Article

Intrabasinal and Extrabasinal turbidites: origin and distinctive characteristics

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The discovery of turbidites represents perhaps themajor genuine advance of sedimentology during the twentieth century. Turbidites are the deposits of turbidity currents and were originally related to the gravitational instability and re-sedimentation of previously accumulated shallow water sediments into deep waters. As these flows originate and entirely evolve within a marine or lacustrine basin, their associated deposits are here termed intrabasinal turbidites. Controversially, increasing evidences support that turbidity currents can also be originated by the direct discharge of sediment–water mixtures by rivers in flood (hyperpycnal flows). Since these flows are originated in the continent, their associated deposits are here termed extrabasinal turbidites. Deposits related to these two different turbidity currents are often confused in the literature although they display diagnostic features that allow a clear differentiation between them. Intrabasinal turbidites are mostly related to surge-like (unsteady) flows that initiate from a cohesive debris flow that accelerates along the slope and evolves into a granular and finally a turbulent flow. Its flow behavior results on the accumulation of normally graded beds and bedsets that lacks terrestrial phytodetritus and lofting rhythmites. Extrabasinal turbidites, on the contrary, are deposits related to fully turbulent flows having interstitial freshwater and sustained by a relatively dense and long-lived river discharge. According to the grain size of suspended materials, hyperpycnal flows can be muddy or sandy. Sandy hyperpycnal flows (with or without associated bedload) often accumulate sandy to gravelly composite beds in prodelta to inner basin areas. Their typical deposits show sharp to gradual internal facies changes and recurrence, with abundant plant remains. In marine waters, the density reversal induced by freshwater results in the accumulation of lofting rhythmites at flow margin areas. Muddy hyperpycnal flows are loaded by a turbulent suspension dominantly composed of a mixture of silt and clay-sized particles (b62.5 μm) of varying compositions. Since the suspended sediment concentration does not substantially decrease in waning flows, muddy hyperpycnal flows will be not affected by lofting, and the flow will remain attached to the sea bottom until its final accumulation. Typical deposits compose cm to dm-thick graded shale beds disposed over an erosive base with displaced marine microfossils and dispersed plant remains.
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... They are called earthquake-related turbidites and flood-related turbidites (i.e. hyperpycnites), also intrabasinal and extrabasinal turbidites (Zavala & Arcuri, 2016). Several studies have highlighted that, in modern small lake basins, earthquake-related turbidites are typically thicker than hyperpycnites (Gorsline et al., 2000;Wirth et al., 2011). ...
... Plant fragments (Figs 7B and 10A to C) and reddish mud clasts (Figs 10A, 10B, 10F, 11B and 12A) were probably transported from outside the basin into deep-lake settings, indicating an extrabasinal origin (Mulder et al., 2003;Zavala et al., 2011;Zavala et al., 2012;Zavala & Arcuri, 2016). Moreover, cross-laminations in B2s (Figs 10D, 10E and 12B) and the ripples in S3 (Fig. 11D to F) reflect relatively long-lived sedimentary behaviour (Baas, 1999;Zavala et al., 2011), which is the nature of hyperpycnal flows (Mulder et al., 2003). ...
... Depositional architecture Submarine hyperpycnal-flow channels or canyons serve as the primary conduits in delivering sediment, which has been directly observed and widely accepted by many researchers (Camacho et al., 2002;Mulder et al., 2003;Talling et al., 2013;Zavala & Arcuri, 2016). Welldeveloped hyperpycnal-flow channels also occur in many modern lakes, such as Lake Walensee (Switzerland; Lambert & Hsu, 1979), Lake Mead (USA; Twichell et al., 2005), Lake Kivu (East Africa; Zhang et al., 2014), Lake Geneva (France-Switzerland; Kremer et al., 2015b;Corella et al., 2016), and also have been recognized in ancient lakes, such as in the Cretaceous Rayoso Formation in the Neuquén Basin (Argentina; Zavala et al., 2006) and in the Cretaceous Songliao Lake (China; Pan et al., 2017). ...
Article
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Turbidites have been regarded as an important sedimentary infilling component in both oceans and lakes, but limited studies have been performed on the mechanisms governing the initiation and development of lacustrine turbidite systems. The present study offers unique insight into the controls and potential extent of ancient lacustrine turbidite systems by an investigation of the Triassic Ordos Lake, where a large turbidite system had been traced across >25 653 km2. This article shows by comparison that the Triassic Ordos Lake turbidite system is larger than all known modern and ancient lacustrine counterparts. The exceptionally large intracontinental sag basin provided a relatively unconfined environment for the development of the turbidite system, explaining its vast extent. Extraordinary flood events formed during the Carnian Pluvial Episode facilitated continuous sediment supply into the turbidite system, supporting its accumulation. Lacustrine flood-related turbidity currents travelled as sediment-laden turbulent flows, showing an increase in the proportion of suspended-load deposits and a decrease in the proportion of bed-load deposits downstream from the river mouth. Five architectural elements have been revealed, reflecting a distinctive assemblage of erosional bedforms and depositional bedforms in channel-lobe systems, and their recognition criteria were established. This study changes the traditional understanding of lacustrine turbidite systems, generally interpreted as having smaller sizes, and demonstrates likewise in the lacustrine realm, that extreme flood events can generate a world-class deep-water turbidite system, which can even be comparable with its submarine counterparts. This study also confirms that the combination of low-gradient slopes and a long-lived, mixed-load, prograding fluvial feeder system can produce exceptionally large-scale deep-lake flood-related turbidites. Furthermore, it has implications for the prediction of facies and reservoir quality in ancient lacustrine turbidite systems.
... Hyperpycnal flows are extrabasinal sustained turbidity currents generated by river flooding (Wright et al., 1986;Mulder et al., 2003;Zavala and Arcuri, 2016), and their depositshyperpycniteshave been documented in both modern environments and the sedimentary rock record (Best et al., 2005;Soyinka and Slatt, 2008;Xian et al., 2018). However, the identification and distribution of ancient hyperpycnites is currently the subject of much debate (e.g. ...
... However, research over the past twenty years has shown that clay-laden flows may show a transitional behavior between fully turbulent and quasi-laminar plug flows (Baas and Best, 2002;Baas et al., 2011Baas et al., , 2016. These transitional flows may generate a range of unique bedforms (Baas et al., 2019;Peakall et al., 2020;Baas et al., 2020) that may be expected within the deposits of delta-fed hyperpycnal flows with mixed sand-clay loads (Zavala and Arcuri, 2016). However, the effects of such flows are not currently well-incorporated into facies models of hyperpycnal flows and we still possess an incomplete knowledge of the role, and properties, of transitional flows in hyperpycnite deposition. ...
