental settings. Multi-proxy approach was used to explore controlling factors. Fan Conicality Index (FCI) and sweep angle of fan (SA) suggest confinement imposed by surrounding environment has considerably reduced the size of these fans. Further, valley-floor width to height ratio (Vf), feeder channel and geological group-wise analyses reveal that active tectonic attitude, order of feeder channel, lithology and characteristics of contributing basin along with associated depositional processes exercise significant control on morphology of these fans. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Geomechanics is the property of Journal of Geomechanics Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Here we show how ultra‐high resolution seabed mapping using new technology can help to understand processes that sculpt submarine canyons. Time‐lapse seafloor surveys were conducted in the axis of Monterey Canyon, ∼50 km from the canyon head (∼1,840 m water depth) over an 18‐month period. These surveys comprised 5‐cm resolution multibeam bathymetry, 1‐cm resolution lidar bathymetry, and 2‐mm resolution stereophotographic imagery. Bathymetry data reveal centimeter‐scale textures that would be undetectable by more traditional survey methods. Upward‐looking Acoustic Doppler Current Profilers at the site recorded the flow character of internal tides and the passage of three turbidity currents, while sediment cores collected from the site record flow deposits. Combined with flow and core data, the bathymetry shows how turbidity currents and internal tides modify the seabed. The turbidity currents drape sediment across the site, infilling bedform troughs and smoothing erosional features carved by the internal tides (e.g., rippled scours). Turbidity currents with speeds of 0.9–3.3 m/s failed to cause notable bedform movement, which is surprising given that flows with similar speeds produced rapid bedform migration elsewhere, including the upper Monterey Canyon. The lack of migration may be related to the character of the underlying substrate or indicate that turbidity currents at the site lack dense, near‐bed layers. The scale of scours produced by the internal tides (≤0.7 m/s) approaches the scale of features recorded in the ancient rock record. Thus, these results illustrate how the scale gap between seabed mapping technology and the rock record may eventually be bridged. Plain Language Summary: This study presents the highest resolution repeat seafloor mapping surveys to date in a submarine canyon. Centimeter‐scale seafloor surveys were conducted over an 18‐month period at a location ∼50 km from the head of Monterey Canyon. Turbidity currents (rapid, down‐slope density‐driven flows of water) and internal tides (tidal currents that flow along the seabed) were recorded by a seafloor instrument node deployed in the study area. Turbidity currents drape sediment across the bedforms, infill troughs, and smooth out erosional features carved by internal tides. While the turbidity currents caused considerable migration of bedforms in the upper canyon, there was surprisingly no notable migration at the study site. The lack of migration may be related to the relatively coarse nature of the seafloor underlying the bedforms and suggests that the turbidity currents at the site lacked a dense near‐bed layer characteristic of flows farther up‐canyon. The internal tides carved centimeter‐scale scours in the seabed, a scale that approaches that of features preserved in the rock record. This study, therefore, shows how new mapping technology may eventually bridge the scale gap between modern seafloor surveys and the ancient rock record. Key Points: Ultra‐high resolution time‐lapse mapping is combined with flow monitoring and sediment cores to document submarine canyon activityFast turbidity currents fail to cause notable bedform migration, though flows with similar speeds cause significant migration up‐canyonSub‐meter to meter‐scale scours, likely carved by internal tides, approach the scale of features preserved in the rock record [ABSTRACT FROM AUTHOR]

The Paleogene Shahejie and Dongying formations of the eastern Bohai Bay Basin contain >500 m fluvial-deltaic deposits and >600 m deltaic-lacustrine deposits, both of which are important for oil and gas exploration. This study aims to figure out the deposition system distribution within the sequence stratigraphy and predict the exploration target. Sequence boundaries are recognized by unconformities in the seismic profiles and abrupt changes in the well-logging curves (acoustic, spontaneous potential, natural gamma-ray and resistivity), and two second-order and five third-order sequences (SQs1, SQs3 in the Shahejie Formation and SQd1-SQd3 in Dongying Formation) are identified. Four types of depositional system and distribution are determined by well-logging profiles, cores, relative sand content and root-mean-square seismic attributes. The SQs3 sequence is predominantly fan deltas and lacustrine deposits, the SQs1 sequence is predominantly shallow lacustrine deposits, the SQd3 sequence is predominantly braided-river delta, semi-deep lacustrine, and turbidite fan, and the SQd2 sequence is predominantly braided-river delta deposits, whereas the SQd1 sequence is predominantly braided-river deposits. The controlling factors are determined by basin subsidence simulation and fossil data of biological palynology, indicating that tectonic activity is the main controlling factor in SQs3 and SQd3 while climate is the main controlling factor in the SQs1, SQd2 and SQd1 sequences. Combined with the physical properties of sandstone, it is concluded that the beach bar in the SQs1 sequence, turbidite fan in the SQs3 and SQd3 sequences, and thick sandstone in the SQd2 sequence are the important exploration targets. [ABSTRACT FROM AUTHOR]

Goats' health, productivity, and behavior are drastically altered during heat stress. Heat dissipation methods become inadequate when environmental temperatures exceed an animal's internal body temperature. Recently there has been increasingly interested in strategies to reduce thermal stress on livestock. Sprinklers may help reduce accumulated heat and improve goat heat dissipation. Ten indigenous adult dry does were randomly assigned to two treatment groups, the non-cooling group as a control and the treatment group with two sprinkler and fans cooling systems. Feed and water consumption, breathing rate, rectal, external, and ambient temperatures, and relative humidity were recorded daily. For two weeks of the investigation, body weight was recorded once a week. The results showed that the control group consumed more water, and the ratio of water drunk/ dry matter intake tended to be higher than the treatment counterparts. Neither group showed significant differences in dry matter intake. Respiratory rates were greater in the control group compared to the treatment counterpart. Despite the marked difference between climatic conditions of both groups' rooms, no significant difference in rectal body temperatures was found. The temperatures of the eyes and legs were not significantly different in either group. In contrast, the calculated correlation between the rectal temperature with the highest value was found for the negative relation with rump and neck temperature. In conclusion, spraying goats and continual air movement under dry weather alleviate heat stress and improves goat welfare. [ABSTRACT FROM AUTHOR]

Seafloor methane emissions can affect Earth's climate and ocean chemistry. Vast quantities of methane formed by microbial decomposition of organic matter are locked within gas hydrate and free gas on continental slopes, particularly in large areas with high sediment accumulations such as deep-sea fans. The release of methane in slope environments has frequently been associated with dissociation of gas hydrates near the edge of the gas hydrate stability zone on the upper slope, with discharges in greater water depths less understood. Here we show, using data from the Rio Grande Cone (western South Atlantic), that the intrinsic, gravity-induced downslope collapse of thick slope sediment accumulations creates structures that serve as pathways for gas migration, unlocking methane and causing seafloor emissions via giant gas flares in the water column. The observed emissions in the study region (up to 310 Mg year−1) are three times greater than estimates for the entire US North Atlantic margin and reveal the importance of collapsing sediment accumulations for ocean carbon cycling. Similar outgassing systems on the Amazon and Niger fans suggest that gravity tectonics on passive margins is a common yet overlooked mechanism driving massive seafloor methane emissions in sediment-laden continental slopes. [ABSTRACT FROM AUTHOR]

