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Autogenic feedbacks can produce large‐scale, organized stratigraphic patterns in alluvial fans, but autogenic depositional signatures of specific upstream boundary conditions remain challenging to interpret. Here, a combination of theory, experiment and field application is used to explore how autogenic lithofacies changes can be interpreted as stratigraphic indicators of upstream boundary conditions. Six experiments were conducted to test the effects of sediment supply and water discharge rates on autogenic advance and retreat of the lithofacies boundary (grain‐size transition) in an alluvial fan with two dominant grain sizes. Migration of the grain‐size transition caused a short‐term zigzag pattern in the grain‐size transition position in the dip‐directional deposit section. For each experiment, time‐lapse images and laser topographic scans of the fan surface and stratigraphic cross‐sections of the final deposits were used to quantify characteristic timescales of autogenic processes. Timescales for fan‐margin migration, surface wet‐fraction change and grain‐size transition migration generally shorten as sediment supply rate increases and water discharge rate decreases. Increasing the sediment supply rate shortens the duration of the fluvial sediment storage and release cycle, producing higher frequency zigzags in the grain‐size transition trajectory. Increasing the water discharge tends to widen channels and lengthens the duration of the fluvial sediment storage and release cycle, constructing lower frequency zigzags in the grain‐size transition trajectory. Increasing the water discharge also enables more sediment to transport further downstream during release events, leading to higher magnitude zigzags in the grain‐size transition trajectory. These relationships between upstream boundary conditions and the grain‐size transition trajectory demonstrate how autogenic stratigraphic signals could be used as a tool to infer relative changes in boundary conditions. [ABSTRACT FROM AUTHOR]

Continental margins that exhibit high terrigenous input are generally located near deltas that are capable of transporting large quantities of sediments into the basin. However, in rare cases, high terrigenous sedimentation occurs in regions deprived of major riverine systems where the sedimentary pathway is enigmatic. One such case is the Neogene of the Pelotas Basin of Brazil and Uruguay, adjacent to the La Plata River mouth. Since the Miocene, anomalous sedimentation formed a giant progradational wedge, the Rio Grande Cone, one of the largest submarine fan-like features on Earth. To understand the Neogene evolution of the margin and the origins of the Rio Grande Cone, here we present a seismic-stratigraphic framework based on well-logs and 2D seismic data. Three depositional environments are identified: (1) on the shelf, upper Miocene to Pliocene fluvial channels delivered sand deposits on the mud-dominated shelf; (2) on the slope, sediment instability resulted in structural deformation and multiple phases of mass transport deposition and (3) on the lower slope and basin floor, large contourite drifts formed by sediment reworking. We classify the Rio Grande Cone as a megaslide complex, due to its depositional and structural setting. Local deltaic systems were active on the shelf in the Neogene, but the limited size of their paleo-drainage systems in comparison to the volume of sedimentation in the margin suggests that an additional sedimentary pathway existed. In this sense, the demise of an epicontinental sea over the La Plata Basin during the Neogene likely enabled the input of large volumes of fine sediments into the margin, via the La Plata plume water. We suggest that the desiccation of this epicontinental sea and the intensification of ocean currents since the middle Miocene explains the anomalous Neogene terrigenous influx into the SW Atlantic margin. [ABSTRACT FROM AUTHOR]

The Late Miocene source terrane tectonic history in the southern Gulf of Mexico Basin, as informed by detrital zircon geothermochronology data, supports a detailed regional palaeogeographic reconstruction from palaeoshoreline to the deepwater Zama minibasin of the Sureste salt basin. Seismic mapping points to a trio of pathways that converge upon two entry points into the Zama minibasin, illuminating how sediment gravity flows transit a complex seascape defined by shallow salt bodies. Consideration of empirical scaling relationships within and between segments of this sediment dispersal system allows for testable predictions of Upper Miocene submarine fan-runout lengths over basin exploration areas. Distances from the reconstructed shelf-margin to the Zama wells vary around 100 km, an increase of 20% over a straight-line distance as flows likely navigated around extant salt stocks, walls and sheets. This 100-km fan length is about 40% of the reconstructed minimum palaeo-river length, within predicted ranges for smaller source-to-sink systems in tectonically active areas (25 to 50%). The estimated fan-runout distance can be extended even further basinwards, considering the contemporaneous passage of the mobile Chortis block along the Tonala shear zone, expanding the Palaeo-Rio Grijalva drainage network during the Tortonian. These Late Miocene deepwater systems linked to the Palaeo-Rio Grijalva differ substantially from onshore Mexico-sourced turbidity flows feeding into the axis of the north-trending Veracruz Trough. Textural data from wells here suggests these systems were less effective at larger grain transport and sorting. Local (intrabasinal) variations are also evident within the Zama minibasin, as well data (image logs and cores) indicate that axially oriented sediment gravity flows involved fewer high-density turbidities, depositing lower net-to-gross sandstones and thicker shales than those flowing transverse to the basin axis from a southeastern basin entry point. These interpretations will guide both local exploitation of these economic resources and could also support future exploration for analogous salt-influenced deepwater reservoir systems in the Sureste basin and globally. [ABSTRACT FROM AUTHOR]

The submarine fan with a narrow shelf is usually reactive to environmental signal propagation; however, source-to-sink functioning can be further complicated by several allogenic forcings. Here, we document the high-frequency provenance variations and different sediment delivery models recorded in the late Triassic Zhuoni fan developed in the northeastern Paleo-Tethys Ocean, mainly based on process-based sedimentological and provenance study of the Panyuan section in the West Qinling area in the northeastern margin of Tibetan Plateau. High-, low-density turbidites, hybrid event beds and hyperpycnites are distributed in the lobe-dominated submarine fan succession. Field sedimentological evidence from surrounding outcrops suggests that shelf-edge failure was the main cause of most high-and low-density turbidites with the overall absence of submarine slides or slumps, whereas the narrow shelf configuration together with late Triassic humid pulses is favourable for the occurrence of flood-related hyperpycnites in the Zhuoni fan. Detrital zircon grains (N = 6; n=123-272) generally have Palaeozoic-Mesozoic ages (ca. 350-250 Ma and 500-400 Ma) and Neoarchean-Paleoproterozoic ages (ca. 2100-1750 Ma and 2600-2400 Ma), but they can be further categized into three age groups due to different proportions of Precambrian age populations. The results demonstrate that the potential source areas may include the South and North Qinling Orogenic Belt, Qilian Orogenic Belt, different segments of North China Craton and the tectonic junction area between the Qinling and Qilian Orogenic Belts. The temporal changes in provenance signals, which are reflected by both the detrital zircon age spectra and heavy mineral assemblages, indicate different contributions of those sources in response to sea-level fluctuation. It could thus give rise to temporal variations between reactive and buffered source-to-sink sediment delivery models of the Zhuoni fan, despite the overall narrow shelf configuration. The development of the lowstand Zhuoni fan was directly related to extrabasinal hyperpycnal delivery from the river mouth and its high-frequency provenance variability recorded different efficiencies of signal transfer through the onshore catchment with significantly influence of temporal storage, fluvial rejuvenation or even regional climate variability. The highstand submarine fan was thought to be formed by shelf-edge failure with sediment buffering in the shelf region, which was associated with a strong magnitude of provenance mixing. Our work provides a new perspective for deciphering the different origins of deep-water sediment delivery in response to high-frequency sea-level and climate changes. [ABSTRACT FROM AUTHOR]

We investigate the chlorine isotope disequilibrium between chlorides in pore fluids and chlorides in seawater and infer its consequences for chlorine isotope exchange between ocean sediment pore fluids and seawater. We illustrate our methodology with pore fluids from two IODP drilled to depths of ≈1000 m (U1456 and U1457) in the Indus River fan dominated by clay-detritus sediments of the western Himalayas. At these two sites, the concentrations of chloride and sodium ions do not show significant changes with depth and remain very close to those of seawater. As a function of depth, however, chlorides show a progressive decrease in 37Cl (downto −2.5 and −1.4 ‰ respectively), while Ca2+ increases and Mg2+ decreases, as commonly observed in clay-rich oceanic sediments. The rate of the δ37Cl decrease is correlated to the lithology and sedimentation rate. Examining the chlorine budget on these two sites, we conclude that: (1) Most of the chlorine (≥96% of the total Cl) is contained in the pore fluids as chlorides, while the chlorine stored in the other sinks (minerals or organochlorine) is generally very minor (representing <4% of the total Cl). (2) These other sinks are too small to sequester the lost 37Cl-enriched chlorine, which could compensate for the decreased δ37Cl of the chlorides observed in the pore fluids (assuming that the pore fluids originally had chlorides with the chlorine isotopic composition of seawater, δ37Cl = 0 ‰). (3) This lost 37Cl-enriched chlorine has been released from the sediment into the overlying seawater, with fluxes of about 20 mol of chloride per square metre per kiloyear. In order to evaluate the consequence of this unbalanced on a global scale, we extend this chlorine budget analysis to 22 other oceanic sites drilled by IODP in a variety of tectonic environments. It is estimated that worldwide oceanic sediment pore fluids contain 1 × 1020 mol of chloride with mean δ37Cl at −2.3 ± 0.1 ‰ and mean chlorinity at 0.290 ± 0.055 mol Cl- per kg of sediment. Most of the calculated values of the lost 37Cl-enriched chlorine flux are between 3.5 and 45.6 mol of chloride per square metre per kiloyear (mean value of 18.3 mol Cl.m−2.kyr−1), corresponding to a typical chloride exchange time between sediments and seawater of between 5.5 and 71 Myr with a mean value of 14 Myr. Importantly, in oceanic sediments, a relationship between the δ37Cl of the chlorides in their pore fluids and the nature of the detrital minerals (smectite, illite, kaolinite, carbonate, quartz, ...) may exists. This relationship should be modulated by the detrital input from the continents to the oceanic sediments and should therefore be a consequence of the climatic conditions on the continents (mainly rain, temperature). The δ37Cl of the seawater should vary according to these detrital inputs. The expected range of variation would be between −0.3 and +0.3 ‰. This is consistent with the range of δ37Cl in seawater predicted by the study of evaporites deposited since 2 Ga (Eggenkamp et al., 2019). [ABSTRACT FROM AUTHOR]