... The rounded, imbricated mud clasts reflect substrate erosion at the bottom of overpassing flows, with these clasts either being sheared within the flow or transported as a basal traction load. This substrate erosion indicates the velocities of the overpassing flows exceeded the erosional threshold of the underlying lacustrine muds (Zavala and Arcuri, 2016), which may have occurred under initially turbulent or transitional flows that could generate erosion, traction and clast abrasion. Such substrate erosion likely increased the clay content in any initially turbulent flows and aided the transformation from turbulent to transitional flows (Baker and Baas, 2020). ...
Article
Hyperpycnal flows are river-derived extrabasinal turbidity currents transporting both sand and clay to lacustrine, coastal, shelf and deepwater sedimentary environments. Experimental research in the past twenty years has shown that the presence of clay in sediment-laden flows promotes a transitional behavior between fully turbulent flow and a quasi-laminar plug flow regime. However, to date, most work concerning the fluid dynamic interpretation of lacustrine hyperpycnal flows has been founded on concepts based on fully turbulent flows, and relatively little is known about the influence of clay on the rheological and turbulence characteristics of these flows. With the help of 3D seismic volume and wire-line logging data, the present study undertakes a description and interpretation of subsurface mixed sandstone–mudstone bedforms observed in cores from the Upper Cretaceous Heidimiao Sandstone, Nenjiang Formation, Songliao Basin, NE China. Six lithofacies and five lithofacies associations are recognized from the cores and interpreted as formed under both turbulent and transitional flows. Typical bedforms of transitional flows include large current ripples and low-amplitude bedwaves. The delta-fed shallow lacustrine hyperpycnal flow deposits are characterized by proximal sinuous channels (extending for c. 20 km) and lobe deposits (extending for >20 km), showing a fan-like geometry associated with distributary channel extension in the down-dip direction. Basal erosion in the proximal channels is produced by the initial turbulent and turbulence-enhanced transitional flows, with channel infill dominated by upper transitional plug flows or quasi-laminar plug flows. The lobe deposits possess a fan-like geometry with large aspect ratio, and were formed from turbulence-enhanced and lower transitional plug flows. The downdip transformation of sediment-laden flows in the lacustrine basin varies from an initial turbulent flow, via quasi laminar plug flows to upper and lower transitional plug flows, to turbulence enhanced transitional flows. These transitional flows are interpreted to have experienced gradual dilution and deceleration and eventually transformed to turbulent flows in their distal regions. A new model for delta-fed shallow lacustrine hyperpycnal flow deposits is presented incorporating decelerated transitional flows and flow transformations. This new model can aid understanding of the depositional processes of lacustrine transitional flows and the facies distribution of hyperpynal flows in both modern and ancient sediments.
... The paleorelief in the deeplacustrine environment controlled the distribution of gravity-flow sedimentary deposits that exhibit extreme variation of thickness and reservoir heterogeneity (Dodd et al., 2019;Guo et al., 2021). Hyperpycnal currents related to river floods occur more readily in lake basins than in marine basins (Mulder et al., 2003;Zavala and Arcuri, 2016), and carry clastic particles and organic matter together into the deep lake to form reservoirs and source rocks. Gravity-flow of sediment following slope collapse and related to river flooding can also carry sandy sediments into the deep lake, and may form reservoirs (Zavala and Arcuri, 2016;Yang et al., 2017b;Fan et al., 2018). ...
... Hyperpycnal currents related to river floods occur more readily in lake basins than in marine basins (Mulder et al., 2003;Zavala and Arcuri, 2016), and carry clastic particles and organic matter together into the deep lake to form reservoirs and source rocks. Gravity-flow of sediment following slope collapse and related to river flooding can also carry sandy sediments into the deep lake, and may form reservoirs (Zavala and Arcuri, 2016;Yang et al., 2017b;Fan et al., 2018). ...
... LA1, which shows a typical fining-upward interval characterized by normally graded bedded sandstones with granules and aligned clasts and erosional surfaces, was identified in the cores from wells X125 and N5 ( Fig. 10A and B) penetrating the channel fills shown in yellow color in Fig. 12A. LA1 has been interpreted as bedload at the base of the sustained sand-rich concentrated density flows (Mulder and Alexander, 2001;Zavala and Arcuri, 2016;Li et al., 2017) filling the channel axes ( Fig. 10A and B). ...
Article
The Songliao Basin is a large Cretaceous nonmarine petroliferous postrift downwarped basin in northeastern China. Deep lake channel-levee-lobe and slope fan deposits are identified within six depositional sequences that span from the Turonian Qingshankou Formation to the second member of the Campanian Nenjiang Formation. Research on the sediment gravity-flow systems in the Songliao Basin has broad application for understanding the sedimentary processes and pattern of sediment gravity-flow systems, and predicting the presence of good sandstone reservoirs within postrift downwarped lacustrine basins. Research results show that the channel-levee-lobe deposits are present within sequences in the first member of the Qinshankou Formation and the first member of the Nenjiang Formation. The straight channel levees and slope fans were on high-gradient slopes, whereas the sinuous channel levees were on low-gradient slopes. The straight-to-sinuous channel levees, fed by northeastern deltaic subaqueous distributary channels, extend for 15–70 km, predominantly within transgressive-to early highstand system tracts, which terminated in bifurcated or small lobes. The channel-levee-lobe and slope fan deposits sourced from western deltas were deposited basinward of the syndepositional flexural slope-break zones controlled by deep-seated faults. The falling trajectories of the paleoshorelines during the highstand and lowstand systems tracts and large sediment fluxes during the transgressive systems tracts resulted in the development of the slope fans and channel-levee-lobes. Lakebed paleorelief influenced the channel forms. Sand bodies within the channel-levee-lobes and slope fans, encased within organic-rich source rocks, represent new significant targets for hydrocarbon exploration.
... Hyperpycnal flows are river-derived, quasi-steady underflows that are capable of transfer huge volumes of sediments from the land to the shelf and potentially further to deep-basins (Bates, 1953;Wright et al., 1988;Mulder and Syvitski, 1995;Mutti et al., 2009), which play an import role in sediment transport from source to sink and deep-water sediment partitioning (Mulder et al., 2003;Sømme et al., 2009). Deposits from hyperpycnal flows host relative complete and high-precision information of climate changes compared to on-shore records and constitute important targets in deep-water petroleum exploration as well (Warrick and Milliman, 2003;Zhang et al., 2014;Xian et al., 2018a;Liu et al., 2020;Chen et al., 2021), which have drawn increasing attention in recent years and the origination, transport mechanism and depositional process of which are still topics on debate (Lamb et al. 2010;Talling, 2014;Zavala and Arcuri, 2016;Xian et al., 2018a;Shanmugam, 2018;Zavala and Pan, 2018;Zavala, 2019;van Loon et al., 2019). ...
