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Grain size distributions of high- and low-density grains for one sample from the density experiment (sample x = 2700, y = 2000; location of the sample shown in ). (b) Calculated ws distributions for the same sample.
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[1] This study uses measurements from physical experiments to document turbidity currents, which are density currents composed of suspended sediment and water, to be effective at hydrodynamically fractionating minerals on the basis of grain density and grain shape alone, resulting in large-scale spatial variations in the composition of their deposi...
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... Flow conditions included the type of flow, flow velocity, and bottom stresses, and these were found for different stages within the Bouma sequence. Pyles et al. (2013) performed physical experiments at the lab-scale with low-density turbidity currents composed of artificial particle mixtures and found that while being spatially fractionated, the samples at any one location were in hydrodynamic equivalence. ...
Heavy‐mineral suites are used widely in sandstone provenance and are key when connecting source and sink. When characterizing provenance related signatures, it is essential to understand the different factors that may influence a particular heavy‐mineral assemblage for example, chemical weathering or diagenetic processes. Hydrodynamics, causing size‐density sorting, exert major control on the distribution of heavy minerals. Here, we highlight the effect of grain‐size inheritance, essentially the absence of certain grain sizes within a specific heavy‐mineral species, on two distinct types of sediments. Modern deposits from a high‐energy beach in NW Denmark give an analog for heavily reworked sediment, primarily controlled by hydrodynamic processes. In contrast, three Palaeogene turbidite successions in the Eastern Alps were sampled, presenting a more complex history that includes diagenesis. All samples were processed for their heavy‐mineral compositions using Raman spectroscopy, and several techniques applied to determine the effect of grain‐size inheritance. Results show that (a) even within the hydrodynamically well‐sorted beach and placer deposits, evidence of grain‐size inheritance is apparent, and (b) turbidites of variable heavy‐mineral composition show strong effects of grain‐size inheritance for several mineral species. Moreover, considerable intersample contrasts within single turbidite beds are observed. We enforce the importance of understanding grain‐size inheritance, as well as other processes effecting size‐density relations in clastic sediment that go well beyond purely hydrodynamic control of intrasample heavy‐mineral variability.
... River mouths are the dynamic dispersal sites of riverine sediments (Coleman and Wright, 1975). Sediment flows across river mouths spatially segregate their sediment load according to density, shape, and size of the grains (Choux and Druitt, 2002;Hodson and Alexander, 2010;Luthi, 1981;Mériaux and Kurz-Besson, 2017;Pyles et al., 2013); sediment laden flows carry, entrain or deposit grains depending on their type and grainsupport mechanisms, which vary spatially and temporally (Baas et al., 2011;Fildani et al., 2018;Kane et al., 2017;Stevenson et al., 2014;Talling et al., 2012). Despite the recognition of deltas as extremely dynamic environments, we have a limited ability to predict MPs concentrations in distinctive sectors of a delta and particularly so for their subenvironments in subaqueous prodeltas. ...
Deltas are the locus of river-borne sediment accumulation, however, their role in sequestering plastic pollutants is still overlooked. By combining geomorphological, sedimentological, and geochemical analyses, which include time-lapse multibeam bathymetry, sediment provenance, and μFT-IR analyses, we investigate the fate of plastic particles after a river flood event providing an unprecedented documentation of the spatial distribution of sediment as well as of microplastics (MPs), including particles fibers, and phthalates (PAEs) abundances in the subaqueous delta. Overall sediments are characterized by an average of 139.7 ± 80 MPs/kg d.w., but display spatial heterogeneity of sediment and MPs accumulation: MPs are absent within the active sandy delta lobe, reflecting dilution by clastic sediment (ca. 1.3 Mm3) and sediment bypass. The highest MP concentration (625 MPs/kg d.w.) occurs in the distal reaches of the active lobe where flow energy dissipates. In addition to MPs, cellulosic fibers are relevant (of up to 3800 fibers/kg d.w.) in all the analyzed sediment samples, and dominate (94 %) with respect to synthetic polymers. Statistically significant differences in the relative concentration of fiber fragments ≤0.5 mm in size were highlighted between the active delta lobe and the migrating bedforms in the prodelta. Fibers were found to slightly follow a power law size distribution coherent with a one-dimensional fragmentation model and thus indicating the absence of a size dependent selection mechanism during burial. Multivariate statistical analysis suggests traveling distance and bottom-transport regime as the most relevant factors controlling particle distribution. Our findings suggest that subaqueous prodelta should be considered hot spots for the accumulation of MPs and associated pollutants, albeit the strong lateral heterogeneity in their abundances reflects changes in the relative influence of fluvial and marine processes.