Geomorphological and sedimentological research carried out in the vicinity of Vilnius (SW Lithuania) aimed to determine the age and stages of development of gullies in relation to climatic conditions and human activity. Two gullies located on the northern slope of the Vilnia river valley were examined in detail. The sedimentological features of the sediments which form fans at the mouths of the gullies were analysed. Three main lithological units were distinguished. On the basis of radiocarbon datings, the beginning of gully erosion was determined to be in the Middle Ages. This process began with intensive settlement in this area. Further stages of a cutting which were distinguished include early modern times and the period from the seventeenth century to the present day. [ABSTRACT FROM AUTHOR]

The most extensive coverage of surficial sediment samples collected to date on Egypt's Nile Delta coast and shelf is needed to better define sediment dispersal patterns across this setting's rapidly eroding margin. Changes in time are now induced by River Nile sediment cutoff by dams, sea level rise, marked shelf subsidence, and regional climate changes, which have altered the amounts and components of sediments; these require replacement, along with the implementation of more effective coastal protection measures. Multiple computer-generated offshore maps depict the distributions and proportions of sand, silt, and mud; the mean grain size and standard deviation (sorting); heavy mineral concentrations; and carbonate content. Heavy mineral lobes at the coast and offshore identify former Nile branch sites. Channel lobes extending seaward resulted from their progradational phase and from the delta's altered sedimentation from the early to late Holocene. The progressive deposition and erosion of these fossil fluvial lobes, and of two active Nile channels, selectively removed their quartz and less dense minerals, thus concentrating heavy minerals on the coast and inner shelf. The prolonged dispersal of original sediment effluence from relict and recent Nile tributaries induced variable depositional patterns on the present shelf. These coastal depocenters, along with extensive sand, silt, and mud from shelf sediments, were reworked further seaward and dispersed by bottom currents, thus masking most previous onshore-to-offshore transport patterns. The major surficial features document long-term responses to the diverse dispersal that influenced the shoreline to the outer shelf deposits from the Pleistocene to the present. [ABSTRACT FROM AUTHOR]

Sediment gravity flows exhibit a large range of flow behaviours, making their flow dynamics hard to predict and the resulting deposits a challenge to interpret. Cohesive sediment gravity flows containing clay are particularly complex, as their behaviour is controlled by the balance of turbulent and cohesive forces. A first set of laboratory lock‐exchange experiments investigated the effect of adding 25% very fine sand by volume to high‐density cohesive sediment gravity flows with strongly suppressed turbulence. This caused these mixed clay–sand flows to become more cohesive, have shorter runout distances, and have lower head velocities than the original pure‐clay flows, despite the increase in density difference and the non‐cohesive properties of the sand. Yield stress measurements confirmed that adding the non‐cohesive very fine sand increases the cohesive strength of dense clay suspensions. This higher cohesive strength outcompetes the enhanced density difference and reduces the flow mobility. A second set of experiments across a larger range of clay concentrations showed that, for low‐density cohesive sediment gravity flows dominated by turbulent mixing, the addition of 25% very fine sand increased the head velocities because of the enhanced density difference and weak cohesive forces. Thus, the addition of very fine sand may increase or decrease the mobility of cohesive sediment gravity flows, depending on the initial type of flow and the balance between turbulent and cohesive forces. In the natural environment, this study proposes that very fine sand can only increase the cohesive strength and reduce the flow mobility of cohesive sediment gravity flows that have a sufficiently strong matrix strength to fully support the sand particles. The contribution of very fine sand to the cohesive strength of high‐density cohesive sediment gravity flows may have important implications for flow transformation on submarine fans, especially in distal regions where transient–turbulent, cohesive flows are particularly common. [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]

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]

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]

Sediment supply is widely believed to be a key control on alluvial fan morphology and channel dynamics. Although the sediment supply to natural fans is rather episodic, experimental studies of alluvial fans often use constant sediment supply rates, making it difficult to relate fan dynamics to the magnitude and frequency of sediment supply in the field. This paper presents a series of experiments designed to test the impact of episodic sediment supply on fan evolution and dynamics. We compare four experiments, each with the same mean sediment supply but different durations of high- and low-supply periods. The experiments show that fan morphology and channel dynamics respond systematically to the temporal elongation of sediment supply oscillations: longer supply cycles generate flatter fans with more trenched channels. These results highlight how different basin conditions might generate different fan morphologies: supply-limited basins with intermittent sediment supply might generate fans that are flatter than expected. Our results raise the question of whether a constant sediment supply in experimental models can adequately characterise the dynamics of natural fans in the field. We therefore suggest that experimental modellers should include variability when investigating fan responses to sediment supply. [ABSTRACT FROM AUTHOR]

The article highlights the dynamics of sediment plumes near the release from a deep seabed polymetallic nodule mining preprototype collector vehicle was conducted in the Clarion Clipperton Zone in the Pacific Ocean 4500-m deep. It also discusses that that turbidity current dynamics sets the fraction of sediment remaining suspended and the scale of the subsequent ambient sediment plume.

The offshore margins of Guyana, Suriname, and French Guyana (the "Guyanas Equatorial Margin") have become the focus of active hydrocarbon exploration over the last decade, with significant energy resources discovered since 2015 along both the Guyana and Suriname segments of the margin. Those discoveries are mainly associated with the Late Cretaceous series of the Guyana-Suriname Basin and they shed light to a rare situation where stratigraphic traps are particularly successful. To date, the tectono-stratigraphic evolution of the area has been primarily examined at margin-scale through seismic refraction, rare borehole data and sparse, regional long offset multichannel 2D seismic datasets. In this paper we combine the results from newly acquired high-resolution well data, 2D/3D seismic interpretation and 3D seismic geomorphology, to build a robust and consistent sequence stratigraphic framework and address the evolution of Cretaceous sedimentary landscapes offshore Suriname, with a particular emphasis on the Late Cretaceous strata. The Suriname margin displays a very specific overall sequence stratigraphic evolution marked by four main phases each characterized by distinct sedimentary fluxes and related overall geometries: 1) a margin initiation phase, 2) an aggrading phase, 3) a backstepping phase and 4) a forestepping phase. The Suriname basin initiated in the Early/Mid Jurassic after the emplacement of thick Early Jurassic volcanic series attributed to the Sierra-Leone (or Bahamas) Hotspot (phase 1). This localized early magmatic activity led to two very different configurations: a typical Volcanic Passive Margin in the east along the western border of the Demerara Plateau and a transform segment to the west (essentially along the Guyana margin). The following phase (phase 2) is characterized by the establishment of a Late Jurassic to Early Cretaceous mixed clastic‑carbonate platform with an overall aggradational stacking pattern observed until the Early Aptian. Phase 3 started by significant backstepping, that culminated during the Cenomanian-Turonian transition, coeval with widespread organic-rich marine shale deposition. This overall transgression occurred in four steps: (B) late Early Aptian flooding followed by renewed margin progradation; (C) Early Albian flooding and (D) Late Albian to Cenomanian flooding above the break-up unconformity and (E) the maximum backstep at the Cenomanian-Turonian boundary. This long-term transgressive trend is interpreted as the combination of (1) long-term eustatic rise during the early Cretaceous; (2) high rates of margin subsidence following the Aptian to Albian opening phase of the Equatorial Atlantic, and (3) relatively limited sediment supply rates along the margin at that time. The successive, backstepping shelf-margin wedges created a distinctive stepped profile (paleo shelf-margins) that greatly impacted the geometries of the overlying Late Cretaceous sequences. During this backstepping phase, clastic sediment delivery to the deep-water part of the Suriname basin in the Early Cretaceous was limited and mainly sourced from the large Berbice Canyon complex at the Guyana-Suriname border. The outlet of the Berbice drainage systems may have been anchored by an aborted section of the Jurassic rift and linked to the onshore Takutu graben which separates the Guyana shield in two parts. The fourth phase of the Jurassic to Cretaceous evolution of the Suriname margin is characterized by a dramatic increase of the sediment supply during the Santonian resulting in the accumulation of thick sequences of channel-dominated turbidite fans. This renewed clastic input is linked to a major drainage reorganization on the Guyana shield and is also coeval to the change from the point-sourced Berbice system to a line-sourced input from smaller rivers and deltas along the Suriname margin. From Early Santonian to Late Maastrichtian, the offshore sedimentary systems were then characterized by an overall regression with stacked coastal clastic systems on the shelf and continued fan deposition in the slope together with abundant slope erosion and related Mass Transport Complexes. At higher frequency this long-term forestepping Late Cretaceous trend was modulated by accelerated pulses of sediment supply (and associated margin progradation) during the Middle Santonian, Middle Campanian, and the Early Maastrichtian. From the Santonian turn-around to the Late Maastrichtian, sedimentary systems are deciphered as sequences constrained by biostratigraphic data from the latest industry wells in Block 58 in Suriname and combined with seismic interpretation of both 3D and 2D data. The multi-scale sequence stratigraphic framework built in this study highlights 1) the specific sedimentary architecture of the margin and 2) the role and the impact of external forcing on the sedimentation rate. Moreover, the results highlight the key importance of topographic inheritance (from both structural and sedimentary origin) on deep-water reservoir architecture, that led to important hydrocarbon accumulations through stratigraphic trapping in offshore Suriname. [ABSTRACT FROM AUTHOR]