... Modern river investigations suggest that critical concentration needed to produce hyperpycnal plumes at a river mouth into a freshwater lake is much lower (≪ 1 kg m − 3 ) than in marine water (>36 kg m − 3 ) (Mulder and Syvitski, 1995;Mulder et al., 2003), which suggest that hyperpycnites may be probably extremely common in lacustrine records. However, our understandings of hyperpycnal flows or "extrabasinal turbidites" are still incomplete and less enough compared to the well-studied surge-like turbidity currents and "intrabasinal turbidites" (Mutti et al., 2009;Zavala and Arcuri, 2016;Shanmugam, 2018). Additionally, limited experience on hyperpycnite deposition is mainly built on information obtained from long-transport hyperpycnal flows in structurally stable areas, such as marine basins (Mulder et al., 2003;Petter and Steel, 2006;Bourget et al., 2010;Warrick et al., 2013;Zavala and Arcuri, 2016;Steel et al., 2016Steel et al., , 2018 or large depressed lake basins (Feng et al., 2010;Pan et al., 2017;Yang et al., 2017a, b;Xian et al., 2018a;Chen et al., 2021), whereas the characteristics of hyperpycnal system in tectonically active rift-basins are still less understood, from which the depositional process and dispersal pattern may be significantly different and the controlling mechanisms may be highly varied, in terms to frequent and episodic tectonic movements and geomorphological differences. ...
... However, our understandings of hyperpycnal flows or "extrabasinal turbidites" are still incomplete and less enough compared to the well-studied surge-like turbidity currents and "intrabasinal turbidites" (Mutti et al., 2009;Zavala and Arcuri, 2016;Shanmugam, 2018). Additionally, limited experience on hyperpycnite deposition is mainly built on information obtained from long-transport hyperpycnal flows in structurally stable areas, such as marine basins (Mulder et al., 2003;Petter and Steel, 2006;Bourget et al., 2010;Warrick et al., 2013;Zavala and Arcuri, 2016;Steel et al., 2016Steel et al., , 2018 or large depressed lake basins (Feng et al., 2010;Pan et al., 2017;Yang et al., 2017a, b;Xian et al., 2018a;Chen et al., 2021), whereas the characteristics of hyperpycnal system in tectonically active rift-basins are still less understood, from which the depositional process and dispersal pattern may be significantly different and the controlling mechanisms may be highly varied, in terms to frequent and episodic tectonic movements and geomorphological differences. ...
Article
There has been an increased attention on hyperpycnal flows due to its importance in delivering large volumes of sediments into deep-water. The process and products of hyperpycnal flow in tectonically-active margins are still poorly understood, and potentially constitute one of the most important deep-water mechanisms in rift basins. This study integrates core data, well-logging and 3D seismic data to investigate the hyperpycnal flow process and dispersal pattern on the Eocene Dongying rift margin. 17 facies, including 5 conglomerate facies, 9 sand facies and 3 mud facies are identified, interpreted as the product of debris flows, traction currents, turbidity currents, transitional flows and lofting plumes, and suggesting the complex blend in flood-triggered hyperpycnal flow on rift margin. Two different hyperpycnal flow types are identified and a related process model is proposed based on facies sequence, distribution, transport mechanism and flood discharge analysis, including seasonal-flood triggered hyperpycnal flow (SHF) and outburst-flood triggered hyperpycnal flow (OHF). The evolution of the hyperpycnal system suggests two dispersal styles, including proximal sublacustrine fan dominated by OHF and distal sublacustrine fan dominated by SHF, respectively. Climate and tectonic movements are suggested to be the main factors controlling hyperpycnal flow generation and deposition on rift margins. The relatively arid climate enhanced seasonal-flood activity and associated sustained and stable SHF, which further prompt distal sublacustrine fan development during a weak rifting period. On the other hand, the generation of outburst-floods can be attributed to the enhanced fault activity, which corresponds to the periodical tectonic movements in the basin. As a result, proximal sublacustrine fans tend to develop in near-shore topographic lows down-dip of syn-depositional faults due to increased tectonic activities, accommodation and enhanced OHF. A deep-water depositional model is proposed for hyperpycnal systems on rift margins by emphasizing the variety in sedimentary process and dispersal patterns controlled by climate and tectonics forces, which may provide new insights into hyperpycnal flow theories and deep-water exploration in world rift basins.
... The investigation of the sedimentology of fine-grained deposits, similar to the Chengjiang Biota, has experienced a paradigm shift during the last couple of decades [29][30][31][32][33][34] . Many mudstonedominated successions originally regarded as having formed owing to slow suspension fallout are now reinterpreted as having been produced by a complex array of depositional mechanisms, such as hyperpycnal flows, fluid muds, ocean floods, turbidity currents, and bottom currents, among other processes [35][36][37][38][39][40][41] . This recent way of investigating and interpreting fine-grained systems has rarely been applied systematically to the study of Burgess Shale-type deposits preserving soft anatomies in the Cambrian. ...
... Vertical alternation of sedimentary structures suggests common fluctuations inflow velocity. Accordingly, these deposits are interpreted as the product of flood-derived, sustained hyperpycnal flows that occurred simultaneously with storms 28,40,45,47 . Alternatively, some of the beds with evidence of waning flows may represent turbidity flows associated with mouth bar collapse. ...
... However, the local alternation of parallel-laminated and inversely and normally graded divisions with diffuse contacts suggests flow fluctuation. Accordingly, these intervals may have been produced by floodderived, sustained hyperpycnal flows 40,47 . The local presence of wavy parallel lamination indicates oscillatory flows associated with storms, which may have reworked and enhanced the hyperpycnal flows 48 . ...
Article
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The Chengjiang Biota is the earliest Phanerozoic soft-bodied fossil assemblage offering the most complete snapshot of Earth's initial diversification, the Cambrian Explosion. Although palaeobiologic aspects of this biota are well understood, the precise sedimentary environment inhabited by this biota remains debated. Herein, we examine a non-weathered core from the Yu'anshan Formation including the interval preserving the Chengjiang Biota. Our data indicate that the succession was deposited as part of a delta influenced by storm floods (i.e., produced by upstream river floods resulting from ocean storms). Most Chengjiang animals lived in an oxygen and nutrient-rich delta front environment in which unstable salinity and high sedimentation rates were the main stressors. This unexpected finding allows for sophisticated ecological comparisons with other Burgess Shale-type deposits and emphasizes that the long-held view of Burgess Shale-type faunas as snapshots of stable distal shelf and slope communities needs to be revised based on recent sedimentologic advances.
... (Zavala et al., 2006, Xian et al., 2018bZavala et al., 2018). Massive sandstones consist of composite rhythms with inverse-normally grain size in facies Sc ( Fig. 7D) indicating that the flow underwent a waxing-waning process, which are the products of hyperpycnal flows related to flood discharges fluctuations (Mulder et al., 2003;Zavala et al., 2016;Xian et al., 2018b;Chen et al., 2021;Liu et al., 2022). In addition, under the humid condition (Fig. 4B), floods might be more frequent in lacustrine basins during the HNR stage (Mulder et al., 2003;Zhang and Scholz, 2015;Chen et al., 2021;Guo et al., 2021). ...