Enclosed depressions, termed pockmarks, are widespread seafloor morphologies, commonly associated with fluid seepage. This study provides the first detailed documentation of pockmarks offshore the South Westland margin of the South Island/Te Waipounamu, Aotearoa New Zealand. Pockmarks are identified from multibeam bathymetry (25-m grid) through manual and semi-automated selection in water depths of 100–2600 m. Pockmarks are most concentrated at 400–850 m water depth on continental slope areas between submarine canyons. A continuum of pockmark morphologies includes – (1) large (>0.5 km2 area) and irregularly shaped pockmarks above partially infilled channels; (2) small and circular pockmarks (∼100–200 m diameter; ∼0.008–0.03 km2 area) occurring between canyons; and (3) elongated and intermediate size pockmarks, generally oriented along-slope and often occurring above buried sediment waves. Elongated pockmarks appear to have been modified by near-seafloor oceanographic and/or turbidity current flows. Pockmark features occur across many locations around Aotearoa, including both the eastern and western margins. Some similar pockmark morphologies are identified in these different tectonic, sedimentary, and oceanographic settings, suggesting that there may be some similarity in formative mechanisms, but clear mechanisms leading to their formation remain enigmatic. [ABSTRACT FROM AUTHOR]

Alluvial fans are found across a range of climates and are built from a combination of fluvial and debris flow processes. Correct identification of process is critical to reconstructing the climate and water histories of alluvial fans on Earth and Mars. Theory and data from subaerial Earth fans are often used to estimate paleoflow discharges and sediment fluxes for martian fans; however, most terrestrial work has been conducted on fans that are in hot, dry climates with runoff sourced from rainfall. This differs from the prevailing interpretation that martian fans were sourced from snowmelt under warming periglacial conditions. To characterize processes and rates of periglacial fan formation, we conducted a field-based study of the Black Mountain alluvial fan in the Aklavik Range, Canada. We observed active fluvial bedload transport as well as several small debris flows that had initiated from ice-filled gullies. Following a runoff event of ~0.005 mm/hr to ~0.2 mm/hr across the fan, we estimated sediment fluxes of ~0.04 m3/hr. Under bankfull conditions, we estimated runoff rates between ~0.01 mm/hr to ~14 mm/hr and corresponding sediment fluxes of ~0.3 m3/hr to ~550 m3/hr. This suggests that moderate flow events, well below the maximum runoff production rates suggested for Mars, are capable of entraining and transporting appreciable amounts of sediment by fluvial processes. However, sedimentological and geomorphological observations suggest that ~67% of the fan was deposited fluvially; the remainder was deposited by mass flows. Our results emphasize the need to take care in interpreting martian sedimentary processes and climate from fan surface morphology alone. [ABSTRACT FROM AUTHOR]

Submarine depressions are common features on the eastern Bahamian seafloor but the genesis of the deepest ones (>4000 m in water depth) is not well understood. We conducted a morphometric analysis and compared them to a worldwide database of rounded depressions, whatever their genesis is. The deep Bahamian depressions are large elongated structures, among the largest on Earth, with a width greater than 1000 m and a depth sometimes greater than 200 m. They extend at the toe of the Blake Bahama Escarpment (BBE), one of the tallest escarpments on Earth. Some of them align parallel to the BBE. Other depressions align along large submarine canyon axes. When aligned along canyon axes, the depressions closest to the canyon head are flanked by a topographic high interpreted as a slope-break deposit, i.e., sediment deposited after flow expansion following a hydraulic jump. Turbidity currents in the carbonate canyon system are not permanent processes, but are rather triggered during sea-level highstands when the carbonate platform is flooded. In addition, some depressions are not located in canyon axes. Consequently, the size and location of the depressions are not likely explained by a simple plunge pool mechanical erosion. Rather, our data suggest that all depressions could be initiated by giant karstic dissolution structures (dolines or sinkholes). Under interpretation, those located in canyon axes are sporadically refreshed by carbonate-laden turbidity currents. The height of the outsized chutes marking the crossing of the BBE by the canyon mouth generates a hydraulic jump allowing sediment deposition toward the bottom of the depression. Large depressions observed at this location in the Bahamas were the result of an initial dissolution phase related to retreat of the BBE and the more recent sediment-laden flow activity. The depressions orientated along canyon axes facilitated the regressive erosion that formed the canyons. At present, the depressions located at canyon mouths act as regular plunge pools. [ABSTRACT FROM AUTHOR]

Submarine canyons commonly occur on virtually all continental slopes. Their varied origins are widely studied but still debatable. Eastward (along-slope)–migrating submarine canyons, with nearly regular spacing, are well developed at the northern South China Sea. High-resolution three-dimensional seismic data show that these canyons are localized in the troughs between sediment waves. The waves were present on the slope since before ca. 10.5 Ma and were especially well developed during the late Miocene (ca. 10.5–5.5 Ma). This interval can be divided into two units, of which the upper unit (SU II) has larger sediment waves and much better-developed canyons compared to the lower unit (SU I). Submarine fans developed at the canyon mouths within SU II at the downdip termination of the confinement caused by the sediment waves. Gravity currents were captured between the waves, resulting in erosion mainly along the troughs between them. The canyons were forced to migrate eastward by the migration of the confining sediment waves. In this study, we present a new mechanism for the origin of such regularly spaced submarine canyons for the first time, which we attribute to the formation of regularly spaced sediment waves generated by contour currents. [ABSTRACT FROM AUTHOR]

Fan‐shaped sedimentary deposits are key indicators of paleoclimate on Mars. The largest example, a multi‐lobed deposit (>1,000 km2) at the outlet of Hypanis Valles, may have formed either subaerially or at the edge of a water body. We used a numerical model to test whether these contrasting basin boundary conditions would cause deposit geometries that are diagnostic and distinguishable from orbit. We compared depositional scenarios with either (a) fully subaerial conditions, (b) a constant water level, or (c) a falling water level. In the model, standing water generates deposits that are thicker, less extensive, and increase in dip angle from proximal to distal locations. Nonetheless, deposit geometries for all scenarios are consistent with orbital observations, which are inconclusive regarding a topset‐foreset break that would indicate standing water. Thus, it is possible that the Hypanis deposits formed subaerially, without a water body onlapping the Mars dichotomy boundary. Plain Language Summary: On the surface of Mars, outcrops of sedimentary rock hold clues to climate conditions in the early history of the planet several billion years ago. Based on satellite observations, a particularly large, fan‐shaped feature has been interpreted as either a sediment fan deposited entirely on land, or instead as a river delta formed at the edge of an ancient lake or ocean. Distinguishing between these scenarios, which imply vastly different amounts of water, is critical to determining ancient surface conditions. We used a computer model to simulate the formation of the sediment deposits under different scenarios and compared the modeled deposits to satellite observations. Results suggest that while previous work has interpreted the Hypanis deposits as remants of a delta marking the edge of an ancient ocean, the deposits could have formed entirely on land and therefore did not require an ancient ocean. Key Points: The Hypanis sediment fan is the largest on Mars and has been previously interpreted as a delta formed near the dichotomy boundaryWe reformulated a numerical model to test if scenarios with and without standing water in the basin cause distinctive deposit geometriesComparison to orbital data suggests that the Hypanis deposits could have formed subaerially and did not require an ancient ocean [ABSTRACT FROM AUTHOR]