Fractionation of particles in deep‐water sediment gravity flows is an important factor in the resulting deposit and for discriminating sedimentary environments, but remains poorly understood. Quantitative characterization of particle shape was performed for more than ten‐thousand particles of experimental gravity flow experiments (both of cohesive and non‐cohesive nature) made using coal and kaolin particles. Eleven particle shape parameters were calculated and their distribution and trends within the experimental basin were evaluated. Results indicate the existence of non‐normal distributions and observable correlations between particle shape parameters. Shape parameters such as circularity and roundness are dominant controls on shape variation. Strong correlations exist between mean shape parameters and along‐flow distance from the source for particles in non‐cohesive flow experiments. Important differences were observed between shape parameter distributions of particles sampled at different areas within the experimental basin, which can be grouped based on their depositional setting (proximal or distal) using multivariate statistical analysis, especially for the non‐cohesive flow experiments. A tendency for more elongated and irregularly‐shaped particles at the more distal and marginal areas of the studied experimental basin was observed and validated by previous field studies in real‐world deep‐marine deposits. Besides, fractionation of particles is less‐pronounced in cohesive flows compared with non‐cohesive ones suggesting the soundness of discrimination of depositional settings based solely on particle shape characteristics is strongly dependent on parent flow characteristics. Yet, results highlight the potential of particle shape analysis in revealing spatial particle shape trends due to hydrodynamic fractionation and discriminating different depositional settings within submarine fans. This methodology may be applied to seafloor and subsurface samples to help identify the flow process and depositional environment. [ABSTRACT FROM AUTHOR]

The connection between deltaic clinothem growth and the formation of down-dip deep-water systems on continental margins has been extensively discussed as a crucial component of sequence stratigraphic theory. However, in lacustrine settings, the growth of deltaic clinothems and outlying deep-water fans remains comparatively poorly understood. In the southwestern Bozhong Sag, Bohai Bay Basin, China, both lacustrine deltas and outlying sub-lacustrine fans were developed during the Oligocene, providing an opportunity to investigate the connection between lacustrine deltaic clinothem growth and the formation of outlying sub-lacustrine fans in deep-lacustrine systems. We employ 3D seismic data, well data, core data, and sandstone grainsize data to analyze the stacking patterns and internal architectures of these two sedimentary systems in the lower and upper successions of our study interval, SQE d 2 L. In addition, elemental geochemical parameters were utilized to reveal the paleoclimatic signature of the different stratigraphic successions. Our results suggest that there are two main types of deltaic clinothem stacking patterns in the lower and upper successions of SQE d 2 L, respectively: (1) in the lower succession, progradational to aggradational stacking patterns have a flat to steeply rising rollover trajectory, and (2) in the upper succession, aggradational to progradational and degradational stacking patterns have a slightly rising to flat and slightly falling trajectory. Meanwhile, the sub-lacustrine fans with straight channels and thick lobe complexes are coupled with progradational and aggradational (PA) deltaic clinothems in the lower succession. In the upper succession, small-scale sub-lacustrine fans with sinuous channels and thin lobe complexes are coupled with aggradational to progradational and degradational (APD) deltaic clinothems. The sediment connectivity between lacustrine deltas and sub-lacustrine fans stands in stark contrast to their counterparts in marine basins (such as marine APD clinothems coupled with large-scale deep-water fans, while marine PA clinothems rarely produce deep-water fans). In addition, two contrasting paleoclimatic stages have been identified in SQE d 2 L, namely the earlier humid stage in the lower succession and the later semiarid climatic stage in the upper succession. A comprehensive analysis of the differences between lacustrine and marine basins indicates that climatic variations play a pivotal role in deep-lacustrine deposition. Consequently, a climate-cycle-driven, sediment-supply-dominated sedimentary model of delta-to-fan sediment connectivity is proposed that incorporates the efficiency of terrigenous sediment dispersal into deep-lacustrine floors and the architecture of sub-lacustrine fans. The findings of this study further refine the implementation of the sequence stratigraphy paradigm and enhance the understanding of delta-to-fan sediment connectivity in deep-lacustrine depositional systems. • The scale of deep-water fans is coupled with various lacustrine deltaic clinothems. • Sediment connectivity of delta-to-fan in lacustrine basins is opposite to marine. • Climatic variations regulate sediment-supply and deep-lacustrine deposition. • Humid climates led to increased sediment connectivity between deltas and fans. [ABSTRACT FROM AUTHOR]

The western Ordos Basin is located at the intersection of multiple tectonic units and is a key area in the restoration of the palaeogeographic pattern of the East Asia region. The stability of the area and well-developed Paleozoic strata in the basin provide ideal conditions for revealing the relationships among the tectonic processes apparent there. However, within the constraints of extensive post-depositional modification, poor-quality seismic data, and a lack of wells, sediment dispersion differences, source attribution, and source-to-sink processes are still unclear. In this study, we integrated sedimentology, mineral, and geochemical data obtained from marine, continental, and marine-continental transition sedimentary environments in the study area in order to reveal the evolution from source-to-sink. The results show that the western Ordos Basin was predominantly supplied by the Alxa block, Yinshan orogenic belt, Qilian orogenic belt, and the North Qinling orogenic belt during the Late Paleozoic era. As a result of the closure of the Paleo Asian Ocean, the Alxa block and Yinshan orogenic belt became the primary source areas to the north, being composed of granite and alkaline basalt and some sedimentary rocks. In the southern area, the Qilian and the Northern Qinling orogenic belts were subjected to the PaleoTethys remnant ocean basin subduction during the Early Permian. Granite and alkaline basalt were the source rocks of the North Qinling orogenic belt, which became the source area during the Shanxi period. The Qilian orogenic belt contains some sedimentary rocks. The continuous uplift of the southern and northern orogenic belts. The tectonic setting of the northern source area transitions from a passive continental margin to an active continental margin with a mixture of continental arc. The tectonic setting of the southern source area transitions from a mixture of passive continental margin and active continental margin to an active continental margin and continental island arc. The climate changes gradually from humid to semi-arid and then to arid, and meanwhile, the sea level shows a decreasing trend, leading to an increasing distance of advancement for each source-to-sink system, and gradually converged in the central and eastern regions of the basin. Tidal and fan delta sandy sediments in the study area were transformed into fluvial delta sandy sediments in the northern two source-to-sink systems. The southern source-to-sink systems gradually changed from scattered sandbarrier and coastal sandy sediment to fluvial sandy sediment after the Shanxi Formation. • No apparent source from the North Qinling Belt before Shanxi Formation. • Subduction/collision time difference between Ocean Basins create a north-south difference in dispersal of sandy sediments. • Sandy sediments dispersal in marine-continental transition influenced by climate, sea-level, and basin accommodation space. [ABSTRACT FROM AUTHOR]

Upper‐flow‐regime bedforms, including upper‐stage‐plane beds, antidunes, chutes‐and‐pools and cyclic steps, are ubiquitous in glacigenic depositional environments characterized by abundant meltwater discharge and sediment supply. In this study, the depositional record of Froude near‐critical and supercritical flows in glacigenic settings is reviewed, and similarities and differences between different depositional environments are discussed. Upper‐flow‐regime bedforms may occur in subglacial, subaerial and subaqueous environments, recording deposition by free‐surface flows and submerged density flows. Although individual bedform types are generally not indicative of any specific depositional environment, some observed trends are similar to those documented in non‐glacigenic settings. Important parameters for bedform evolution that differ between depositional environments include flow confinement, bed slope, aggradation rate and grain size. Cyclic‐step deposits are more common in confined settings, like channels or incised valleys, or steep slopes of coarse‐grained deltas. Antidune deposits prevail in unconfined settings and on more gentle slopes, like glacifluvial fans, sand‐rich delta slopes or subaqueous (ice‐contact) fans. At low aggradation rates, only the basal portions of bedforms are preserved, such as scour fills related to the hydraulic‐jump zone of cyclic steps or antidune‐wave breaking, which are common in glacifluvial systems and during glacial lake‐outburst floods and (related) lake‐level falls. Higher aggradation rates result in increased preservation potential, possibly leading to the preservation of complete bedforms. Such conditions are met in sediment‐laden jökulhlaups and subaqueous proglacial environments characterized by expanding density flows. Coarser‐grained sediment leads to steeper bedform profiles and highly scoured facies architectures, while finer‐grained deposits display less steep bedform architectures. Such differences are in part related to stronger flows, faster settling of coarse clasts, and more rapid breaking of antidune waves or hydraulic‐jump formation over hydraulically rough beds. [ABSTRACT FROM AUTHOR]