... Three-banded turbidite systems are shown in the amplitude slice within PSS4 (Fig. 6E). The distal deposits of the intervening system are primarily composed of LA1, which indicates the channel element was filled with both bed-load and suspended-load sediments (Zavala et al., 2016;Xian et al., 2018b). The responses in the GR logs at the centre of banded turbidites are characterized by a low-amplitude bell-or box-shape (Fig. 11), usually indicative of channel deposits. ...
... The proportions of lithofacies associations based on the thickness in three regression stages (The location of the cored well is shown in Fig. 1C). J o u r n a l P r e -p r o o f Bed-load (Zavala et al., 2016;Xian et al., 2018b). Sandy debris flows (Sohn et al., 1999;Shanmugam 2012Shanmugam , 2016Dasgupta, 2003). ...
Article
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Sedimentary processes of marine turbidite systems under sea-level changes have been the focus of deep-water sedimentology. Compared with well-studied marine basins, the products of deep-water sediment gravity flows responding to lake-level changes in closed lacustrine basins are still poorly understood. In this study, we integrate cores of 10 exploratory wells, logs of 280 development wells, 3D seismic data and geochemical elements from the Eocene Dongying Depression, Bohai Bay Basin, East China to investigate sedimentary mechanisms and depositional architecture of lacustrine turbidite systems under lake-level changes. The studied strata are divided into three parasequence sets (PSS4~PSS2), corresponding to early highstand normal regression with ascending trajectories, late highstand normal regression with flat trajectories, and forced regression with descending trajectories, respectively. From early highstand normal regression to forced regression, the ratios of Fe/Mn and U/Th reveal that the humid climate shifted to the arid climate. More lithofacies clues indicate that turbidites in highstand normal regression were triggered by river floods, whereas counterparts in forced regression were related to sediment failures. There are different architectural features of turbidite systems in three regression stages. PSS4 developed a series of channel belts within which individual channel elements are aggraded vertically. PSS3 is composed of a channelized lobe formed by individual distributary channels migrating laterally. PSS2 is characterized by a suite of compensational stacking debrite tongues. Climate forcing is a crucial factor controlling depositional architecture of the turbidite systems. A relatively humid climate during highstand normal regression led to rising lake-level and frequent floods, which are conducive to the formation of hyperpycnal-fed channel-lobe systems. Nevertheless, during forced regression under an arid climate, the strong progradational clinothems were prone to failure and sediment remobilization, resulting in debrite tongue complexes. This study highlights depositional differences of lacustrine turbidites during regression stages under the control of climate. Meanwhile, it also provides a new predictive model for deep-water hydrocarbon exploration and production in lacustrine basins worldwide.
... Deposits accumulated by hyperpycnal flows are termed hyperpycnites, which can be sandy and muddy in composition (Mulder et al., 2003;Zavala & Pan, 2018). Hyperpycnites are characterized by well-developed inversely and normally graded facies, with or without internal erosional contacts, as well as a high content of terrestrial plant debris and therefore differ from other turbidites (Mulder et al., 2003;Zavala & Arcuri, 2016;Zavala, Arcuri, & Blanco Valiente, 2012). The complete sequence of a typical hyperpycnite consists of a basal coarsening-upward interval followed by an overlying fining-upward interval deposited during the waxing and waning period of the river discharge, respectively (Mulder et al., 2003;Mulder & Chapron, 2011;Zavala & Pan, 2018). ...
... Deep lacustrine facies were deposited in the centre of the basin, while shallow lake sediments were deposited in the southern part, and sub-lacustrine fan deposits were deposited in the northern part (Feng et al., 2006;Feng, Jia, et al., 2010;. Based on the analysis of high-resolution three-dimensional seismic data, Feng et al. (2006) and identified large-scale sub-lacustrine channels (Lamb & Mohrig, 2009;Mulder et al., 2001Mulder et al., , 2003Mulder & Chapron, 2011;Yang et al., 2017Yang et al., , 2018Zavala et al., 2012;Zavala & Arcuri, 2016). Different from hyperpycnal flows, the chaotically distributed floating mudstone clasts are the very distinct sedimentary features present in the deposits of muddy debris flows (Locat & Lee, 2005;Pierson, 2005;Qian & Das, 2019;Shanmugam, 2016). ...
... Hyperpycnal flows have been previously proposed as an important depositional mechanism for the First Member of the Nenjiang Formation (Feng et al., 2006;Mo et al., 2013;Pan et al., 2020). However, previous works F I G U R E 6 (a) Different muddy hyperpycnites produced by floods with varying magnitudes (Modified from Mulder et al., 2003); (b) Waxing and waning states of different muddy hyperpycnites (Modified from (Kneller & Branney, 1995;Mulder et al., 2003) (Zavala & Arcuri, 2016;Zavala & Pan, 2018;Zavala, 2020). Lofting occurs in marine (or saline) basins because of flow density reversal due to the buoyant effect of freshwater when a waning turbulent flow loses part of the sandy load (Zavala et al., 2011(Zavala et al., , 2012. ...
Article
The Songliao Basin in NE China is a large rift basin filled with Cretaceous terrestrial sediments. Lacustrine mudstones of the Nenjiang Formation form an important source rock in the Cretaceous Songliao Basin. These shales are commonly thought to have been deposited in deep, quiet, and anoxic environments. Samples obtained from the core of the SK‐2 scientific borehole provide critical insights to understand the hydrodynamic and hydroclimatic environments, which are, however, different from the traditional views regarding the deposition of these rocks. By following a mudstone description guide, five different mudstone lithofacies (LF) transported and deposited by muddy hyperpycnal flows and muddy debris flows were recognized. They are laminated fine mudstone (LF1), laminated medium mudstone (LF2), and laminated coarse mudstone (LF3) showing pairs of inverse grading (Ha) and normal grading (Hb) under the microscope, graded coarse mudstone (LF4) and massive coarse mudstone (LF5). We found that mudstones of the First Member of the Nenjiang Formation are dominated by siliciclastic detritus and argillaceous components and show frequent variations in grain size. Because large‐scale sub‐lacustrine channels travelling long distance (>80 km) were widely distributed in the Songliao palaeolake during the deposition of the Nenjiang Formation, fluctuations in mudstone grain size might have been caused by velocity fluctuations in flows. Sedimentary structures and textures preserved in mudstones of the First Member of the Nenjiang Formation indicate that the majority of these lithofacies were accumulated by muddy hyperpycnal flows and muddy debris flows. Therefore, a depositional model dominantly influenced by muddy hyperpycnal flows and debris flows is proposed. This work not only provides a new view for the depositional process of mudstones of the Songliao Basin, NE China, but also give insights to understand lacustrine palaeoenvironment and terrestrial palaeoclimate.