... Because particles in turbidity currents attain differential settling velocities, grains reach the bed at different positions along the turbidity current's path (Bornhold & Pilkey, 1971;Stammer, 2014). As a consequence of this longitudinal sorting mechanism, proximal turbidites are enriched in grains with higher settling velocities and grade distally into deposits dominated by particles with lower settling velocities (Pyles et al., 2013;Counts et al., 2021;Le Goff et al., 2021). This trend is also evident in vertical cross-sections of deposits, because at a fixed point on the bed faster-settling grains reach the bed before slower ones (Fig. 1). ...
... These concepts have been extensively explored for siliciclastic turbidites (e.g. van Tassell, 1981;Kneller & McCaffrey, 2003;Talling et al., 2007;Pyles et al., 2013), but have received little attention for turbidites of carbonate composition (Hodson & Alexander, 2010). In turbidity currents transporting quartz grains, the highest settling velocities are reached by coarser particles, while finer grains with lower settling velocities remain in suspension for longer; forming a fining-upward succession when they eventually are deposited (Kuenen & Migliorini, 1950). ...
... Choux & Druitt (2002) and Hodson & Alexander (2010) focused on densitysegregation processes in two dimensions. Pyles et al. (2013), on the other hand, experimentally investigated the effect of particle density in turbidity currents on the distribution of grain properties in submarine lobes (see also Stammer, 2014). They found that high-density particles are deposited predominantly in the axis of the lobe, and that particle density decreased longitudinally and laterally to the lobe fringes. ...
Particle transport and deposition in turbidity currents is governed by the balance between turbulent suspension and gravitational settling, with settling velocity becoming dominant during the final rain‐out phases of decelerated turbidity currents on lobes. Differential particle settling velocities play a role in the sorting of grains in turbidity currents; there is a preference of grains with higher settling velocities to be deposited first, yielding a settling‐velocity gradient in vertical and longitudinal cross‐sections through turbidite beds. If sediments contain little variation in particle shape and density (for example, siliciclastics), then settling velocity is dominantly controlled by grain size. Carbonate sediments, in contrast, are composed of non‐skeletal and skeletal grains with various growth structures, producing a wide distribution of particle shapes (from spheroidal to platy, bladed and elongated forms). The present paper aims to constrain the extent to which shape‐dependent differential settling velocities influence sorting mechanisms in carbonate turbidity currents. Experiments using natural skeletal sand were conducted to investigate the settling of carbonate grains in: (i) isolation; (ii) suspension clouds; and (iii) turbidity currents. Size, density and shape parameters, including Corey Shape Factor and Zingg diagrams, were analysed using high‐resolution micro‐computed tomography. The slower settling of non‐spheroidal shapes was quantified. In the sinking suspensions, a sorting mechanism operated through differential velocities yielding an abundance of spheroidal grains at the base and enrichment in less‐spheroidal grains towards the top of suspension deposits. This trend was also observed longitudinally in carbonate turbidity currents, for which enhanced advection lengths caused less spheroidal grains to be transported farther into the basin. The effect of particle shape becomes increasingly significant as grain size increases, in particular above medium sand. Carbonate turbidites may therefore be more poorly sorted than siliciclastic turbidites, which is expected to result in lower primary porosity in calciturbidites compared to siliciclastic turbidites.
... It is unclear why this sandstone, and the sandy matrix to the conglomerate at the base of S2b, are petrographically distinct from their overlying sandbodies. It could reflect slightly different terranes being tapped as their respective depositional systems establish themselves or result from hydrodynamic fractionation processes along the evolving sediment transport pathways (Pyles et al. 2013). ...
... This wider context supports the lobe-dominated origin for the S1b Lower succession, and also indicates they represent terminal deposits fed broadly from the north. The latter point is significant because it provides an explanation for the high abundance of mica, organic matter and detrital fines, as these have low settling velocities due to their size and/or density and/or shape (Pye 1994) and are prone to hydrodynamic fractionation that results in deposition at the distal end of sediment transport paths (Pyles et al. 2013). Such processes are also likely to be responsible for the presence of the original volcanic grains that through subsequent alteration resulted in the abundant pseudomatrix within the S1b Lower deposits. ...