Deep-sea turbidite has been used to determine the history of occurrence of large earthquakes. Surface-sediment remobilization is a mechanism of the generation of earthquake-induced turbidity currents. However, the detailed mechanism of surface-sediment remobilization caused by earthquake ground shaking is unclear. To understand how high peak ground acceleration (PGA) caused by a large earthquake can remobilize surface sediments, we determined the age of a surface-sediment core recovered from the mid-slope terrace (MST) of the inner slope of the Japan Trench in northern Sanriku to determine turbidites generated by large historical earthquakes and calculate the PGAs of these earthquakes using an empirical attenuation relation commonly used in Japan. Small offsets in radiocarbon ages and excess 210Pb activities between turbidite and hemipelagic muds suggest that the turbidites in the core resulted from surface-sediment remobilization. 137Cs and excess 210Pb chronologies indicate that the three uppermost turbidites in the core are correlated with three large historical earthquakes, namely the 1968 common era (CE) Tokachi-oki, the 1933 CE Showa–Sanriku, and the 1896 CE Meiji–Sanriku earthquakes. Calculation of PGAs for large historical earthquakes along the northern Japan Trench indicates that a PGA of > 0.6 g is necessary for turbidite deposition in the MST basin. This threshold is larger than that reported for central Sanriku and may vary spatially. Moreover, turbidites in the MST deposits are more frequent in the northern Japan Trench than in the central Japan Trench, suggesting that the occurrence of three types of large M8-class earthquakes in the northern Japan Trench might have contributed to the frequent occurrence of large PGAs. [ABSTRACT FROM AUTHOR]

In submarine settings, the growth of structurally influenced topography can play a decisive role in controlling the routing of sediments from shelf‐edge to deep water, and can determine depositional architectures and sediment characteristics. Here we use well‐constrained examples from the deep water Niger Delta, where gravity‐driven deformation has resulted in the development of a large fold and thrust belt, to illustrate how spatial and temporal variations in the rate of deformation have controlled the nature and locus of contrasting depositional styles. Published work in the study area using 3D seismic data has quantified the growth history of the thrust‐related folds at multiple locations using line‐length‐balancing, enabling cumulative strain for individual structures over time and along‐strike to be obtained. We integrate this information with seismic interpretation and facies analysis, focusing on the interval of maximum deformation (15 to 3.7 Ma), where maximum strain rates reached 7%/Ma. Within this interval, we observe a vertical change in depositional architecture where: (1) leveed‐confined and linear channels pass upward in to (2) ponded lobes with erosionally confined channels and finally (3) channelised sheets. Our analysis demonstrate that this change is tectonically induced and diachronous across the fault array, and we characterise the extent to which structural growth controls both the distribution and the architecture of the turbidite deposits in such settings. In particular, we show that leveed‐confined channels exist when they can exploit strain minima between growing faults or at their lateral tips. Conversely, as a result of fault linkage and increased strain rates submarine channels become erosional and may be forced to cross folds at their strain maxima (crests), where their pathways are influenced by across‐strike variations in shortening for individual structures. Our results enable us to propose new conceptual models of submarine channel deposition in structurally complex margins, and provide new insights into the magnitude of fault interaction needed to alter depositional style from leveed to erosionally confined channels, or to deflect seabed systems around growing structures. [ABSTRACT FROM AUTHOR]

Erosional scars, slumps, slides and debrites (mass‐transport deposits) on submarine slopes form relief that influences turbidity current behaviour. However, the interaction of mass‐transport deposit emplacement kinematics (i.e. rapid emplacement versus creep), the morphology of the evolving seafloor topography and subsequent flow types is complicated. This study describes two outcrop examples of deep‐water, predominantly turbiditic, deposits overlying mass‐transport deposits, from the Eocene slope succession of the Aínsa Basin (Spanish Pyrenees). In both examples, the mass‐transport deposit substrate continued to creep contemporaneously with turbidity current deposition and bypass. In the first case study, structures in the mass‐transport deposits are extensional and oriented parallel to flow. In the second, structures are compressional and oriented perpendicular to flow. Mudstones dominate the slope succession, but deposits overlying mass‐transport deposits form sandstone‐prone accumulations. Lateral confinement by flow‐parallel extensional faults enhanced channel‐formation. Channel incision occurred close to the exhumed fault plane on the hangingwall. Incision ceased as the fault gradually locked‐up, and channels avulsed to the hangingwall of a newly active normal fault, while the abandoned channel was filled by a thinning and fining‐upward succession. Barriers formed where the long axes of compressional anticlines developed in mass‐transport deposits formed perpendicular to flow. Here, turbidites filled the bathymetric lows in the axes of synclines. Continued tightening of synclinal depocentres led to repeated stoss side trapping and upslope accretion of coarse‐grained sediment accumulation. This generated thickening and coarsening‐up, followed by thinning and fining‐upward successions, tracking the decreasing, then increasing flow bypass associated with topographic expression on the mass‐transport deposit. This study shows how post‐emplacement creep, and orientation of topographic features on mass‐transport deposits, influence the routing and deposition of contemporaneous turbidity currents, and illustrates examples of facies successions that could be misinterpreted as the product of other autogenic submarine slope processes, such as lateral migration of sinuous channels, or compensational lobe stacking. [ABSTRACT FROM AUTHOR]

Palaeodischarge estimation is largely undertaken within fluvial settings. However, there are limited palaeodischarge estimates specifically from delta deposits, despite their significance globally. Estimating water palaeodischarges for deltas using catchment‐based approaches developed using data from fluvial settings requires estimating parameters from the rock record (for example, palaeotemperature, palaeoslope and palaeorelief). These may be difficult to determine, leading to under‐estimation or over‐estimation of palaeodischarge values due to differences in process‐form relationships between alluvial rivers and deltas. When a sediment‐conveying fluvial channel enters a standing body of water, delta lobes develop through repeating mouth bar deposition due to flow deceleration, forming a deltaic morphology with distributary channel networks that differ morphologically from those developed in unidirectional flowing alluvial rivers. This study provides empirical relationships determined across five climate regions, using 3823 measurements of distributary channel width from 66 river deltas alongside the trunk river bankfull discharge that feeds into the entire delta, using a hydraulic geometry scaling approach. Empirical relationships are developed from the global delta dataset between bankfull discharge and catchment area (Qb–A), and bankfull discharge and median distributary channel width (Qb–Wmed). These empirical relationships produce very strong statistical correlations, especially between Qb and Wmed, across different climate regions (Qb = 0.34 Wmed1.48, R2 = 0.77). However, both Qb–A and Qb–Wmed relationships have outliers that may be explained by particular hydrological or geomorphic conditions. These new empirical relationships derived from modern systems are then applied to Cretaceous outcrops (Ferron Sandstone and Dunvegan Formation). The comparatively simple scaling relationships derived here produced palaeodischarge estimates within the same order of magnitude as palaeodischarge values previously obtained using existing, more complex approaches. This study contributes to source‐to‐sink investigations by enabling palaeodischarge estimates that intrinsically account for climate impacts on channel geometry at the time of deposition, using measurements of channel width or catchment area of a deltaic outcrop. [ABSTRACT FROM AUTHOR]