... Mudstones commonly compose dm-thick graded beds with abundant plant remains disposed over sharp or erosional boundaries (Fig. 2b). These characteristics suggest the common occurrence of muddy hyperpycnal flows probably punctuated by normal fallout processes from hypopycnal buoyant plumes (Zavala and Arcuri 2016). Hyperpycnal flows develop at river mouth when the fluvial discharge has higher bulk density respect to that of the water in the sea, due to the high suspended load in the incoming flow. ...
... Consequently, hyperpycnal flows are considered an efficient mechanism for the erosion and basinward transport of sediments and microfossils initially stored in littoral/shallow-marine environments (Zavala and Pan 2018). Therefore, the final products of these flows commonly show a mixture of intrabasinal (autochthonous) and extrabasinal (allochthonous) components, reflecting a complex sedimentological and taphonomic history (Lash 2016;Zavala and Arcuri 2016). ...
Article
Being the main oil-bearing basin of Argentina, the Neuquén Basin contains a well-documented stratigraphic record of continental and marine sedimentation during the Jurassic and Cretaceous in the western margin of Gondwana. Marine sedimentation started in the Early Jurassic with the deposition of the offshore to prodelta shales of the Los Molles Formation, the basal unit of the Cuyo Group. A palynological study of outcrop samples of the Los Molles Formation at two localities, Puente Picún Leufú, southern Neuquén Basin, and Cordillera del Viento, central basin area, is presented. The palynological evidence allows inferring two different palaeoceanographic contexts during the deposition of the Los Molles Fm. At Puente Picún Leufú and the lower part of the Cordillera del Viento localities, the record of acritarchs and prasinophytes suggests a stratified water column, suboxic-to-anoxic bottom conditions, and a reduced salinity within the photic zone, associated with a marginal marine environment under restricted oceanic circulation. These conditions would have last at least until the Early Bajocian. Conversely, at the middle and mainly the upper part of Cordillera del Viento locality, the predominance of dinocysts in the assemblages indicates a hydrographically unstable shelf (non-stratified water mass column) with well-oxygenated bottom waters developed under open-marine settings with non-restricted oceanic circulation. The abundance and diversity of dinocyst assemblages are comparable with those observed in the Late Callovian Lotena Formation. These evidences suggest an open oceanic circulation due to the establishment of different seaways in the Neuquén Basin, during the final accumulation of the Los Molles Formation (Early Callovian).
... Deep-water deposits in the lacustrine system have been of great interest for the identification, classification and prediction of gravity flows in recent years (Fugelli and Olsen, 2007;Jobe et al., 2017;Porten et al., 2016;Southern et al., 2015;Stevenson et al., 2014;Talling et al., 2007;Talling, 2014;Talling et al., 2015;Tinterri et al., 2016;Zavala and Arcuri, 2016). According to different grain sizes and sedimentary structures, the sublacustrine turbidite sediments were classified as flood turbidites (quasi-steady turbidites) resulting from flooding and slump turbidites (surge-like turbidites) resulting from sediment slumping Yang et al., 2019). ...
... The relatively coarse grain size, mudstone rip-up clasts, superposition of upward-coarsening and upward-fining sequences, and mudstone with vermiform sand bands match well with the hyperpycnal flow of deposits that were suggested to be flood-induced turbidites Zavala and Arcuri, 2016). The corresponding bed load sediments (pebble-and clay chip-supported conglomerates, Fig. 6q-r) and suspended load sediments (climbing ripples and small-scale cross-bedding, Fig. 6s-u) are also developed, as suggested by Zavala et al. (2011). ...
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The influence exerted by the linkage and growth of fault segments on the sedimentation pattern in a lacustrine rift subbasin, the northern Bonan Sag in the Jiyang Depression in the Bohai Bay Basin, is studied by integrating drilling cores, wireline logs and 3D seismic data. The NW-trending Guxi Fault formed through the linkage of three fault segments, which display a roughly en echelon arrangement in map view and are probably related to early-stage regional transtensional and slip-strike stress. Between the vertical displacement troughs of normal faults, two narrow relay ramps, attributed to the coherent fault linkage-and-growth model, formed through the linkage of the three fault segments. A relatively wide relay ramp, attributed to the isolated fault linkage-and-growth model, developed due to the linkage of the NW-trending Guxi Fault and E-W-oriented segmented Chengnan Fault. The sedimentation pattern was strongly controlled by the geometry and evolution of the relay ramps. The sediment routing system was dominated by the relay zone, and fan-delta and sublacustrine fan depositional systems developed in the early stage of relay ramp formation. Lateral breaching of the relay ramps through extensive faulting and rifting probably caused an increase in the vertical throw and resulted in deposition of a coarse-grained nearshore subaqueous fan in front of the normal faults. The relay zone that formed from the linkage of independent faults (the Chengnan and Guxi faults) is associated with a broad drainage area and fan-delta and sublacustrine fan deposits, which contain the most effective hydrocarbon reservoirs in this deeply buried setting.
... Laminated beds next to diamictites are, by association, commonly interpreted as glaciogenic rhythmites or varves, without closer inspection or discussion of different interpretations. The laminated layers described in the present paper do not display an appearance that is typical of glaciogenic varves but they are more closely similar to rhythmites deposited by turbidities (e.g., Schwab, 1981;Lowe, 1988;Domack, 1990;Eyles & Januszczak 2007;Isbell et al., 2008;Zavala & Arcuri, 2016), as seen from their internal structure (thickness of "winter/summer" layers, division of layers into thin sublam-inae, presence of boudins, climbing ripples, load casts and clastic dike) and the appearance of the lonestones. These features of the rhythmites in the Gowganda Formation are typical of rapidly deposited sediments, but commonly not of yearly varves. ...
... This conforms well with the evidence of tectonics and sedimentation from many Precambrian diamictites worldwide, which also could help explain stepwise oxygenation of the Earth´s atmosphere resulting from tectonics (Eyles, 1993;Eguchi et al., 2020). The origin of the basal "tillite" is interpreted to be "the missing fan facies" and to have been deposited by cohesive debris flows, possibly as hyperpycnal flows which may be deposited as a full spectrum of gravity flows including cohesive debris flows and rhythmites (Zavala & Arcuri, 2016;Shanmugam, 2019;Zavala, 2019Zavala, , 2020. ...
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During more than a century since its original identification, the Gowganda Formation in Ontario (Canada) has gradually been reinterpreted from representing mainly subglacial tillites to secondary gravity flow and glaciomarine deposits. The main pieces of geological evidence advanced in favour of glaciation in recent articles are outsized clasts that have been interpreted as dropstones and patches of diamictites in a single small-sized area at Cobalt which is still interpreted as displaying subglacial basal tillites. The present research considers field evidence in the Gowganda Formation in the light of more recent work on gravity flows linked to tectonics. Detailed studies have demonstrated that the clasts which are interpreted to be dropstones rarely penetrate laminae and are commonly draped by sediments the appearance of which is similar to lonestones in gravity flows. The “subglacial area” at Cobalt displays evidence of tectonics and gravity flows, which can be traced from the underlying bedrock, and then further in the overlying sequence of diamictites and rhythmites. The sum of geological features displays appearances at odds with a primary glaciogenic origin, and there is no unequivocal evidence present of glaciation. The data indicate deposition by non-glaciogenic gravity flows, including cohesive debris flows for the more compact units, probably triggered by tectonic displacements.