Quad 29 in the Central North Sea is a focus for bp, with a strategy to identify remaining hydrocarbon accumulations to tieback to existing infrastructure. Capercaillie was appraised in 2017 with well 29/04e-5 and sidetrack 29/04e-5z. A gas cap and thin oil rim were intersected within the siliciclastic Palaeocene-Eocene Sele Formation. The reservoir sandstones were deposited in a deep marine setting by sediment gravity flow processes. Within the context of a relatively detailed knowledge of the surrounding area, the reservoir data-operational risk-cost balance was addressed through acquisition of a full wireline logging suite, pressure data, latest-generation microresistivity images and targeted large-volume rotary sidewall cores, with the latter two favoured over whole core.
Mature deepwater descriptive schemes were applied at the sidewall core (lithotype), bed (borehole image facies) and bed-stack (depositional package) scales. This hierarchical approach provided robust sedimentological data to underpin higher-order depositional models, which together were used as a framework to: 1) constrain the reservoirs' mineralogical and textural attributes, 2) establish the main controls on rock quality, 3) explain the resulting variations in porosity and permeability.
This study demonstrates that the careful integration of data derived from the latest borehole imaging tools and large-volume RSWCs can be a successful means of characterising reservoirs from a sedimentological, reservoir quality and reservoir architecture perspective in mature basins. Similar approaches to geological reservoir characterisation in such settings are likely to be a common cornerstone of cost-effective development during the energy transition.
Supplementary material at https://doi.org/10.6084/m9.figshare.c.6444408
... In other words, the majority of HEBs described herein reflect the down-dip equivalent of slope failures (for example, HEB-1, HEB-2 and HEB9 in Pierce et al., 2018). Various mechanisms have been proposed to explain the origin of hybrid event beds in deep-water depositional systems, including: (i) slope instability with rapid entrainment of large amounts of mud-rich material and the generation of a slump or debris flow (Talling et al., 2004;Haughton et al., 2009;Pierce et al., 2018); (ii) "partial transformation from a debris flow due to continued runout of flow and the development of a forerunner turbidity current" (Haughton et al., 2003;Talling et al., 2007); (iii) longitudinal and lateral transformation from turbidity current (non-cohesive) to debris flow (cohesive) promoted by incorporation of significant clay and mudstone clasts into the flow by seafloor erosion (flow bulking) (Talling et al., 2004(Talling et al., , 2007Haughton et al., 2009;Pyles et al., 2013;Fonnesu et al., 2016;Pierce et al., 2018); and (iv) turbulence dampening and transformation from turbidity current to debris flow due to decreases in axial gradient and flow expansion (Talling et al., 2007). ...
The distribution of conventional subichnofacies in deep‐water fan systems (i.e. Ophiomorpha rudis–Paleodictyon–Nereites‐subichnofacies) depends on the presence of fully turbulent non‐cohesive flows such as low‐density turbidites and high‐density turbidites. However, changes in flow state between laminar and turbulent conditions can affect the distribution style of conventional subichnofacies. This study deals with the effects of environmental or ecological stressors as a result of hybrid sediment gravity flows (HEB) on distribution and composition of trace fossils in deep‐marine depositional system of the Ordovician Ghelli Formation in the north‐eastern Alborz. The spatial distribution and sedimentological character of hybrid sediment gravity flows, in particular their abundance in the down‐dip parts of lobe‐related facies associations, are interpreted as products of longitudinal and lateral transformation from turbidity currents to debris‐flows promoted by incorporation of significant claystone and mudstone clasts into the flow by seafloor erosion and flow bulking. Seven trace‐fossil assemblages were recognized in the channel and lobe‐related facies associations. The observed spatial distribution of trace‐fossil assemblages in the interpreted frontal and lateral lobe fringes, somewhat contrasts with conventional subichnofacies distribution models. The development of cohesive flows and rapid emplacement of turbidite, banded and debrite beds could be accompanied by fluctuations in physico‐chemical conditions and, hence, the time available for colonization and the lifestyle of producers. This study suggests that compared to the archetypal models of the subichnofacies in down‐dip parts of lobe‐related facies associations, ichnodiversity and density of bioturbation are drastically reduced, and trace fossils are limited to simple, shallow‐tier feeding strategies. Commonly, the presence of cohesive flows may have forced the producers in the Paleodictyon and Nereites‐subichnofacies to migrate into lateral lobe fringe with more participation of low‐density turbidites. This study shows that, in addition to sedimentological and architectural criteria, ichnological criteria can also be used to distinguish between frontal and lateral lobe‐fringe deposits in unconfined systems.