While Ediacaran cap dolostones research is a hot topic, detailed sedimentological analysis of barite‐bearing cap dolostones remains scarce. Here, new data are presented from Xiangerwan in northern Three Gorges, South China, to illustrate the sedimentary characteristics, depositional environment and formation mechanism of the barite‐bearing cap dolostone. In ascending order, the succession is divided into: (i) pebbly dolostone; (ii) dolostone with unusual sedimentary structures (for example, sheet cracks and tepee structures); and (iii) barite‐bearing facies. The gravels of the pebbly dolostone record the slow relative sea‐level rise during post‐glacial transgression, with a local terrestrial influence. Sheet cracks and tepee structures represent water escape structures in the supratidal and upper intertidal zone, and gently wavy stromatolites in barite‐bearing facies are deposits typical of the upper intertidal zone. In addition, primary radial length‐slow dolomite cements were originally precipitated at the seafloor. In general, the cap dolostone was formed in a shallow‐water ramp environment. The form and sedimentary characteristics of barites indicate a primary (syngenetic) origin and help to divide the barites into bladed (Type I) and needle‐like (Type II) variants. With the ongoing melting of the Marinoan glacier and water density stratification, the cap dolostone was gradually precipitated, accompanied by exotic gravels input. The stratification persisted, and special sedimentary structures were widely developed. Phosphorus and barium ions were brought up from the deep basin by upwelling, indicated by the flourishing stromatolites and barite fan deposition. Above the sediment–water interface, the Type I barite first grew upward from substrates, then the Type II barite could grow either in the reverse 'V‐shape' cavities between and within the Type I barite clusters, forming rhythm layers with bedded dolomite, or scattered in the laminae of stromatolites or surrounding dolomite. Finally, the formation of barite fans indicates the end of cap dolostone deposition and deeper water sedimentation. [ABSTRACT FROM AUTHOR]

The platy limestone deposit of Vallecillo in northeastern Mexico is dated to the early-middle Turonian (Late Cretaceous) and known to contain a variety of well-preserved vertebrate fossils. One of the most common fish species is the teleost Tselfatia formosa. A review of 149 individuals reveals the presence of two types of body shapes (diamond-shaped and torpedo-shaped individuals) which is interpreted as sexual shape dimorphism (SSD). A unimodal size distribution illustrates a dominance of diamond-shaped specimens, but both body shape types are present in small (young) and big sized (old) individuals. The abundance of well-articulated and complete specimens suggests that T. formosa populated deep levels of the water column, which excluded buoyancy and flotation as well as carcass disintegration near the surface. The reconstruction of the dorsal and anal fins suggests the presence of a membrane between each fin ray and allows for ecological comparison of T. formosa with modern fan fishes. [ABSTRACT FROM AUTHOR]

This paper investigates the influence of water level oscillation and sediment supply volume on shallow‐water delta development by means of a flume experiment. The experiment simulated the natural water level by dividing a cycle of sediment period into four parts: the draught period, the flood period (FP), the interflood period in a falling limb (IPF) and the interflood period in a rising limb (IPR). During the FP, flooding broke former channels and a large amount of sediments were evenly unloaded at the surface of lobes. Erosion often appeared at the beginning of the IPF and was dominant at low stand. Most sediments were concentrated in incised valleys and unloaded at the channel mouth to form a new lobe during the falling limb. Erosional channels and lobes were broken at the IPR. Sediments homogeneously covered the surface of lobes and few new lobes appeared during the period. Different sediment supplies influenced the characteristics of incised valley and channel style. Low sediment supply to the delta was strongly influenced by water level change, while high sediment supply was mainly affected by fluvial processes. Based on the flow sand content of water, channels can be classified into four types: (a) narrow and deep multiple channels, (b) narrow and shallow branch channels, (c) broad and shallow main channels, and (d) broad and deep stable channels. Their width‐to‐depth ratios are 1.1–3.5, 5.1–12.9, 7.3–20.2, 2.6–4.6, respectively. Most mouth bars were initially formed but then broken by water level oscillation and channel bifurcation. The preserved mouth bars were well preserved at the far end of lobes, where they entered the low‐energy environment. [ABSTRACT FROM AUTHOR]

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Copyright of Natural Gas Geoscience is the property of Natural Gas Geoscience and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Natural Gas Geoscience is the property of Natural Gas Geoscience and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The avulsion frequency of coastal‐plain rivers is primarily governed by the rate at which channels become superelevated over neighboring plains, which is itself controlled by multiple factors. Notably, the importance of wave and tidal processes, the rates of relative sea‐level (RSL) change, and the bathymetry of the receiving basin are thought to affect channel morphodynamics and channel‐mouth progradation, thereby controlling streambed aggradation and influencing the avulsion frequency and drainage density of coastal plains and deltas. This work tests the significance of these downstream factors on the avulsion histories of 57 Holocene lowland river systems. A quantitative analysis is performed of relationships between variables that quantify downstream controls and estimations of avulsion frequency, based on the number of avulsion events, active or abandoned channel paths, and delta lobes; measures of spatiotemporal avulsion "density" are also derived by normalizing these metrics by the size of study areas and the number of distinct drainage systems. Relationships between avulsion‐frequency metrics and descriptors of process regime indicate that wave and tidal processes may stabilize coastal channel systems, but also that their influence may be modest. No consistent relationship is seen between avulsion‐frequency proxies and the offshore bathymetric gradient, which in the studied examples does not scale with the rate of shoreline progradation. No evident trend exists between measures of avulsion frequency and estimated rates of either eustatic or RSL fluctuations. Overall, the considered variables do not leave a clear statistical signature in Holocene avulsion histories, suggesting that upstream or intrabasinal factors may represent more important controls. Plain Language Summary: Lowland rivers flowing near marine or lacustrine shorelines are affected by waves and tides, by relative variations in sea or lake level, and by the morphology of nearshore areas. These factors may affect the ability of coastal rivers to "avulse," that is, to establish new channel courses. This is expected because of how certain processes sculpt coastal landscapes: for example, waves may sweep sediment away from river mouths, tides can enhance sediment transfer along distributaries, and sea‐level rise or seaward advance of the shoreline can drive vertical shifts in the elevation of riverbeds. These factors can variably determine the degree to which coastal river channels may become raised above neighboring coastal areas, a situation that makes them prone to diversion to new paths following levee breaching. The significance of these supposed controls is evaluated through statistical analyses of the number of (a) channel diversions, (b) historical channel paths, and (c) landforms or sediment bodies representing increments of delta growth (delta lobes), as recognized in the millennial to centennial histories of 57 fluvial systems. Waves and tides may play a modest role in stabilizing coastal rivers, but the studied factors appear to exert a limited control on river diversions overall. Key Points: Holocene avulsion histories of 57 coastal plain river systems are analyzedRelationships between the intensity of wave and tides and river avulsion frequency are modestRiver avulsion frequency is not related to modern rates of absolute and relative sea‐level change [ABSTRACT FROM AUTHOR]