... The emphasis on turbidity flow deposits in recent years is because of their importance in the investigation of natural hazards, oil and gas exploration, and forecasting climate change (Embley, 1976;Hampton et al., 1996;Heller and Dickinson, 1985;Mutti et al., 2003;Shanmugam et al., 1994b;Weimer and Link, 1991). Turbidity currents, and their associated deposits, represent a vital step in sedimentological studies in both marine and lacustrine rift basins (Zavala and Arcuri, 2016). The fault break zones in lacustrine rift basins are related to continental shelf-slope systems in marine settings (Covault et al., 2009;Feng et al., 2016a;Mutti et al., 2003;Xiugang et al., 2014). ...
... The deltaic channels of this study (chapter 4 - Omosanya and Harishidayat, 2019) in the Eocene interval of the Great South Basinoffshore New Zealand, the Eocene deltaic channels in the Outer Moray Firthoffshore UK of Zimmer et al. (2019), and the Miocene-Pliocene deltaic channels in the Northwest shelf Australia of Ainsworth et al. (2019) are characterized by hummocky clinoforms with sigmoid or oblique reflection configuration (Figure 8. 2) The lacustrine channels in the Eocene interval of the Bohai Bay rift Basin -Onshore China (Lutome et al., 2020); 3) The fluvial channels in the Triassic interval of the Barents Seaoffshore Norway ; 4) The deltaic channels in the Eocene interval of the Great South Basinoffshore New Zealand (Omosanya and Harishidayat, 2019); 5) The shelf-edge to upper slope channels in the Cretaceous interval of the Barents Seaoffshore Norway ; 6) The shelf-edge canyons in the Cretaceous interval of the Barents Seaoffshore Norway ; 7) The deep marine channels in the Pliocene interval offshore Israel . Please note that circled numbers represent corresponding chapters in this thesis and the depositional environment cartoon is modified from Zavala and Arcuri (2016). ...
Thesis
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Canyons, channels, and gullies are incised features on the surface of the earth that act as subaqueous conduits for transferring sediment from source areas to basins. For several decades, these subaqueous sediment conduits have played an important role as storage for petroleum resources. An understanding of the architecture, morphometry, and development of these subaqueous sediment conduits in a general depositional environment will help maximize their potential. This study utilized 3D seismic reflection data obtained from various ancient subaqueous sediment conduits from fluvial, lacustrine, deltaic, and deep marine depositional environments from the Norwegian Barents Sea, offshore Israel, onshore China, and offshore New Zealand. The study aims to: 1) investigate their seismic stratigraphic architectures; 2) investigate their morphometric elements; 3) evaluate their sedimentary processes and paleoenvironments; and 4) compare their similarities and differences as well as global comparison with previous works. The results showed that isolated bright amplitudes with incised surfaces were characteristic of these subaqueous sediment conduits, while most of the conduits had morphometric elements, such as thalwegs, walls (including terraces), overspill points or levees, and flanks. These architectural and morphometric elements showed that gravity flow is dominant in subaqueous sediment conduits in the lacustrine and marine environments, and traction currents were observed in the subaqueous sediment conduits in the fluvial environments, as well as river-dominated deltas (minor marine influences). Furthermore, the subaqueous sediment conduits were similar with respect to the existence of incised surfaces and morphometric elements; however, their sedimentary processes, tectonics, climates (including latitudinal controls), and paleoenvironments were different. This research demonstrated that a comprehensive study of all depositional environments and the utilization of cutting-edge techniques for advanced seismic interpretations (quantitative seismic geomorphology, in particular) are necessary to appropriately interpret the sedimentary processes and paleoenvironments that lead to improved petroleum resources utilization.
... A hyperpycnal flow is a terrestrial sediment plume that plunges to form a sediment gravity flow where it enters a water body with a lower density (Bates, 1953;Lamb & Mohrig, 2009). The hyperpycnal flow is capable of transporting considerable volumes of sediment from the shoreline to the shelf and potentially farther to the deep ocean (Mulder et al., 2003;Mutti et al., 2003;Zavala & Arcuri, 2016;Steel et al., 2018). Previous works have led to an improved understanding of hyperpycnite sequences in ancient fluvial-deltaic systems (Mutti et al., 2000(Mutti et al., , 2003 and the deep sea environment (Mulder et al., 2001). ...
... Studies of modern and ancient hyperpycnites both suggest that the abundant terrestrial plant debris in the event beds is a diagnostic criterion of hyperpycnite (Plink-Bjorklund & Steel, 2004;Zavala et al., 2006Zavala et al., , 2011Zavala et al., , 2012Myrow et al., 2008;Zavala & Arcuri, 2016;Steel et al., 2018). In the present study, identical terrestrial plant fragments were found in both basal clean sand (H1) and muddy sand (H3a) divisions (Figs 3, 4, and 7), which suggest that flows responsible for the deposition of HEBs in the cored location probably originate from river flood-related hyperpycnal flows. ...
Article
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Hyperpycnal flows are important agents for transporting detrital sediments from rivers to oceans. Previous studies often assumed that the deposits of flood-controlled delta fronts would be dominated by graded sand with common hummocky cross stratification. This study documents, for the first time, hybrid event beds (HEBs) and plumite deposits inside the succession of a modern delta front. This delta in the Taiwan Strait is fed by the Choshui River, which is considered a highly efficient sediment transport system with individual floods with extremely high suspended sediment concentrations. The deltaic event beds recorded in the core were interpreted as hyperpycnal flow-generated HEBs and turbidites triggered by hypopycnal flows. AMS 14C dating, grain size analysis and measurements of stable isotopic composition of organic matter were conducted to delineate the depositional process of the recognized beds. The internal subdivisions of the HEBs were differentiated mainly based on sedimentary textures, including cohesive mud content, sand content and sorting. The disorganized portion (H3) appears internally chaotic and contains large rafted substrate clasts but also displays an upward increase in dispersed cohesive mud from 35% (H3a) to 50% (H3b). In contrast, massive H1 divisions are characterized by much lower cohesive mud of ca. 8%. The vertical arrangement between depositional facies allows the discrimination of three HEBs types. The stable carbon isotopic composition of the organic matter reveals that the cohesive mud in each division of the HEBs was sourced from marine substrate, rather than supplied by the original hyperpycnal flows. Therefore, the HEBs are generated by energetic hyperpycnal flows, which can delaminate the muddy sea-floor and incorporate large quantities of substrate fragments. The bulking of erosional hyperpycnal turbulent flow forces flow transformation and generates a more cohesive flow with a turbulent, dense head and trailing bipartite debris flow. The occurrence of HEBs in modern shallow delta front settings is also an important novelty, implying a high density of hyperpycnal flows at the mouth of sediment-laden rivers as well as the crucial impact of substrate entrainment on the development of HEBs.