Morphological scaling relationships between source‐to‐sink segments have been widely explored in modern settings, however, deep‐time systems remain difficult to assess due to limited preservation of drainage basins and difficulty in quantifying complex processes that impact sediment dispersals. Integration of core, well‐logs and 3‐D seismic data across the Dampier Sub‐basin, Northwest Shelf of Australia, enables a complete deep‐time source‐to‐sink study from the footwall (Rankin Platform) catchment to the hanging wall (Kendrew Trough) depositional systems in a Jurassic late syn‐rift succession. Hydrological analysis identifies 24 drainage basins on the J50.0 (Tithonian) erosional surface, which are delimited into six drainage domains confined by NNE‐SSW trending grabens and their horsts, with drainage domain areas ranging between 29 and 156 km2. Drainage outlets of these drainage domains are well preserved along the Rankin Fault System scarp, with cross‐sectional areas ranging from 0.08 to 0.31 km2. Corresponding to the six drainage domains, sedimentological and geomorphological analysis identifies six transverse submarine fan complexes developing in the Kendrew Trough, ranging in areas from 43 to 193 km2. Seismic geomorphological analysis reveals over 90‐km‐long, slightly sinuous axial turbidity channels, developing in the lower topography of the Kendrew Trough which erodes toe parts of transverse submarine fan complexes. Positive scaling relationships exist between drainage outlet spacing and drainage basin length, and drainage outlet cross‐sectional area and drainage basin area, which indicates the geometry of drainage outlets can provide important constraints on source area dimensions in deep‐time source‐to‐sink studies. The broadly negative bias of fan area to drainage basin area ratios indicates net sediment losses in submarine fan complexes caused by axial turbidity current erosion. Source‐to‐sink sediment balance studies must be done with full evaluating of adjacent source‐to‐sink systems to delineate fans and their associated up‐dip drainages, to achieve an accurate tectonic and sedimentologic picture of deep‐time basins. [ABSTRACT FROM AUTHOR]

Sediments deposited on the eastern continental shelf of India are studied for texture, mineralogy and their major, trace, and rare earth elemental composition in lithogenic fraction. The objective of this study was to identify the sources, and evaluate the factors affecting the erosion and weathering in the catchment area and dispersal and deposition of sediments over the shelf region. Here, we present an extensive dataset covering the entire eastern continental shelf of India from the Ganges-Brahmaputra (G-B) basin in the north including the shelf off major peninsular Indian river basins of Mahanadi, Godavari, and Krishna up to the Kaveri basin in the southern tip. Textural and geochemical studies have shown that the lithology of the source rocks plays an important role in governing the chemistry and mineralogy of the sediments. The results show that the G-B shelf sediments are primarily derived from the Higher Himalaya Crystalline sequence (HHCS) and the Tethyan sedimentary series (TSS) exposed along the peaks and drainage divide of the Himalayas. Mahanadi shelf sediments are mainly derived from the felsic rocks belonging to Precambrian metamorphic formations of the Eastern Ghats, limestones, sandstones, and shales of the Gondwanas and recent deltaic alluvium deposits, whereas the Krishna-Godavari (K-G) sediments find a part of their source in the Deccan Basalts. The shelf sediments off River Kaveri are derived from a mixture of peninsular granitic gneisses, tonalite-trondjhemite gneisses, and charnockites. The sediment geochemistry has also allowed us in assessing the weathering patterns in the source areas. The sediments have undergone a moderate degree of weathering. Weathering intensities were found to have varied with the source area lithology. The least square regression of the geochemical data allowed us to estimate the relative contribution of each of these sources and their geographic extent. Unlike the massive offshore deposition and formation of a major Fan system (the Bengal fan), the fluvial sediment dispersal of the mighty Himalayan Rivers on the continental shelf is significant only at the G-B mouth and their contribution reduces to <50% at about 18oN. The sediment dispersal from the Godavari River is seen to extend on either side of the mouth of the river which is attributed to the reversing East India Coastal Current (EICC), which plays an important role, in the sediment transport along the central and south-central part of the east coast of India. The influence of the Mahanadi, Krishna, and Kaveri River sediments is however confined to a small area near their mouths and has a limited geographic extent of influence in the shelf region. • Entire eastern continental shelf of India is geochemically mapped, hithero not done • A distinct provinciality in geochemistry commensurate with source rock lithology is witnessed. • Geographic spread of each contributory source is estimated using mixing calculations • Reversing monsoon currents with season seem to control the sediment dispersal in the area. • Unlike the large geographic spread into deep-sea, spread of G--B derived sediments on the shelf is limited to narrow extent [ABSTRACT FROM AUTHOR]

How and when sediment moves from shallow marine to deep-water environments is an important and poorly understood control on basin-scale sediment dispersal patterns, the evolution of continental margins, and hydrocarbon exploration in deep-water basins. The Golo River (Eastern Corsica, France), its delta, canyons, and fans provide a unique opportunity to study sediment routing from source to sink in a relatively compact depositional system. We studied this system using an array of high-frequency seismic data, multi-beam bathymetry, and five cores for lithology and age control. Movement of sediment to deep water was controlled by interactions between the Golo River, the Golo Delta, and shelf-penetrating submarine canyons. Sediment moved to deep water when lobes of the Golo Delta prograded to the heads of these canyons, or when the Golo River itself flowed directly into one of them. Sand accumulated in canyons, deep-water channels, and submarine fans during glacial periods of low sea level, while mud was deposited throughout the slope, in the relatively short reach of leveed-confined channels, and in the mud-rich fringes around the sandy fans. During interglacial periods of high sea level, the basin was blanketed by mud-rich deposits up to 10 m thick interbedded with distinctive carbonate-rich sediments. Deposition rates in the basin ranged from 0.07 m/ka to 0.59 m/ka over the last 450 ka. Mud deposition rates remained relatively constant at ~0.16 m/ka during all time periods, while sand deposition only happened during glacial periods of low sea level with an average rate of 0.24 m/ka. In addition to sea-level controls on sediment delivery, avulsions of the Golo River and its deltaic lobes preferentially routed sediment down either the North or South Golo canyons. Thus, while the larger, sequencescale architecture of the basin is controlled by allogenic sea level forcing, millennial-scale autogenic processes operating on the shelf and in deep water shaped the distribution of sand and mud, and the internal geometry of the deltas and submarine fans that they fed. While some aspects of the Golo system are characteristic of steep, tectonically active margins, others such as the nature of connections between rivers and shelf-penetrating submarine canyons are observed in most margins with active submarine fans regardless of their tectonic setting. [ABSTRACT FROM AUTHOR]

Drilling and coring during IODP Expedition 362 in the eastern Indian Ocean encountered probably the largest wood fragment ever recovered in scientific ocean drilling. The wood is Late Miocene in age and buried beneath ∼800 m of siliciclastic mud and sand of the Bengal–Nicobar Fan. The wood is well preserved. Possible origins include the hinterland to the north, with sediment transported as part of the submarine fan sedimentary processes, or the Sunda subduction zone to the east, potentially as a megathrust tsunami deposit. [ABSTRACT FROM AUTHOR]

A new two-phase box model is developed in this study for the prediction of a spatially varying turbidity current with sediments on a horizontal bottom. The turbidity current is segmented into small subvolumes to account for the spatial variation with nonuniform spreading, while a two-phase formulation computes the differential settling of the suspended sediments inside the turbidity current, which form deposits onto the seabed. In addition, the new model is capable of simulating the transition from constant flux to fixed volume propagation, which is typical for both natural submarine landslides and engineered barged sediment disposal. The computation is terminated when most of the total sediment volume is deposited, yielding the final deposition pattern. Following the model development, a detailed experimental study was carried out in the laboratory to validate the model predictions by releasing large but finite amounts of sediments through a rectangular opening on the water surface. The agreement between the model predictions and experimental measurements was found to be satisfactory. Finally, this model is integrated into the Barged Sediments Disposal Model (BSDM) software for the assessment of open-water barged sediment disposal. A practical application of the integrated BSDM is demonstrated using a field study reported in the literature. [ABSTRACT FROM AUTHOR]