... Consequently, a depositing sediment gravity flow may have zones that remain fully turbulent, typically towards the front and core of the flow, and other areas where the turbulence is completely or at least partly dampened. As these flows have a largely turbulent transport phase prior to transformation, they have the capability to sort and segregate components on the basis of particle size, shape and density (Pyles et al., 2013;Marchand et al., 2015). Components that segregate together with mud, specifically micas and organic matter, can become enriched in a part of the flow that subsequently transforms to a laminar rheology ahead of deposition (Haughton et al., 2003;Hussain et al., 2020Hussain et al., , 2021. ...
... A second set of models stressed the 'longitudinal segregation' of flows ( Fig. 5b; Haughton et al., 2009) in which the fractionation (lateral or longitudinal) of mud and associated particles of mica and organic matter (Stanley, 1986;Pyles et al., 2013) create regions of the flow that have transitional and then quasi-laminar flow characteristics (Baas et al., 2009;Haughton et al., 2009). Under these conditions, the aggrading deposit records different areas of the flow as it passes, with clean sand (H1) deposited from the turbulent flow front and muddy sandstones (H3) from the tail of the flow. ...
... Sedimentation and fluidization are two important areas where understanding the superficial velocity is essential. For sedimentation, the reduced settling velocity of particles in a fluid is a critical physical parameter [3]. Baas et al. [4] reviewed experimental data sets of sediment settling velocity in the literature and proposed new empirical equations for a wide range of particle size and density, liquid density, and viscosity. ...
The interplay of particles in a heterogeneous multiparticle two-phase system and its effect on superficial velocity have not been well quantified. In this study, a new model is developed to examine the superficial velocity in a heterogeneous multiparticle two-phase system. To examine the heterogeneous effects to the potentially maximum extent, the particle concentration is assumed to follow a truncated fractal distribution, which is integrated into the free surface cell model. In a statistical sense, the multiparticle two-phase system is stationary, so the mean of spatial heterogeneity can be replaced by the ensemble mean. Since the underlying physical concept is rooted in the free surface cell model, the validity of the model should be, therefore, limited to the low-Reynolds number conditions. The developed model is compared to data from three representative experimental studies in the literature and it is found that the model can better capture the scatters in experimental data than the original free surface cell model. The model is also compared with three representative models and demonstrates reasonable results. While the deterministic free surface cell model underestimates the velocity, the cell model with truncated fractal distribution being incorporated can predict high velocity with a wide range of particle concentration heterogeneity.
... With reference to the mixed siliciclastic-carbonate deposits, texture of these deposits is also linked to hydrodynamic flow processes, which dictate segregation of skeletal and clastic grains. The capacity of mineral grains to respond to the main hydrodynamic processes is strictly dependent upon their own physical properties such as shape and density (McNeill et al., 2004;Pyles et al., 2013;Marchand et al., 2015;Chiarella et al., 2017). It is an important process because primary and secondary porosity can be controlled by the amount of carbonate grains mixed with their siliciclastic counterparts (Mansurbeg et al., 2009;Feng et al., 2013). ...
The Miocene, syn-rift mixed siliciclastic-carbonate strata has been a long sought-after reservoir objective in the Red Sea rift basins. Despite being viable prospects, their depositional architecture, mechanisms of siliciclastics and carbonate mixing, and fundamental controls on their reservoir quality remained elusive and enigmatic. In this study, we used sedimentological, petrographical and outcrop permeametry measurements to investigate the stratigraphic record and reservoir quality of mixed siliciclastic-carbonate deposits. The latter are preserved at the transition between non-marine Al-Wajh Formation and marine carbonates of the Musayr Formation in one of the Red sea rift basins, NW Saudi Arabia. Three major facies associations were identified using detailed logging facies analysis, including siliciclastic-rich, mixed siliciclastic-carbonate and carbonate-rich facies association. These facies associations, represent a basinward transition from dominantly non-marine alluvial fans, braided streams and shallow-water delta into an open marine carbonate ramp. The permeability of siliciclastic facies is orders of magnitude higher (average permeability = 1884 md) than mixed siliciclastic-carbonate (average permeability = 109 md) and carbonate (average permeability = 46 md) facies. Likewise, siliciclastic facies have higher porosity (average porosity = 17%) compared to mixed (average porosity = 7%), and carbonate (average porosity = 15%) deposits. Petrographic analysis suggests that permeability and porosity variation within these facies is due to textural and diagenetic differences. Outcrop based permeability correlation separated the studied deposits into reservoir (excellent or good) and non-reservoir (baffles or barriers) elements. The relatively thick (5–10 m) and laterally continuous (hundreds of meters) siliciclastic deposits form excellent and good reservoir compared to usually thinner (1–2 m) mixed siliciclastic-carbonate and carbonate beds, which may act as baffles and barriers. This reservoir-seal configuration highlights the potential of stratigraphic trap formation in analogous settings in the subsurface, where non-marine siliciclastic deposits show lateral transition to marine carbonates.