... Subaqueous sediment gravity flows (SSGF) represent one of the most important sediment transport mechanisms on a global scale (e.g., Mulder and Alexander, 2001;Talling et al., 2007Talling et al., , 2015Meiburg and Kneller, 2010;Postma et al., 2021) and can result in extensive, thick bodies of coarse-grained clastic and associated fine-grained sediments on submarine slopes, on abyssal plains, and in deep lakes (e.g., Stow and Mayall, 2000;Talling et al., 2013;Yang et al., 2019;Dodd et al., 2019;McArthur et al., 2020). Considerable advances have been made in research related to subaqueous sediment gravity flows deposits (SSGFD), such as the classification of flow types (e.g., Postma, 1986;Mutti, 1992;Mulder and Alexander, 2001;Gani, 2004;Haughton et al., 2009;Talling et al., 2012;, transport mechanisms of SSGFs (Kuenen and Migliorini, 1950;Hampton, 1973, 1976;Lowe, 1982;Hage et al., 2018), the genesis of SSGFDs (Mutti et al., 2003(Mutti et al., , 2009Piper and Normark, 2009;Talling et al., 2013;Zavala and Arcuri, 2016;Yang et al., 2020), and the depositional elements and distribution patterns of SSGFD (Mutti andNormark, 1987, 1991;Reading and Richards, 1994;Shanmugam, 2000;Stow and Mayall, 2000;. Investigating the evolution of SSGF processes, and the distribution of the deposits from a sedimentary dynamics perspective is a key aspect of recent studies (e.g., Waltham, 2004;Haughton et al., 2009;Pierce et al., 2018). ...
... These were subdivided into twelve sub-facies defined on the basis of composition, sedimentary structures, and grading patterns (Table 1, Fig. 4). The terminologies used to describe and interpret the lithofacies mainly follow those of Bouma (1962), Lowe (1982), Pickering et al. (1986), Ghibaudo (1992), Haughton et al. (2009), Talling et al. (2012, Cartigny et al. (2013); Zavala and Arcuri (2016). ...
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Understanding how subaqueous sediment gravity flows (SSGF) evolve in time and space, and how their deposits vary spatially, is a key research focus for gravity flow sedimentology. This study investigates depositional facies, depositional elements, and sediment transport processes of supercritical flows and hybrid event beds (HEBs) of the Lingshandao Formation in Lingshan Island, Eastern China. Three kinds of depositional elements were recognized: mass transport deposits (MTDs), channel-lobe transition zone (CLTZs), and lobe complexes. MTDs can be sub-divided into proximal and distal deposits. CLTZs are characterized by facies changes from massive coarse-grained pebbly sandstone to backset bedding sandstone in a down-slope direction, which are the deposits of supercritical turbidity currents. HEBs are common in both proximal and distal lobe settings. Tripartite structure in HEBs, which may be caused by up-slope substrate erosion, implies a relatively proximal origin compared with bipartite HEBs, perhaps caused by fluid fractionation in the research area. The succession is formed by a prograding lobe unit, followed by MTDs which are themselves overlain by deposits from a CLTZ. This vertical stacking pattern implies the potential longitudinal facies tract from CLTZ; to lobe complex deposits, is accompanied by emplacement of MTDs at the slope break. The flow types accompanied by sediment transport processes imply that erosion by supercritical turbidity currents associated with a hydraulic jump in the channel-lobe transition zone may be the main reason for mud-clasts and matrix addition to the flow. The large-scale addition of mud-clasts and suspended mud may dampen turbulence in proximal to medial lobe settings, and result in medium-to thick-bedded HEBs with common erosional features and tripartite structures. The remaining suspension flow (with abundant mud) may further transport down-dip and form medium-to thin-bedded HEBs with bipartite structures and rare mud-clasts. These findings may be applicable to other SSGF systems with supercritical flow deposits and hybrid event beds, emphasizing the downdip and lateral variation in depositional elements associated with gravity flow evolution.
... Diante dessas diferentes circunstâncias, nós sugerimos que os ofiuroides do grau A3 poderiam ter sido soterrados por sedimentos remobilizados tanto por fluxos hiperpicnais como por ondas de tempestades, além de uma combinação de ambos os processos. Mesmo assim, é bastante provável que fluxos hiperpicnais tenham tido uma influência dominante na geração dos leitos A3, levando em consideração que podem transportar grandes volumes de água doce intersticial (Figura 9C-D) e que são muito aptos em difundir lamas fluidas para zonas distais em bacias marinhas epicontinentais (Figura 9A) (Zavala et al. 2012;Zavala & Arcuri, 2016;Otharán et al., 2018;Zavala, 2020). Esse contexto deposicional é representado aqui pela alta proporção de ofiuroides do grau A3 preservados em leitos tipicamente maciços de argilito e siltito arenoso, (Müller, 1979). ...
... Interessantemente, os segmentos de braço de ofiuroides ao longo dos leitos B1 também (Zavala & Arcuri, 2016;Zavala, 2020 Allison, 1990;Kerr & Twitchett, 2004;Gorzelak & Salamon, 2013 -de forma relativamente similar ao padrão descrito na primeira amostra (Figura 24B (Donovan, 1991;Brett et al., 1997;Ausich, 2021). Dessa forma, é altamente improvável que apenas alguns segmentos de braço sejam propensos a permanecer totalmente articulados por um período mais longo do que os outros braços dentro de uma mesma carcaça de ofiuroide. ...