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

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

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

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

The Bengal Fan, as the largest submarine fan in the world, receives a large amount of sediments discharged from the Himalayas through the Ganges-Brahmaputra (G-B) river system. However, previous studies of this system seldom focused on the role of channels, which are widely developed in the Bengal Fan, in sediment transportation over the last glacial cycle. Here, we discuss the coupled sedimentary archive in two gravity cores along the Active Channel in the Bengal Fan. Our findings are based on grain size, clay minerals, and Sr and Nd isotope compositions of these two sediment cores. End-member modeling of grain-size data reveals that the intermediate end-member represents the flux of distal fluvial particles from the G-B river system, the fine end-member denotes regional sediment supply of weathered volcanic materials, especially from the eastern Indian Peninsula, and the coarse end-member probably reflects nearby terrigenous input, aeolian input and/or volcanic glass. Sediment provenance analysis based on clay minerals, and Sr and Nd isotopes confirmed sediment supply from the G-B river system which was characterized by high illite percentage, high 87Sr/86Sr ratios and low ε Nd values, especially during five stages (50–45 ka, 42–37 ka, 31–28.5 ka, 24–20 ka and 14–9 ka). During these stages, heavy fine-grained sediment supply from the G-B river system was discharged into the study area under the influence of climate change rather than sea-level fluctuation, additionally emphasizing the importance of channels in the sediment transport process. Moreover, we find a significant alteration of sediment sources at ∼26 ka, which may be related to conversion of the deep-water currents in the Bay of Bengal. • There is staged sediment supply from the G-B Rivers into the Bay of Bengal. • Heavy sediment supply of the G-B Rivers was affected by climate change. • The channels developed on the Bengal Fan are important in the sediment transport process. • Sediment source change at ∼26 ka may be related to conversion of deep-water currents. [ABSTRACT FROM AUTHOR]

Abstract Major and trace elements of sediments from two gravity cores (10YDY09 and 12I712) in the northeastern Indian Ocean have been analyzed for sediment provenance and the relationship of the sediments with climate change since 50 ka. The rare earth element (REE) compositions were analyzed, and the sediment contributions were estimated for the major potential sources, including the Ganges-Brahmaputra (G-B), Godavari-Krishna (G-K) and Mahanadi Rivers. Our results showed that the sediments in the study area were a mixture of sediments discharged from the above three rivers. The sediment contribution of the G-K Rivers increased notably during the Holocene when the rainfall increased, which may be caused by the strengthening of the East Indian Coastal Current (EICC) and the resulting large amounts of sediments supplied by the G-K Rivers. The higher sediment contribution from the G-B Rivers demonstrated the role of the Active Channel in transporting sediments to the distal Bengal Fan. During the last glacial maximum (LGM), especially in the late period, the Indian summer monsoon weakened, but the winter monsoon strengthened, resulting in a decrease in chemical weathering and elemental enrichment in the northeastern Indian Ocean. Conversely, when the rainfall was low, the chemical weathering strengthened and K 2 O/TiO 2 ratios were lowered due to the longer weathering time and resulting sediment potassium loss. However, when the sea level reached a certain height during the Holocene, the fluvial sediments could not easily enter deep-water environments through submarine channels, which were well developed in the Bengal Fan. Highlights • The major and trace elements of two cores were analyzed for sediment provenance. • The role of the Active Channel in the formation of the Bengal Fan was discussed. • The influence of the sea level fluctuations and rainfall changes over the past 50 ka was evaluated. • Coastal currents driven by the monsoon winds are key forces in sediment transport. [ABSTRACT FROM AUTHOR]

Deltas are important coastal sediment accumulation zones in both marine and lacustrine settings. However, currents derived from tides, waves or rivers can transfer that sediment into distal, deep environments, connecting terrestrial and deep marine depozones. The sediment transfer system of the Rhone River in Lake Geneva is composed of a sublacustrine delta, a deeply incised canyon and a distal lobe, which resembles, at a smaller scale, deep‐sea fan systems fed by high discharge rivers. From the comparison of two bathymetric datasets, collected in 1891 and 2014, a sediment budget was calculated for eastern Lake Geneva, based on which sediment distribution patterns were defined. During the past 125 years, sediment deposition occurred mostly in three high sedimentation rate areas: the proximal delta front, the canyon‐levée system and the distal lobe. Mean sedimentation rates in these areas vary from 0·0246 m year−1 (distal lobe) to 0·0737 m year−1 (delta front). Although the delta front–levées–distal lobe complex only comprises 17·0% of the analysed area, it stored 74·9% of the total deposited sediment. Results show that 52·5% of the total sediment stored in this complex was transported toward distal locations through the sublacustrine canyon. Namely, the canyon–levée complex stored 15·9% of the total sediment, while 36·6% was deposited in the distal lobe. The results thus show that in deltaic systems where density currents can occur regularly, a significant proportion of riverine sediment input may be transferred to the canyon‐lobe systems leading to important distal sediment accumulation zones. [ABSTRACT FROM AUTHOR]

Sandy sedimentary rocks rich in detrital matrix (>10% silt/clay) have long been recognized in the ancient sedimentary record, and nowhere more commonly than in deep‐marine turbidite systems. Despite this, their depositional mechanisms remain poorly understood, in part because these rocks, which are enriched in fine‐grained sediment, are often poorly exposed in outcrop or are confined to observation in core. Matrix‐rich strata in the Neoproterozoic Windermere Supergroup, in contrast, are very well‐exposed and show systematic changes in lithofacies over distances of several tens to a few hundreds of metres along‐strike. Notably, these strata are observed in both basin floor and continental slope deposits, suggesting that their occurrence and systematic lithological arrangement is related to mechanistic, rather than palaeogeographic, controls. Specifically, the facies transect consists of structureless, clayey sandstone that transforms along‐strike to a two‐layer deposit with the development of an upper, planar‐based, markedly more matrix‐rich layer. Further along‐strike, the basal clayey sandstone thins and eventually pinches out, leaving only the (upper) sandy claystone layer, which in turn thins along‐strike and then pinches out. These systematic changes in lithology, but more specifically the distribution of clay, is interpreted to form a depositional continuum related to particle settling in a horizontally advecting, high concentration particle suspension formed along the margins of an avulsion‐related high‐energy turbulent suspension. [ABSTRACT FROM AUTHOR]

• Both river and gobi sediments determined the sand provenance to the Badain Sand Sea. • The novel consensus ranking and consistent tracer selection methods were combined. • They allow identifying non-conservative and dissenting sediment tracers. • The spatial pattern of sediment contribution from different sources were outlined. • The Ejin gobi provides the main source contribution to the Badain Sand Sea. Fluvial and gobi sediments play significant roles in the formation of modern sand seas and their evolution. However, little is known about their respective source contributions, especially in quantitative terms. In the present study, we selected the Badain Jaran Sand Sea in Northwest China to quantitatively identify the sediment sources. To achieve this goal, we collected Heihe River sand and gobi sediments (Ejin gobi and the Beida–Yabrai gobis) as the potential sand sources. We performed provenance identification based on robust geochemical indicators, and found that both of these potential sources provided sand materials to the sand sea. Our quantitative analysis based on novel fingerprinting methods, namely consensus ranking (CR) and consistent tracer selection (CTS), suggested that the gobi sediments supplied more sand than the fluvial sand, accounting for 76.85 % and 23.15 % of the total (goodness of fit is 95.8 ± 3.89), respectively. Therein, the Ejin gobi was the dominant source for most regions of the sand sea (63.17 ± 21.43 %), but the Heihe River mainly fed sand source to the southern part of the sand sea (23.15 ± 18.66 %) and the Beida–Yabrai gobis provided the most sand to regions near the fan (13.68 ± 11.49 %). The source supply areas largely control above contribution difference. Our results demonstrate the critical role of gobi sediments for sand accumulation of the Badain Jaran Sand Sea. [ABSTRACT FROM AUTHOR]

Four decades of studies on pristine Baffin Island fjords are summarized with respect to sediment redistribution processes and resulting deposits. Sediment fill in these fjords occurred during the Holocene epoch, when deglacial and postglacial processes led to sandy-mud basin fills. The sand component mostly enters the fjord basins from fjordhead sandurs and their shoreline chute failures, triggering the release of yearly turbidity currents. These currents can travel long distances, often within leveed channels, leaving behind a seafloor of migrating cyclic steps that eventually transform into unconfined sediment waves. Channelized cyclic steps migrate upstream at up to tens of meters per year whereas unconfined finer-grained sediment waves migrate at much lower rates. Moored instruments and sediment traps in two fjords show turbidity currents to occur mostly in June through August when meltwater supply from glaciers is at a maximum. Not surprisingly, moored instruments were dragged downslope by turbidity current impact, suggesting high-concentration of suspended sediment within a thin near-bed layer. In rarer cases, large debris flows form even larger and longer submarine channels that carry sediment for tens of kilometers into the deep basin. These slide-generated debris flows can reorganize the basin floor as a sediment conduit for follow-on turbidity currents across thousands of years. Whereas sand is transferred to the deeper basin by turbidity currents, mud accumulates on the steep sidewall slopes and in the deep basin. Where mud accumulates on steep (≥13°) margins, many sidewall failures occur. Notably, right-hand margins contain a thicker sediment package and are affected by more sidewall failures than the left-hand side, primarily due to the Coriolis effect on increasing sediment accumulation rates. Of the many sidewall slope failures documented in Baffin Island fiords, iceberg collision with the seafloor is the only triggering mechanism directly observed. The association between subaerial debris flow fans and margin failures indicates that rock avalanches and subaerial debris flows also play a key role in triggering sidewall failures. The active seismic zone along Baffin Bay, likely initiated the rare but large deep-seated landslides observed in the sedimentary record. Baffin Island fjords are incredibly dynamic coastal environments with an ability to annually redistribute large masses of submarine sediment. • Sandur shorelines prograde slowly due to an average of ±65 shoreline chute failures generated every year per delta. • Turbidity currents create channelized cyclic steps, unconstrained cyclic step fields and sediment wave fields. • Fjord-margin sediment failures are common, where slopes exceed 13° and may be triggered by icebergs. • Massive failures, perhaps earthquake-related, reorganize seafloor transport along large submarine channels. • Within-layer sediment deformation is common where permeability between sediment layers is large. [ABSTRACT FROM AUTHOR]