The Colorado River has flowed across the dextral strike-slip plate boundary between the North American and Pacific plates since the latest Miocene or earliest Pliocene. The Fish Creek-Vallecito Basin (FCVB) lies on the Pacific Plate in southern California, dextrally offset from the point where the modern Colorado river enters the Salton Trough; it contains a record of ancestral Colorado River sedimentation from 5.3–2.5 Ma. The basin stratigraphy exhibits a changing balance between locally derived (L-Suite) and Colorado River (C-Suite) sediments. This paper focuses on the Palm Springs Group (PSG), a thick fluvial and alluvial sequence deposited on the upper delta plain (between 4.2–2.5 Ma) when the Colorado was active in the area, allowing the detailed examination of the processes of sediment mixing from two distinct provenance areas. The PSG consists of three coeval formations: 1) Canebrake Conglomerate, a basin margin that has coarse alluvial fan deposits derived from surrounding igneous basement; 2) Olla Formation, fan-fringe sandstones containing L-Suite, C-Suite, and mixed units; and 3) Arroyo Diablo Formation, mineralogically mature C-Suite sandstones. Stratigraphic analysis demonstrates that the river flowed through a landscape with relief up to 2000 m. Satellite mapping and detailed logging reveal a variable balance between the two suites in the Olla Formation with an apparent upward increase in L-Suite units before abrupt cessation of Colorado sedimentation in the basin. Stable heavy mineral indices differentiate L-Suite (high rutile:zircon index: RZi 40–95) from C-Suite (RZi: 0–20). Both suites have garnet:zircon index (GZi) and apatite:tourmaline index (ATi) mostly above 50, although many L-suite and mixed Olla samples have much lower ATi (20–50), suggesting that the distal floodplain was wet and the local sediment had a longer residence time there, or went through several cycles of erosion and redeposition. Heavy mineral analysis, garnet geochemical analysis, and detrital zircon U-Pb age spectra allow us to quantify the amount of mixing from different sediment sources. These data show that about 30% of the mixed units are derived from the Colorado River and that up to 20% of the L-Suite is also derived from the Colorado River, suggesting that there was mutual cannibalisation of older deposits by fluvial channels in a transitional area at the basin margin. Although this study is local in scope, it provides an insight into the extent and nature of sediment mixing in a two-source system. We conclude that most 'mixing' is actually interbedding from separate sources; true mixing is facilitated by low subsidence rates and the rapid migration of fluvial channels. [ABSTRACT FROM AUTHOR]

Hybrid event beds comprise up to five (H1-H5) vertically stacked divisions, including a basal matrix-poor turbidite sandstone (H1), overlain by a banded sandstone (H2) with alternating matrix-rich and matrix-poor bands; this gives way to a matrix-rich sandstone (H3) which constitutes the "linked debrite". Hybrid event beds include transitional flow deposits, slurry beds and matrix-rich sandstones. The Special Issue "Advances in Sedimentology and Coastal and Marine Geology" has collected significant research articles advancing the state of the art of the corresponding sub-disciplines. [Extracted from the article]

The new approach on depositional conditions of the Messinian evaporites in Zakynthos Island indicates that the evaporites in the Kalamaki and Ag. Sostis areas were redeposited during the Early Pliocene. They accumulated either as turbiditic evaporites or as slumped blocks, as a response to Kalamaki thrust activity. Thrust activity developed a narrow and restricted Kalamaki foreland basin with the uplifted orogenic wedge consisting of Messinian evaporites. These evaporites eroded and redeposited in the foreland basin as submarine fans with turbiditic currents or slumped blocks (olistholiths) that consist of Messinian evaporites. These conditions occurred just before the inundation of the Mediterranean, during or prior to the Early Pliocene (Zanclean). Following the re-sedimentation of the Messinian evaporites, the inundation of the Mediterranean produced the "Lago Mare" fine-grained sediments that rest unconformably over the resedimented evaporites. The "Trubi" limestones were deposited later. It is critical to understand the origin of the "Messinian" Evaporites because they can serve as an effective seal rock for the oil and gas industry. It is thus important to evaluate their thickness and distribution into the SE Mediterranean Sea. [ABSTRACT FROM AUTHOR]

The study on morphology and distribution of sublacustrine fan are necessary for the exploration of oil and gas, which could help to effectively predict the reservoirs of sublacustrine fans. In this paper, the distribution and geomorphology of sublacustrine fans of Dongying Formation in Liaoxi uplift (Bohai Bay Basin, East China) and their controlling factors (including shape and formations) have been analyzed in detail based on seismic, core, and logging data. The main conclusions achieved in this study are: (1) During the sequence of the third member of Dongying Formation (SQd3), two types of sublacustrine fan, including channelized fan (in channel shape) and non-channelized fan (in tongue shape and lobe shape), developed on the eastern slope of Liaoxi uplift, which inherited the characteristics of sediments structural maturity in braided river delta front (good sandstone sorting and high structural maturity); (2) Steep slope was favorable for forming tongue shape sublacustrine fans with large ratio of length and width, while gentle slope tended to deposit lobe shape fans; high mud content tended to form stable channels with strong erosion on the slope end, while high sand content tended to form continuous lobes with lobe shape; (3) In the basin with uplift, the beneficial combination among provenance, relative lake level change and paleomorphology, determines the development and distribution of sublacustrine fan, and the sublacustrine fan deposits are mainly concentrated in the TST. The Yanshan fold belt in the west provided sufficient sediments to the Liaodong Bay during LST for the development of a sublacustrine fan in the east slope of Liaoxi uplift since the Liaoxi uplift sunk into the water, with the result that the deposition of braided river delta front can overlap the uplift. The incised canyons in the Liaoxi uplift provided the channels for sediments entering into the eastern slope, and the main sedimentary location of lacustrine fans was between two stages of faults. This study could provide a theoretical basis for researching the characteristics and distribution of other sublacustrine fans in similar basin backgrounds. [ABSTRACT FROM AUTHOR]

Seismic, core, drilling, logging, and thin-section data are considered to analyze the reservoir diversity in the east, middle, and west fan of the Liushagang Formation in the steep-slope zone of the Weixinan Sag, Beibuwan Basin. Three factors primarily affect the reservoir differences for steep-slope systems: (1) Sedimentary factors mostly control reservoir scales and characteristics and the drainage system and microfacies. Massive high-quality reservoirs have shallow burial depths. Channel development and sediment supply favor the formation of these reservoirs. The sedimentary microfacies suggest fan delta plain distributary channels. (2) Lithofacies factors primarily control reservoir types and evolution. The diagenesis of high-quality reservoirs is weak, and a weak compaction–cementation diagenetic facies and medium compaction–dissolution diagenetic facies were developed. (3) Sandstone thickness factors primarily control the oil-bearing properties of reservoirs. The average porosity and permeability of high-quality reservoirs are large, the critical sandstone thickness is small, the average sandstone thickness is large, and the oil-bearing capacity is high. Furthermore, the reservoir prediction models are summarized as fan delta and nearshore subaqueous fan models. The high-quality reservoir of the fan delta model is in the fan delta plain, and the lithology is medium–coarse sandstone. The organic acid + meteoric freshwater two-stage dissolution is developed, various dissolved pores are formed, and a Type I reservoir is developed. The high-quality reservoir of the nearshore subaqueous fan model is in the middle fan, and the lithology is primarily medium–fine sandstone. Only organic acid dissolution, dissolution pores, and Type I–II reservoirs are developed. Regarding reservoir differences and models, the high-quality reservoir of the steep-slope system is shallow and large-scale, and the reservoir is a fan delta plain distributary channel microfacies. Weak diagenetic evolution, good physical properties, thick sandstone, and good oil-bearing properties developed a Type I reservoir. The study of reservoir control factors of the northern steep-slope zone was undertaken in order to guide high-quality reservoir predictions. Further, it provides a reference for high-quality reservoir distribution and a prediction model for the steep-slope system. [ABSTRACT FROM AUTHOR]