... However, to date, particle shape variation was mainly investigated in glacial, fluvial, beach, aeolian and coastal depositional settings, whereas deep-water sediments have received little attention (Marchand et al., 2015;Bell et al., 2018). Pyles et al. (2013) documented spatial fractionation of grains based on their shape and density, using soda-lime and zirconia-silicate glass particles in experimental gravity flows. Except for siliciclastic particles, several recent studies also documented hydrodynamic fractionation of organic material within sediment gravity flow deposits (McArthur et al., 2016a(McArthur et al., , 2016b(McArthur et al., , 2017Schnyder et al., 2017). ...
... To investigate whether the experimental flows generated could be dynamically compared with natural flows, scale analysis was applied, using two reduced scale methodologies previously described for similar flow experiments (Pyles et al., 2013;Baas et al., 2014). Using both of the proposed methods, the upscaling of experimental results to reality based on observed parameters (for example, for deposit geometries and dimensions, Fig. 3) was in good approximation compared with values reported in the literature for flow characteristics and deposits of natural turbidity flows. ...
... The prevalence of these more irregularlyshaped, platy particles within the distal and marginal areas of studied experimental deposits, indicates possible effects of studied experimental flows, which probably segregated the particles incorporated within them based on their shape: irregularly shaped particles were probably much easier to keep in suspension which would explain their observed increasing trend as a result of along-flow hydraulic fractionation in a similar manner to previous studies (Pyles et al., 2013). However, coal particles from bypass samples are generally less-rounded (Figs 9, 10 and 11), implying a slight shape modification of the initial coal particles along the flow, also implied by the weak increasing downflow trends in roundness values within the experimental basin. ...
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 Accepted Article This article is protected by copyright. All rights reserved 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.
... In proximal energetic fan sectors muds may either be very thin or not expressed at all [11,57]. Organic carbon carried by sediment gravity flows is also often sorted with mud in the mudstones because of their platy particle shape, which facilitates slower settling than denser, relatively rounded, coarser clastic grains (such as quartz and feldspar) with which they are transported [72,73]. Conventional models argued that for preservation of OM bottom water anoxia is prerequisite [71]. ...
... However, a limited number of studies have documented the impact of rapid deposition on enhanced preservation of OM in mudstones and transitional flow processes in fine-grained deep-water successions. [72,73]. Conventional models argued that for preservation of OM bottom water anoxia is prerequisite [71]. ...
Organic matter burial in the deep-sea fan sediments is an important component of the
long-term carbon cycle. Although there is increasing recognition of the importance of organic matter in deep-sea sediments, a major focus has been on mudstones, commonly interpreted as the background sediments, deposited by pelagic or hemipelagic vertical suspension fallout in low-energy fan environments. Emerging evidence suggests that relatively coarse-grained sediment gravity flow deposits (e.g., turbidites and hybrid event beds) can also store a significant quantity of organic carbon, implying that a wide range of depositional processes can result in the concentration and enrichment
of organic matter in submarine fans. However, the role of these processes on carbon burial is still not fully understood. This review aims to discuss the impact of three widely documented deep-sea depositional mechanisms/processes, namely vertical suspension settling, grain-by-grain (incremental aggradation), and the en-masse deposition on distribution, burial, and preservation of organic matter in deep-marine deposits. Organic matter accumulated from slowly settling suspension in mud caps (Te or H5 divisions of turbidites and hybrid beds, respectively) is prone to higher oxidation
compared to the carbon buried in sandy components of turbidity currents (Ta-Tc units) and hybrid beds (H2/H3 divisions). The burial of organic matter in sandy parts of the deposits has important implications for understanding the fundamental physical processes that control carbon accumulation and preservation in deep-marine rock record.