Abstract: The Izumi Group in southwestern Japan is considered to represent deposits in a forearc basin along an active volcanic arc during the late Late Cretaceous. The group consists mainly of felsic volcanic and plutonic detritus, and overlies a Lower to Upper Cretaceous plutono‐metamorphic complex (the Ryoke complex). In order to reconstruct the depositional environments and constrain the age of deposition, sedimentary facies and U–Pb dating of zircon grains in tuff were studied for a drilled core obtained from the basal part of the Izumi Group. On the basis of the lithofacies associations, the core was subdivided into six units from base to top, as follows: mudstone‐dominated unit nonconformably deposited on the Ryoke granodiorite; tuffaceous mudstone‐dominated unit; tuff unit; tuffaceous sandstone–mudstone unit; sandstone–mudstone unit; and sandstone‐dominated unit. This succession suggests that the depositional system changed from non‐volcanic muddy slope or basin floor, to volcaniclastic sandy submarine fan. Based on a review of published radiometric age data of the surrounding region of the Ryoke complex and the Sanyo Belt which was an active volcanic front during deposition of the Izumi Group, the U–Pb age (82.7 ±0.5 Ma) of zircon grains in the tuff unit corresponds to those of felsic volcanic and pyroclastic rocks in the Sanyo Belt. [ABSTRACT FROM AUTHOR]

Hydrocarbons were analyzed in sediments from the Congo River deep-sea fan, from the Congo River, and in sinking particles collected by sediment traps 40 m above the sediment. Studied sites encompassed three lobes of decreasing age of formation along the canyon: sites A, F and C and a another lobe system, disconnected from the active channel since 4 ka, Site E. Terrestrial long-chain odd n -alkanes were dominant in all sediments of the lobe system. Unsaturated terpenoids sourced by higher plants, such as gammacerene, lupene, ursene and oleanene, were also detected. At site C, characterized by high accumulation rates (10–20 cm yr −1 ), the organic matter spends less time in the oxic layer than at other sites and high phytadiene concentrations 10–17 μg g OC −1 ) evidenced recent terrestrial and phytoplanktonic remains reworked in anaerobic conditions. In these sediments, organic carbon-normalized concentrations of terrestrial alkanes and terpenoids were several fold higher than in the lobe sediments with lower accumulation rates (sites A and F), arguing for a more rapid degradation of terrestrial hydrocarbons than bulk organic carbon in the first steps of pre-diagenesis. Ample variations in the contributions of biomarkers from higher plants, ferns, bacteria and angiosperms, indicate an heterogeneous contribution of the soil and vegetation detritus delivered to the Congo lobe sediments. Lower concentrations in terrestrial hydrocarbons at site E, 45 km away from the active canyon, indicated that river particles are still admixed to the dominant marine organic matter. Diploptene and hop-7(21)-ene have a dual origin, from terrestrial and marine microorganisms. Scatter in their relationship to gammacerene argues for a contribution of marine microorganisms, in addition to soils-sourced microorganisms. The close distribution patterns of diploptene, hop-21-ene, hop-7(21)ene and neohop-13(18)-ene is in line with the hypothesis of sequential clay-catalyzed isomerisation of bacterial hopenes. Terrestrial biomarker accumulation fluxes at site C are one order of magnitude higher than vertical pelagic flux, demonstrating the magnitude of the inputs delivered through turbiditic transport in the submarine canyon. Crude oil contamination was evidenced at the disconnected site E (UCM, C 21 to C 26 tricyclic diterpanes, CPI) and, in smaller amounts, in some sediments from sites A and C. It may be related to marine crude oil extraction and transport. A short-chain mode of alkanes with an even predominance is evidenced in sediments of the lobe complex and likely sources, crude oil, microorganisms and ferns, are discussed. [ABSTRACT FROM AUTHOR]

Geochemical profiles (SO 4 2- , H 2 S, CH 4 , δ 13 CH 4 ) and phylogenetic diversity of Archaea and Bacteria from two oceanographic cruises dedicated to the lobes sediments of the Congo deep-sea fan are presented in this paper. In this area, organic-rich turbidites reach 5000 m and allow the establishment of patchy cold-seep-like habitats including microbial mats, reduced sediments, and vesicomyid bivalves assemblages. These bivalves live in endosymbiosis with sulfur-oxidizing bacteria and use sulfides to perform chemosynthesis. In these habitats, unlike classical abyssal sediments, anoxic processes are dominant. Total oxygen uptake fluxes and methane fluxes measured with benthic chambers are in the same range as those of active cold-seep environments, and oxygen is mainly used for reoxidation of reduced compounds, especially in bacterial mats and reduced sediments. High concentrations of methane and sulfate co-exist in the upper 20 cm of sediments, and evidence indicates that sulfate-reducing microorganisms and methanogens co-occur in the shallow layers of these sediments. Simultaneously, anaerobic oxidation of methane (AOM) with sulfate as the electron acceptor is evidenced by the presence of ANMEs (ANaerobic MEthanotroph). Dissolved sulfide produced through the reduction of sulfate is reoxidized through several pathways depending on the habitat. These pathways include vesicomyid bivalves uptake (adults or juveniles in the bacterial mats habitats), reoxidation by oxygen or iron phases within the reduced sediment, or reoxidation by microbial mats. Sulfide uptake rates by vesicomyids measured in sulfide-rich sea water (90±18 mmol S m -2 d -1 ) were similar to sulfide production rates obtained by modelling the sulfate profile with different bioirrigation constants, highlighting the major control of vesicomyids on sulfur cycle in their habitats. [ABSTRACT FROM AUTHOR]

The Amazon submarine fan is a large sediment apron situated offshore Pará (Brazil) and represents the most distal extent of the Amazon River. The age of onset of this transcontinental river remains debated, yet is of great importance for understanding biotic evolutionary processes on land and at sea. Here we present new geochemical and palynological data from a borehole drilled at the continental slope and dated based on nannofossil biostratigraphy. We found that sediments of mixed source (craton and adjacent) occur at least from the late Oligocene (NP25) to late Miocene (NN9), and that the earliest Andes-derived sediments occur in NN10 (late Miocene). Our geochemical record indicates an onset of the transcontinental Amazon River between 9.4 and 9 Ma, which postdates the regional unconformity by 1 to 1.5 My. The shift in sediment geochemistry is more gradually replicated in the palynological record by a change from coastal plain and tropical lowland taxa to a mixture of tropical lowland, and montane forest to open Andean taxa. In particular, the appearance of taxa such as Jamesonia and Huperzia, followed by Valeriana , Polylepis-Acaena, Lysipomia and Plantago (with a current altitudinal range from 3200 to 4000 m) suggests the development of open, treeless, vegetation between 9.5 and 5.4 Ma, and highlight the presence of a high Andes in the late Miocene hinterland. Poaceae progressively increased from 9 Ma, with a notable rise from 4 Ma onwards, and percentages well above post-glacial and modern values, particularly between 2.6 and 0.8 Ma. We hypothesize that the rise of the grasses is a basin-wide phenomenon, but that the Plio-Pleistocene expansion of open, treeless vegetation on the Andean slopes and foothills are the main contributor. This rise in grasses was likely caused by climatic fluctuations, and subsequent changes in relief and erosion rates. We conclude that the onset of the Amazon River is coupled with Neogene Andean tectonism and that subsequent developments, both of river and biota, are closely linked to the Plio-Pleistocene climatic fluctuations. From latest Neogene onwards these major landscape changes determined the composition of the montane and lowland forest in the Andes-Amazonian system. [ABSTRACT FROM AUTHOR]

Effective seal breaching is a major contributor to methane seepage from deep sea sediments as it ensures the migration of gas and liquid hydrocarbons from buried reservoirs to the seafloor. This study shows two giant pockmarks on the lower slope of the Lower Congo Basin associated with salt-tectonic faulting and the buried Pliocene Congo deep sea fan. The progressive burial of Pliocene fan deposits results in mobilization of methane from gas hydrates at the Base of the Gas Hydrate Stability Zone which migrates through the hemipelagic seal towards the seafloor along salt-induced faults. Seal-breaching in this part of the Lower Congo Basin relies solely on salt-tectonic faulting contrasting with upslope seafloor seepage settings where polygonal faulting within the hemipelagic seal occurs. Dedicated 2D and 3D seismic and acoustic surveying allows the detailed reconstruction of the evolution of pockmarks which appear to have been active for the last 640 kyr. We also show indications that the modern seafloor depression formed due to reduced sedimentation in the vicinity of active seepage. The presented seafloor seepage features illustrate the mode of gas release from the Pliocene fan in the Lower Congo Basin, which contrasts with previously investigated seepage environments further upslope. [ABSTRACT FROM AUTHOR]