Based on high‐quality two‐dimensional seismic profiles and well data, the seismic reflection characteristics from the late Pliocene and Pleistocene succession of the Qiongdongnan Basin in the South China Sea have been analysed. The result will help in understanding the sedimentological development of slope areas. Twenty coeval clinothems are recognized and four major clinothem types are distinguished. In addition, three types of shelf‐edge trajectories are recognized. The various parameters of the clinothems are analysed quantitatively and the relationships between the various clinothem types are studied in combination with the controlling roles. It is concluded that: (i) the shelf‐edge trajectories are related to the type of clinothem; (ii) fluctuations in the relative sea level, in combination with variations in sediment supply, result in different clinothem types and geometric parameters; these parameters show interdependencies; (iii) the alternations of progradation and aggradation of clinothems may provide information of the relative sea level and changes in sediment supply; (iv) some lowstand fans could develop at the foot of the slope in the central–eastern part of the basin when the relative sea level started to fall or began to rise. The results of the present study are consequently significant for further quantitative analyses of the characteristics and development of the continental slope, not only in the Qiongdongnan Basin, but also in other basins. [ABSTRACT FROM AUTHOR]

Turbidity currents commonly bypass sediment in submarine channels on the continental slope, and deposit sediment lobes farther down-dip on the flat and unconfined abyssal plain. Seafloor and outcrop data have shown that the transition from bypass to deposition usually occurs over complex zones referred to as channel–lobe transition zones (CLTZs). Recognition of these zones in cores and outcrop remains challenging due to a lack of characteristic sedimentary facies and structures. This paper focuses on Unit E of the Permian Fort Brown Formation in the Karoo Basin, South Africa, in the Slagtersfontein outcrop complex, which has previously been interpreted as a CLTZ. This study integrates thin-section micrographs, sedimentary facies, bed-set and stratigraphic architecture, and palaeoflow directions to achieve a multiscale analysis of CLTZ features. A novel process-based facies scheme is developed to evaluate deposits in terms of the depositional or erosional tendencies of the flows that formed them. This scheme allows bypass to be distinguished from depositional zones by the spatial distribution of certain sediment facies. Areas of net sediment bypass were predominantly marked by erosive sediment facies and a larger variability in palaeoflow direction while depositional areas showed a lower variability in palaeoflow directions. Metre-scale structures in the bypass-dominated area reveal seafloor erosion and scour formation. Field relations suggest the presence of a ∼500 m long mega-scour in the CLTZ. The characteristic structures documented here are applicable for identifying CLTZs in sparse datasets such as outcrops with limited palaeogeographical context and sediment cores obtained from subsurface systems. [ABSTRACT FROM AUTHOR]

This study integrates provenance and statistical data, along with published sedimentological results, applied on the Lower Oligocene submarine‐fan deposits in Pindos foreland basin. Twelve outcrops were analysed using conglomerate clast composition, petrographic and statistical analysis and this integration suggests that the studied deposits were sourced by the Pindos Orogen. Conglomerate clast composition analysis suggests that the studied deposits contain mainly limestone clasts, followed by sandstone and chert clasts. This conclusion is further supported by the petrographic and cathodoluminescence analyses that have been conducted on the conglomerate matrix and, additionally, suggest the influence of a low‐grade metamorphic source. Potential source rock candidates in the Pindos Orogen that provided the detritus in the succession are represented by the Mesozoic carbonates (limestone and chert), the Cenozoic transitional (mixed carbonate and siliciclastic) and the Cenozoic clastic submarine‐fan deposits (sandstone). The rock units of Pelagonian zone likely represent the low‐grade metamorphic source rock. The principal component and cluster analysis of clast lithologies suggest the existence of three compositional clusters, with the first one being controlled by black chert clasts, the second one by sandstone clasts and the third one by limestone and red chert clasts. The upward increase of chert and lithic fragment abundances is ascribed to the progressive unroofing of the Pindos orogenic source regions. This study utilizes the Pindos foreland basin as an example to unravel the contribution of orogenic processes on sedimentary provenance of the adjacent pro‐foreland basins. Furthermore, this study highlights the advantage of implementing a multi‐faceted approach, including statistical treatment in sedimentary provenance. [ABSTRACT FROM AUTHOR]

Canada ratified the United Nations Convention on the Law of the Sea (UNCLOS) in 2003. With that ratification is an obligation to submit data and information to the U.N. pertaining to the limits of the country's extended continental shelf (ECS); the portion of the juridical continental shelf that extends beyond 200 nautical miles. A team of Canadian scientists, managers, and legal experts that included representation from three Federal Departments (Natural Resources Canada, Fisheries and Oceans Canada, and Global Affairs Canada) with additional support from other departments, spent 13 years compiling and acquiring data to provide the scientific evidence to support delineation of Canada's seaward most maritime limit. The submission has the potential to provide Canada with 2.4 million km2 of additional submarine landmass in the Atlantic and the Arctic oceans over which Canada exercises sovereign rights for the purpose of exploring and exploiting its natural resources. Specific information such as the tectonic framework of the continental margin, the geomorphology of the margin and in particular the continental slope, the geologic nature of adjoined ridges, rises, and plateaux, and sediment thickness within adjacent basins are examples of fundamental pieces of geoscientific information needed to substantiate Canada's outermost maritime limits. This paper highlights a number of segments of Canada's continental margins to showcase this scientific evidence and how it is applied in the UNCLOS context. In doing so, the paper demonstrates the geologic complexity of Canada's margins as illustrated in scientific publications that have resulted from these new data collections, while at the same time presenting new scientific evidence and interpretations. This collection of data and information provides a wealth of new knowledge in Canada's offshore regions. The massive data compilation in the Atlantic led to conception of continental margins, in a source-to-sink scenario, as having an equilibrium base level or graded form, comparable to river systems. Departures from this shape relate to the interplay of sedimentary processes and in particular to those processes that do not fit the source-to-sink paradigm. For example, a significant part of the Atlantic margin is shown to be heavily influenced by along-slope geostrophic currents that generated massive contourite drift deposits. These deposits reflect lateral transport of sediment that had a significant impact on the morphology of the margin. The role of mass transport processes in shaping continental margins is also highlighted, and in particular the collapses of entire segments of the margin were observed. The prominent role mass failure processes play in delivering sediment to the adjacent abyssal plain is also critical in the ECS context. These observations challenge the entrenched notion of a continental margin comprising a shelf, slope, and rise and in particular the concept of the "continental rise". Prior to 2006, regions of the Arctic Ocean seaward of the Canadian landmass had fewer than 5000 km of seismic reflection data. The massive efforts of Arctic coastal States to map their margins for ECS purposes have led to a leap in technological advances to acquire data in ice-covered seas and have led to a wealth of new geoscientific knowledge. Perhaps foremost amongst this knowledge is demonstration that Canada Basin is indeed a fully developed ocean basin, albeit significantly infilled with sediment. Based on this knowledge and identification of related structures, new realistic tectonic scenarios for opening of the Amerasia Basin are proposed that include a significant component of transform or strike-slip motions. With seismic velocity and rock sample information, the continental nature of Alpha and Mendeleev ridges has been substantiated. Even bathymetric data were lacking in the Arctic and new editions of seafloor maps now support grids of 500 m spacing; although some regions remain sparse. Once thought to be relatively stagnant, sedimentary processes such as found in many ocean basins were discovered in the Arctic Ocean. Evidence of geostrophic currents, sediment mass failures, and deep-sea turbidity current channels were found to be ubiquitous, even in the deepest parts of the Arctic's basins. [ABSTRACT FROM AUTHOR]