The response of continental-scale drainage systems to short-term (i.e., millennial-scale) climate change is unknown but has wide implications for understanding climate feedbacks and terrestrial-marine fluxes. The late Wisconsin Mississippi River to deep-sea fan of North America was one of Earth's largest sediment-routing networks during the most recent glacioeustatic cycle. To understand late Pleistocene sediment production and dispersal related to the partly glaciated, ancestral Mississippi system, we sampled late Wisconsin deep-sea fan channel-fill and lobe deposits for detrital zircon U-Pb and (U-Th)/He double-dating analyses, from Deep Sea Drilling Project (Leg 96) cores and U.S. Geological Survey piston cores. Our results suggest a late Pleistocene glacial Mississippi system that forced a larger transfer of sediment from Cordilleran magmatic provinces and the Canadian Shield when compared to the modern drainage. This indicates a potentially more expansive and/or erosive ancestral Mississippi catchment, and the efficient dispersal of terrigenous sediment, nutrients, and solutes into the deep-sea via high-discharge meltwater and glacial-lake outbursts during ice retreat. [ABSTRACT FROM AUTHOR]

The sediment succession in the Bay of Bengal (BoB) records the signatures corresponding to India-Asia collision, regional climate change, and erosional processes of both the Himalayan orogen and Indian subcontinent. The Bengal Fan - the world's largest submarine fan - has long been studied to understand the link between the Himalayan tectonics and Asian monsoon. But, lack of detailed information on corresponding signals hampered the understanding of related processes of tectonics, climate and erosion. The present study of long-streamer seismic reflection profile data and information from deep drill well logs in the western BoB has revealed two different phases of sediment deposition. In the first phase, until Oligocene- Miocene (∼23 Ma), Indian peninsular rivers discharged sediments to the BoB which accumulated at a rate ∼20 m/m.y. with an aberration of twofairly enhanced sediment pulses during the periods from 65 to 54 Ma and 34 to 23 Ma. In the second phase, since 23 Ma, the Ganges and Brahmaputra rivers added huge volumes of sediments to the bay at variable rates ranging from 40 to >1000 m/m.y. A distinct increase in sediment discharge (∼140 m/m.y.) during the Oligocene- Miocene (∼23 Ma) together with the development of regional onlap unconformity and the start of turbidity system provide an important age marker corresponding to rapid exhumation of the Himalaya, which intensified the erosional process and commencement of Bengal Fan sedimentation. Further rise in the rate of sedimentation during the period 6.8-0.8 Ma is coincident with the change in monsoon intensity, but surprisingly not in agreement with the decrease in sediment rate reported at ODP Leg 116 sites in the distal Bengal Fan. Here we provide wellconstrained ages for the commencement and growth of the Bengal Fan, which can serve as benchmark information for understanding the interaction between the Himalayan exhumation and Asian climate. [ABSTRACT FROM AUTHOR]

The source-to-sink (S2S) concept is focused on quantification of the various components of siliciclastic sedimentary systems from initial source sediment production areas, through the dispersal system, to deposition within a number of potential ultimate sedimentary sinks, and has more recently been applied to deep-time stratigraphic systems. Sequence-stratigraphic analysis is a key first step that allows depositional systems to be correlated and mapped, within a time-stratigraphic framework, such that fluvial transport systems can be linked to down-dip shorelines, shelf and deep-water deposits and interpreted in the context of allogenic processes. More recently, attempts have been made to quantify catchment areas for ancient depositional systems, using scaling relationships of modern systems. This also helps predict the size of linked depositional systems, such as rivers, deltas and submarine fans, along the S2S tract. The maximum size of any given depositional system, such as a river, delta, or submarine fan, is significantly controlled by the area, relief, and climate regime of the source area, which in turn may link to the plate tectonic and paleogeographic setting. Classic provenance studies, and more recent use of detrital geochronology, including zircons, provide critical information about source areas, and place limits on catchment area. Provenance studies, especially when linked to thermochronometry also provide key information about rates of exhumation of source areas and the link to the tectonic setting. In this paper the techniques for estimation of water and sediment paleodischarge and paleo-drainage area are outlined, and sediment budgets are calculated for a number of Mesozoic systems, primarily from western North America. The relevance for hydrocarbon exploration and production is discussed for each example. In Mesozoic Western Interior basins of North America, extensive outcrop and subsurface data allow the largest trunk rivers to be identified, typically within incised valleys. Thickness, grain size, and sedimentary structures can be used to infer slope and flow velocities, and using width estimations, water and sediment paleodischarge can be calculated. River paleoslope can also be independently measured from stratigraphic-geometric considerations and used to assess paleo-river flow. Paleodischarge in turn is used to estimate the size of the catchment source area. Paleodischarge of rivers can also be estimated independently by integrating estimates of catchment source area, for example by using detrital zircons integrated with paleoclimate. The catchment areas of North America evolved significantly during the late Mesozoic. During the Jurassic–Early Cretaceous, fluvial systems consisted of continental-scale low slope (S = 10 − 4 ), axially drained rivers, forming the 40-m-deep channels in the Mannville Group in Canada, which now host the supergiant heavy-oil-sands reserves. During the times of maximum transgression of the Cretaceous Seaway, such as the Turonian and Campanian, the western North American foreland basin was characterized by smaller-scale (typically 10-m deep), steeper gradient (S = 10 − 3 ) sand and gravel bedload rivers, dominated by transverse drainages in the rising Cordillera. This created a number of smaller river-delta S2S systems along the coast. As the Laramide Orogeny progressed, the Western Interior Seaway receded, and by the Paleocene the modern continental-scale drainage of North America was largely established with a major continental division separating south-flowing Mississippi drainages from north-flowing systems. The integration of paleodischarge estimates with provenance analysis enables the improved use of the sedimentary record to make estimates about the entire S2S system, as opposed to primarily the depositional component. Clinothem stacking relationships and isopach mapping of stratigraphic volumes have also been integrated with chronostratigraphic data to analyze long-term S2S sediment budgets. A more quantitative approach to estimating the scale of erosional, transport and depositional components of sedimentary systems, especially in the context of linked source and depositional areas, also puts constraints on the size and scale of potential hydrocarbon reservoirs and thus has significant economic value. [ABSTRACT FROM AUTHOR]

The lithostratigraphic plays in the Dongfang area of the Yinggehai Basin at the northern margin of the South China Sea consist of a Neogene multistage, thinly bedded, channel-lobe system. Integrating high-resolution 3D seismic, lithological and well log data shows that the channel-lobe system developed primarily in the lowstand system tract of the Huangliu Formation. We investigated the developmental stages of lobes based on the stacking relationships of seismic events, the degrees of channel downcutting in lobes, and the occurrences of sandstone facies observed in the stratal slices. The lobes finally identified 9 small-scale stages, which reveal a complete sedimentary cycle controlled by high-frequency sea-level fluctuations. Facies architectures such as main channels, channels and overbank deposits were identified by using seismic sedimentology and geomorphology. Seismic stratal slices display the different characteristics of the sediment dispersal patterns in the northern part (block DF-a) and the southern region (block DF-b). The northern part contains isolated lobes. The southern region mostly contains deeply incised channels and meander belts that are wider than those in the northern part. Three main sediment dispersal patterns have been recognized, namely, channel-lobe, channelized lobe and non-channelized lobe. Sea level fluctuation and topographic variations exert strong influences on spatial-temporal evolution of the sediment diffusion and are the key controlling factors for the patterns. The methodology used in this study characterizes the submarine fan development in an area with limited well control; this methodology is more accurate for reservoir-scale exploration and development compared to other uses. • The standardized process of the stage analysis of different scales in the channel-lobe system. • Integrated with seismic, lithology, and well logging data to identify sediment-dispersal patterns in the channel-lobe system. • This study reveals a complete cycle transformation and key control factors within a high-resolution sequence. • This work can serve as a useful reference for sediment-dispersal patterns distinguish and stage analysis. [ABSTRACT FROM AUTHOR]

• First monitoring of sediment transfer in submarine channel from source to sink. • River input and lobe aggradation approximately balances over decadal timescales. • Most turbidity currents deposit within the proximal part of the channel. • Infrequent large flows flush the channel; transporting sediment onto the lobe. • Flushing events can occur without obvious triggers, and can be internally generated. Submarine channels are the primary conduits for land-derived material, including organic carbon, pollutants, and nutrients, into the deep-sea. The flows (turbidity currents) that traverse these systems can pose hazards to seafloor infrastructure such as cables and pipelines. Here we use a novel combination of repeat seafloor surveys and turbidity current monitoring along a 50 km-long submarine channel in Bute Inlet, British Columbia, and discharge measurements from the main feeding river. These source-to-sink observations provide the most detailed information yet on magnitude-frequency-distance relationships for turbidity currents, and the spatial-temporal patterns of sediment transport within a submarine channel-lobe system. This analysis provides new insights into mass redistribution, and particle residence times in submarine channels, as well as where particles are eventually buried and how that is recorded in the deposits. We observe stepwise sediment transport down the channel, with turbidity currents becoming progressively less frequent with distance. Most flows dissipate and deposit within the proximal (< 11 km) part of the system, whilst longer run-out flows then pick up this sediment, 'shuffling' it further downstream along the channel. This shuffling occurs mainly through upstream migration of knickpoints, which can generate sediment bypass along the channel over timescales of 10–100 yrs. Infrequent large events flush the channel and ultimately transport sediment onto the lobe. These flushing events can occur without obvious triggers, and thus might be internally generated. We then present the first ever sediment budget analysis of an entire submarine channel system, which shows that the river input and lobe aggradation can approximately balance over decadal timescales. We conclude by discussing the implication of this sediment shuffling for seafloor geohazards and particle burial. [ABSTRACT FROM AUTHOR]

A comprehensive analysis of small deltaic environments linked to short, mountainous, and seasonal fluvial systems in the northern shelf of the Alboran Sea was undertaken in order to define the controlling parameters of the geomorphological variability. The database includes multibeam and backscatter imagery, surficial sediment samples, and high-resolution seismic profiles. Additionally, geomorphological and hydrodynamic modeling and statistical analysis (principal component and cluster analysis) of hydrological and physiographic variables were performed. Most of the studied deltaic systems have high-gradient, coarse-grained deposits with preferential development of the submarine portions to the detriment of the deltaic plains. The geomorphological analysis identified three basic types of plan-view distributions according to the length-to-width ratios: elongate, linguoid and lobate. Cross-slope profiles evidence dominant concave-upward geometries, fewer occurrences of planar geometries, and no sigmoid profiles. Sediment depocenters are extremely thick in proximal locations, but thin out rapidly seawards. The geometric distribution patterns of the deltaic systems are characterized by a predictable pattern in plan-view according to the type of fluvial system, ranging from a relatively large river to ephemeral creeks. Prevailing concave and secondary planar profiles support strong sediment progradation in the submarine realm and low sediment retention in the emerged deltaic environment. Two different types of systems are distinguished: (1) larger rivers, where deltaic deposition is largely controlled by basin dimensions, ultimately dictating the magnitude of water and sediment discharges; and (2) smaller rivers and creeks, where deltaic geometries are related to the basin slopes. The influence of hydrodynamic variables on defining the submarine deltaic geometry has been observed in the case of concave-upward geometries, where geomorphological boundaries are defined by medium- and high-energy wave conditions. [ABSTRACT FROM AUTHOR]

Abstract: Subaqueous sediment density flows are one of the volumetrically most important processes for moving sediment across our planet, and form the largest sediment accumulations on Earth (submarine fans). They are also arguably the most sparely monitored major sediment transport processes on our planet. Significant advances have been made in documenting their timing and triggers, especially within submarine canyons and delta-fronts, and freshwater lakes and reservoirs, but the sediment concentration of flows that run out beyond the continental slope has never been measured directly. This limited amount of monitoring data contrasts sharply with other major types of sediment flow, such as river systems, and ensure that understanding submarine sediment density flows remains a major challenge for Earth science. The available monitoring data define a series of flow types whose character and deposits differ significantly. Large (>100km3) failures on the continental slope can generate fast-moving (up to 19m/s) flows that reach the deep ocean, and deposit thick layers of sand across submarine fans. Even small volume (0.008km3) canyon head failures can sometimes generate channelised flows that travel at >5m/s for several hundred kilometres. A single event off SE Taiwan shows that river floods can generate powerful flows that reach the deep ocean, in this case triggered by failure of recently deposited sediment in the canyon head. Direct monitoring evidence of powerful oceanic flows produced by plunging hyperpycnal flood water is lacking, although this process has produced shorter and weaker oceanic flows. Numerous flows can occur each year on river-fed delta fronts, where they can generate up-slope migrating crescentic bedforms. These flows tend to occur during the flood season, but are not necessarily associated with individual flood discharge peaks, suggesting that they are often triggered by delta-front slope failures. Powerful flows occur several times each year in canyons fed by sand from the shelf, associated with strong wave action. These flows can also generate up-slope migrating crescentic bedforms that most likely originate due to retrogressive breaching associated with a dense near-bed layer of sediment. Expanded dilute flows that are supercritical and fully turbulent are also triggered by wave action in canyons. Sediment density flows in lakes and reservoirs generated by plunging river flood water have been monitored in much greater detail. They are typically very dilute (<0.01vol.% sediment) and travel at <50cm/s, and are prone to generating interflows within the density stratified freshwater. A key objective for future work is to develop measurement techniques for seeing through overlying dilute clouds of sediment, to determine whether dense near-bed layers are present. There is also a need to combine monitoring of flows with detailed analyses of flow deposits, in order to understand how flows are recorded in the rock record. Finally, a source-to-sink approach is needed because the character of submarine flows can change significantly along their flow path. [Copyright &y& Elsevier]

The Tonya Formation, which represents the uppermost part of the Mesozoic sequence in the Eastern Pontides, consists of calciturbidites in Trabzon and its surrounding region. Two stratigraphic sections of the unit were measured in the Hacımehmet and Gürbulak areas to decipher the distribution of rock types, facies architecture, sediment textures and depositional environment. The grain size, channels, suprafan lobes and slump structures of the sediments suggest that calciclastic sequences were deposited in a submarine fan system. Calcarenites/calcirudites and hemipelagic rocks, comprising an alternation of marls and mudstones, are the two dominant lithologies described in the studied calciclastic submarine fan system. Calciclastic facies, which are identified as middle fan deposits, indicate high-concentration turbidity currents in the sequences. The hemipelagic rocks, which are delineated as outer fan deposits, suggest low-energy, deep-marine conditions. The microfacies description and fauna determinations propose the gravity origin for these calciclastic submarine fan deposits. Rudstones, grainstones and packstones are the dominant carbonate textures in the calcarenites. Pelagic marls and mudstones are characterised by a planktonic, foraminifera-bearing, wackestone-mudstone texture. Biogene parts of the calciclastics are fragments of benthonic foraminifers, algae, rudists, echinoids, bryozoa, inoceramids and neritic and pelagic carbonate lithoclasts, which suggest a close contemporaneous shallow marine carbonate depositional environment as their source during their deposition. Palaeocurrent directions, measured from the base of the calciturbidites, show that the components of the calciturbidites were transported from a shallow marine environment lying to the E or SE. The lateral and vertical facies organisation of these calciturbidites favours a deposition of the calciclastic submarine fan model. These deposits were fed by material derived from a shallower water carbonate depositional environment in the Eastern Pontides during the Late Campanian. All the sedimentological properties, combined with the regional data, suggest that the Late Campanian sedimentation in the Eastern Pontides formed in a backarc environment. [ABSTRACT FROM AUTHOR]

Low-grade metamorphosed Cretaceous sedimentary records of forearc basin systems in the eastern part of the Transhimalaya (Gangdese) arc system have not been reported yet, impairing understanding of the Mesozoic-Cenozoic convergent margin processes along the southern margin of Asia. This study incorporates observations from petrography, stratigraphy, sedimentology, and analyses of detrital-zircon geochronology and bulk-rock Sr-Nd isotope for a series of low-grade metamorphosed sedimentary rocks referred to as the Lilong succession in the eastern Yarlung Zangbo suture zone, east of Langxian, in southeastern Tibet, China. Field observations reveal that this unit has three different lithological associations (I, II, and III) including gravel-coarse sandy inner-middle submarine fan facies, sandy-muddy middle-outer submarine fan facies, and silty-muddy outer submarine fan and/or deep sea plain facies moving higher in the succession. Detrital-zircon geochronology indicates a maximum depositional age of ~110 Ma and the absence of younger zircons that are dominant in the Gangdese batholith north of the basin suggests the minimum depositional age ~ 85 Ma, comprising an interval of the Albian-Santonian age. Volcanic and granitic clasts in sandstones/conglomerates, ε Nd (0) values (−0.09 and 4.6) and 87Sr/86Sr ratios (0.704105–0.704770) of slates, and detrital zircon age spectra (mainly 100–140 Ma) demonstrate provenance from the central-northern and southern Lhasa Terrane. In addition, there is evidence for recycling of cherty beds of the Chongdui Formation. Similarities between provenance, lithofacies, and tectonic setting lead us to interpret that the newly identified remnant unit correlates to the Ngamring Formation in the Xigaze forearc basin. When taking into account the lower Bomi Group and Nyingchi complex, we propose that the Lilong succession and the metamorphosed composite in the eastern Himalayan syntaxis are counterpart remnants of the eastern Xigaze forearc basin system, which are different from the two forearc basin systems in the western Himalaya. • The Albian-Santonian Lilong succession identified near the E Himalaya syntaxis • The Lilong succession deposited in a submarine fan system • The Lilong succession developed in a forearc basin with sources of Lhasa Terrane • Forearc basin system in central and E Himalaya differs from that in W Himalaya [ABSTRACT FROM AUTHOR]