The Browse Basin, now part of Australia`s North West Shelf passive margin, was formed through six major tectonic events, from the Paleozoic to the Miocene, and is a gas and condensate rich province in north-west Australia. In this study we focused on Eocene-Oligocene stratigraphic plays in order to extend the basin`s resources by proposing new prospects that could include reservoirs with both liquid and gaseous hydrocarbons. Lithologic descriptions from wells, structural and depth maps, along with seismic attributes (GSD and RMS Amplitude), were integrated to create a sedimentological model for the evolution of the Prion Fm. We highlighted the fact that the distal zones of the upper part of the Upper Eocene – Lower Oligocene sequence host multiple individual, disconnected, submarine fan systems that create the proper framework for the exploration activity. An interesting prospect was proposed in this project, one that might yield recoverable resources of around 31 MMbbl of oil and 236 BCF of gas (solution gas and free gas cumulated) (Pmean values for volumetric estimates). This is an attempt to unlock oil reserves that currently lack throughout the region. [ABSTRACT FROM AUTHOR]

The conglomerates and sandstones on the castle hill of Starý Jičín Castle, assigned by previous authors to units of different age and tectonic position, were studied from the point of view of petrography and sedimentology in connection with detailed geological survey of the area. Thick-bedded conglomerates are characterized by sharp bases, massive or normal gradation and, in places, by imbrication of coarse clasts. They are product of high-density turbidite currents, debris flow, alternatively some layers may by products of hybrid sediment gravity flow deposits. The clastic component of the conglomerates is highly dominated by Štramberk-type limestones. Clasts of dolomitized limestones, Těšín-type detrital limestones and calcareous sandstones, and altered trachyte occur very rarely. Medium- and coarse-grained calcareous sandstones contain abundant lithoclasts and a relatively small proportion of quartz grains (20-30 %). A comparison with the conglomerate and sandstone of the Palkovice Formation from Kozlovice and Myslík showed considerable similarity. The sediments of both areas range within the upper Turonian--middle Coniacian interval based on previous micropalaeontological data. The conglomerates from Starý Jičín represent the proximal facies of the submarine fan in the lower slope (Kelč Facies Succession of the Silesian Unit), while the gravity flow deposits of the Palkovice Formation represent the more distal facies of the middle part of the submarine fan in continental rise (Baška Facies Succession). Based on sedimentological features, conglomerates from Starý Jičín can be classified as high-density turbidites, debris flow or hybrid sediment gravity flow deposits deposited in the upper part of a submarine fan. High-density and classical turbidites intercalated with claystone interlayers occurs in the Palkovice Formation of the Baška Facies Succession. Such an idea is in accordance with current knowledge on submarine fan architecture and with the assumed morphology of the former Silesian Basin. [ABSTRACT FROM AUTHOR]

Radiocarbon dating marine sediments is complicated by the strongly heterogeneous age of ocean waters. Tephrochronology provides a well-established method to constrain the age of local radiocarbon reservoirs and more accurately calibrate dates. Numerous ultra-distal cryptotephra deposits (non-visible volcanic ash more than 3000 km from source) have been identified in peatlands and lake sediments across north-eastern North America and correlated with volcanic arcs in the Pacific north-west. Previously, however, these isochrons have not been identified in sediments from the north-west Atlantic Ocean. In this study, we report the presence of two ultra-distal cryptotephra deposits; Mazama Ash and White River Ash eastern lobe (WRAe), in Placentia Bay, North Atlantic Ocean. We use these well-dated isochrons to constrain the local marine radiocarbon reservoir offset (Δ R) and develop a robust Bayesian age–depth model with a Δ R that varies through time. Our results indicate that the marine radiocarbon offset in Placentia Bay was -126±151 years (relative to the Marine20 calibration curve) at the time of Mazama Ash deposition (7572 ± 18 yr BP) and -396 ± 144 years at the time of WRAe deposition (1098–1097 yr BP). Changes in Δ R appear to coincide with inferred shifts in relative influences of the inner Labrador Current and the Slopewater Current in the bay. An important conclusion is that single-offset models of Δ R are easiest to apply and often hard to disprove. However, such models may oversimplify reservoir effects in a core, even over relatively short timescales. Acknowledging potentially varying offsets is critical when ocean circulation and ventilation characteristics have differed over time. The addition of tephra isochrons permits the calculation of semi-independent reservoir corrections and verification of the single Δ R model. [ABSTRACT FROM AUTHOR]

The classic fill‐and‐spill model is widely applied to interpret topographic controls on depositional architecture and facies distributions in slope successions with complicated topography. However, this model implies a constant topographic configuration over the lifespan of a turbidite system. In contrast, the impact on patterns of erosion and deposition above dynamic slopes whose topographic configuration varies spatially over time remains poorly investigated. Here, using high‐resolution 3D seismic reflection data and more than 100 wells from a 40 km long stepped slope system (Campos Basin, offshore Brazil), we document the evolution of a sand‐prone turbidite system active during the Oligocene–Miocene transition. This turbidite system was influenced by vertical and lateral deformation, and we propose a new stratigraphic model to explain the resultant depositional architecture. Two depocentres were identified as steps, with channels on the proximal step, and channel–lobe complexes on the distal step, bounded by sediment bypass‐dominated ramps. Lateral stepping of channels on the proximal step, and oblique stacking of the down‐dip lobe complexes, each cut by through‐going channels, indicate multiple fill‐and‐spill cycles. A persistent north‐east‐ward stepping and thickening on the steps are interpreted to reflect lateral tilting of the seafloor driven by salt tectonics. The dynamic substrate prevented the establishment of a single long‐lived conduit across the proximal step, as recorded in systems with fixed topographic configurations. The filling of through‐going channels with mud at the end of each cycle suggests waxing‐to‐waning sediment supply cycles and periods of sand starvation when the lateral tilting dominated and drove avulsion of the feeder channels towards topographic lows. This study demonstrates that subtle dynamic slope deformation punctuated by discrete sediment supply cycles results in complex stratigraphic patterns with multiple phases, and multiple entry and exit points. Repeated cycles of fill‐and‐spill, tilt‐and‐repeat are likely to be present in other stepped slope systems. [ABSTRACT FROM AUTHOR]

Fluvially‐dominated, fine‐grained, shallow‐water deltas are more variable than is generally recognized. Studies of the Mississippi River imply rather persistent river‐mouth jet dynamics, resulting in either progressive channel bifurcation around middle‐ground mouth bars on lobate deltas, or steady channel progradation to form elongate deltas akin to the modern Mississippi Delta. By contrast, satellite imagery and historical maps of less well‐known fluvially‐dominated deltas show diverse river‐mouth deposits, with plan‐form shapes ranging from river‐mouth fans, through splay, triangular, frond and tongue‐shaped mouth bars, to elongate channels with prominent subaqueous levées. Critically, such deposits may vary along individual channels and across or between individual lobes suggesting that jet variability can be normal, and that a spectrum of jets forms a suite of stable river‐mouth deposits. Channel elongation can also be common. In addition to high‐inertia jets and delta‐head or backwater‐mediated avulsion, two further mechanisms are recognized to form elongate channels. Following channel splitting, dominant splits can shoulder aside mouth bars, so that subordinate splits wither and dominant splits extend the parent channel. Alternatively, river‐mouth fans, subordinate distributary networks and lobes may be abandoned, so that a dominant parent distributary is rejuvenated by receiving an increase in discharge, allowing progradation to continue. Individual real‐world deltas are expected to be characterized by a range of river‐mouth deposits, both laterally and over time. However, such variable river‐mouth deposits, and different modes of channel elongation, are not generally considered in models of fluvially‐dominated deltas – omissions that may have significant impact for land remediation projects on modern deltas, and descriptions of the subsurface constructed to aid resource extraction. [ABSTRACT FROM AUTHOR]

The Ulban terrane composed of a thick sedimentary series of Jurassic clastic deposits is located at the junction of the Mongol-Okhotsk and Sikhote-Alin orogenic belts. The results of studying the deposits assigned to the Middle Jurassic Elgon Formation are presented. The structure of the sedimentary succession and sedimentological features, which indicate sand-rich turbidite sedimentation in a setting of sandy lobe of turbidite fans or ramps, are considered and illustrated. The paleocurrent directions measured in outcrops and calculated using the anisotropy of the initial magnetic susceptibility suggest the transport of clastic material from western or southwestern sources. [ABSTRACT FROM AUTHOR]

Sedimentary facies analysis of conglomerate deposits in the Greymouth Rift Basin has identified the latest Cretaceous to Paleocene alluvial fan and fan delta environments on the northwestern side. The Gravelly Braided River Facies Association is interpreted as high energy, braided river streamflow in a streamflow-dominated alluvial fan environment. The Gravelly Delta Front Facies Association was deposited by high bedload mouth bars and channel avulsion. The Gravelly Prodelta Facies Association is interpreted as high-density turbidity currents, and subaqueous debris flows in a fan delta slope environment. Bedding geometries suggest the fan deltas were Hjulström-types formed on lower angle slopes. The gradual decrease in conglomerate thickness from northwest to southeast indicates that the primary basin bounding fault was located offshore to the northwest, most likely the Cape Foulwind-Canoe Fault Zone. Overall facies distribution and paleoflow directions indicate the Greymouth Basin formed as a half-graben in a purely extensional setting with no strike-slip movement. The presence of contemporaneous sub-basins in the West Coast region suggests they likely experienced similar depositional history to the Greymouth Basin. Our findings agree with previous models from the Taranaki Basin that indicate that rifting was purely extensional, suggesting that the West Coast-Taranaki Rift System recorded primarily orthogonal extension. [ABSTRACT FROM AUTHOR]

The question of whether the Mediterranean Sea desiccated during the Messinian salinity crisis (MSC) has been strongly debated for decades. In the Levant Basin, this debate was recently reignited in relation to the latest stage of the crisis after cessation of salt deposition. The desiccation supporters argue that salt truncation--and its subsequent burial by a latest Messinian, clastic-rich evaporitic unit--occurred subaerially on a desiccated seafloor. However, we show that this latest Messinian unit contains a dense net of channels with meanders, levees, and overspill deposits and is very similar to the turbidite channels observed on the modern seafloor. The aggradation characteristics of these buried channels (levee height, channel depth, and channel-floodplain coupling) indicate a marine rather than fluvial origin. Our conclusion adds to the findings of a previous study that salt truncation occurred in deep waters by dissolution. In a wider perspective, we suggest that the flush of clastics into the basin during the last stage of the MSC indicates a combination of wet climate and sea-level rise that started before the Zanclean (earliest Pliocene). [ABSTRACT FROM AUTHOR]

Earthquake-induced submarine slope destabilization is known to cause mass wasting and turbidity currents, but the hydrodynamic processes associated with these events remain poorly understood. Instrumental records are rare, and this notably limits our ability to interpret marine paleoseismological sedimentary records. An instrumented frame comprising a pressure recorder and a Doppler recording current meter deployed at the seafloor in the Sea of Marmara Central Basin recorded the consequences of a Mw 5.8 earthquake occurring on 26 September 2019 and of a Mw 4.7 foreshock 2 d before. The smaller event caused sediment resuspension and weak current (<4 cm s -1) in the water column. The larger event triggered a complex response involving a debris flow and turbidity currents with variable velocities and orientations, which may have resulted from multiple slope failures. A long delay of 10 h is observed between the earthquake and the passing of the strongest turbidity current. The distance traveled by the sediment particles during the event is estimated to have extended over several kilometers, which could account for a local deposit on a sediment fan at the outlet of a canyon (where the instrument was located), but the sedimentation event did not likely cover the whole basin floor. We show that after a moderate earthquake, delayed turbidity current initiation may occur, possibly by ignition of a cloud of resuspended sediment. [ABSTRACT FROM AUTHOR]

There are many issues affecting multi-hole parallel tunneling and long tunnel ventilation, such as insufficient fresh air supplied at the tunnel face, pollution by contaminated winds, and uncoordinated work among multiple fans. In view of these issues, this paper uses the numerical simulation software Fluent combined with the orthogonal analysis test method, and, based on the actual working conditions of Yuelongmen Tunnel on the Chenglan Line, simulates the parameters of the duct, the installation position of the jet fan at the cross channel, and the combined operation status of multiple fans. The main conclusions are as follows: (1) the primary factor affecting the CO discharge from the tunnel face is the distance between the exit of the duct and the tunnel face, and the secondary factor is the diameter of the duct, while the position of the duct is the least influential factor; (2) the jet fan at the intersection of the cross channel should be set close to the pollution source in such a way as to prevent the jet from hitting the windward side of the cross channel and thereby avoid causing the contaminated wind to contaminate the adjacent tunnel; (3) in tunnels in which blasting operations do not occur, the simultaneous use of high-power air supplies and jet fans will reduce the air pressure in the tunnel, generate an air pressure difference with the adjacent tunnel, trap polluted air, and reduce the ventilation effect. [ABSTRACT FROM AUTHOR]