Thesis
Due to the low preservation potential of their multi-elemental skeletons, articulated ophiuroid fossils can be used as an accurate taphonomic guide to exceptional fossilization conditions. Based on this principle, the objective of this work is to investigate the taphonomic history of ophiuroids-producing beds across three paleontological sites in eastern Paraná state, Brazil, where epicontinental Devonian sequences from the Ponta Grossa Formation are well represented. Through fieldwork, tomographic analysis, and description of 218 samples, five taphonomic grades were listed to represent the depositional histories of these ophiuroid beds in the Ponta Grossa Formation. Three high-order taphonomic grades (A1-A3) reflect ophiuroids suddenly buried in life. Grade A1 encompasses sparse skeletons of ophiuroids articulated and oriented in normal postures, parallel to the bedding planes. Grade A2 groups clusters of articulated ophiuroids oriented in specific horizons, sometimes with specimens in inverted postures. Grade A3 comprises complete to incomplete skeletons of ophiuroids in escape postures, inclined at low angles in the bedding planes, occasionally with evidence of autotomized arms. In turn, two lower-order taphonomic grades (B1-B2) include a limited number of disarticulated skeletons, reflecting ophiuroid specimens buried between hours to a few days after death. Grade B1 consists of disarticulated ophiuroids in a normal post-mortem degradation sequence, with arms tips absent or dissociated close in the sediment. Grade B2 combines ophiuroids in a selective disarticulation pattern, with the mixing of intact segments and dissociated portions in the sediment, suggesting macrobenthic disturbance of the carcasses. These records indicate that fluvial discharges were the primary burial mechanisms for ophiuroids in the Ponta Grossa Formation, as they can transport large loads of freshwater-rich sediment to distal zones of marine basins, favoring mass dormancy of errant echinoderms. Meanwhile, storms were probably only a subordinate burial process, given that they remobilize sediments without a key anesthetic. Furthermore, with the aid of scanning electron microscopy, carbonaceous compressions were recorded for the first time in fossil echinoderms, highlighting the kerogenization of visceral organs of the disk of some ophiuroids, apparently with associated pyritization. Considering the association with varied lithotypes and benthic communities, it is likely that ophiuroids have thrived in different seabeds along the Ponta Grossa Formation, although being preserved only under a restricted taphonomic window, especially in distal marine regions free from the interference of waves, currents, and bioturbators. This preservation window seems to have been potentiated in regressive systems due to the gradual increase in fluvial influence over the ancient epicontinental sea of the formation. Therefore, because of the presence of exceptionally articulated ophiuroids with preserved organic remains, the Ponta Grossa Formation can be adequately classified as a echinoderm Konservat-Lagerstätte from the Devonian of Brazil.
... The lower portions of even finer-grained turbidites (Ta divisions) such as those in the Ross Sandstone Formation are organically-lean, although mud-chips and associated OM may preferentially segregate in the lee side of the ripple-laminated divisions sandstones as shown in Figure 3d in [11]. Nevertheless, a limited number of studies have described organic-rich layers in sandy deepsea turbidites [1,10,[84][85][86], in some cases even within sands of units Ta and Tb (Figure 3b,c), depending on the density and size of organic debris [1,12]. Fine-to very fine-grained Miocene turbidite sandstones in Kutei Basin, Indonesia contain significant quantities of organic carbon (average TOC in Tb division = 8%) in the form of terrestrial leaves and coaly fragments (Figure 3b,c) [1]. ...
... Woody material has been reported in turbidities from multiple locations such as Gres d'Annot, southeast France and the Marnoso-Arenacea Formation, Italy [12,13], as well as sands in the Bengal Fan in the Indian Ocean [86] and in the Bute Inlet Fjords [10]. Other examples of plant material transported into deep-water marine settings via hyperpycnal flows (direct river discharge) are known from Eocene rocks exposed within the Central Basin of Spitsbergen, Norway [87] and sedimentary basins in Argentina and Trinidad [84]. These studies suggested that one criterion for recognizing hyperpycnal flow turbidites is the presence of continental plant material within the deposits. ...
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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.
... The hyperpycnal flow is recently attracting significant research attention. Zavala et al. explored the formation conditions, the dynamic characteristics, the sedimentary processes, and sedimentary principles of hyperpycnal flow and established a deposition model for the flow ( [24,25], 2011; [26][27][28][29][30]). In addition, the new technology of formation physical simulation research and engineering stress technology has provided technical support for the effective and economic development of tight oil and gas reservoirs [31][32][33][34][35][36]. ...
Article
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The Chang 7 interval of the Upper Triassic Yanchang Formation in the Ordos Basin represents a typical deep lacustrine depositional sequence. On the basis of field outcrops, cores, well logs, light/heavy mineral provenance analysis, and petrological studies, we evaluated the characteristics of deep-water gravity flow deposition of the Chang 7 interval and constructed a depositional model. The sediments mainly came from the northeast of the study area, and multiple sublacustrine fans were deposited in the center of the basin. Different from the deep-marine fan, the sublacustrine fan in the study area develops under the background of gentle slope without any erosional canyon between the fan and delta front. Gravity flow deposits in the study area can categorised into three groups: sand debris flow deposits, turbidity current deposits, and deep-water mudstone deposits. The main channel and branch channel are mainly developed with thick massive sandy debris sandstone, while the channel lateral margin and branch channel lateral margin are mainly developed with middle massive sandy debris sandstones and turbidite sandstones, which from bottom to top, the thickness of sand layer becomes thinner and the grain size becomes smaller. Thin mudstone is developed between channels; the lobe fringe includes sheet-like turbidite sandstones and deep lake mudstones. The widely distribute, good quality source rocks (TOC=2%–6%) developed in deep lacustrine have attained the peak stage of oil generation (Ro=0.9%–1.2%). The superimposition of the sublacustrine fan sand bodies and the wide distribution of good quality source rocks favor the formation of large lithologic reservoirs characterized by source–reservoir integration, self-generation and self-storage, and near-source accumulation.
... Our study shows that the deep lake succession in the Lucaogou Formation contains stacked deposits emplaced by a number of flow types, including high-density turbidity currents, low-density turbidity currents, and hybrid flows. No terrestrial plant debris or tree trunks were observed in the turbidites or hybrid event beds, which precludes a hyperpycnite origin (Zavala and Arcuri 2016). The distal turbidites and hybrid event beds described here probably evolved from proximal slumps triggered by unstable topography, storms, or earthquakes rather than a hyperpycnal flow. ...
Article
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Submarine or sub-lacustrine lobe deposits are important reservoirs, but the fan fringe deposits form heterogeneities within deep water fan deposits. Fan fringe facies records the complex sediment gravity flow types. By understanding of the bed types and flow mechanisms, we can identify the fan fringe deposit, which aids in the reconstruction of deep water fan and reservoir evaluations. The Jiucaiyuanzi and Dalongkou sections in the West Bogda Mountains preserve well-exposed 536-m and 171-m thick successions, respectively, of a deep water lacustrine depositional system from the Middle Permian Lucaogou Formation. Bed types of the Lucaogou Formation include high-density turbidite, low-density turbidite, incomplete Bouma-type turbidite, hybrid event beds, and slump deposits. The Lucaogou Formation is interpreted here as a fan fringe facies due to the thin bed thickness that characterize turbidites and hybrid event beds, as well as the predominance of the isolated sheet architecture. Previous studies suggest that these deposits were considered as deposited in a deep water setting due to the absence of wave-related structures. The presence of abundant mud clasts in massive medium-coarse grained sandstone beds reflects the significant erosional capability and interactions between high-density turbidity currents and lake floor. The fan fringe facies here contains amalgamated and thick-bedded homolithic facies (~ 30%) and thin-bedded heterolithic facies (~ 70%). The examination of the bed type is of wider significance for facies prediction and reservoir heterogeneity in the sub-lacustrine fan fringe facies.
... Mulder et al. (2003) expanded the applicability of the concept of hyperpycnal plumes from shallow water (deltaic) to deep-water (continental slope and abyssal plain) environments. In this new development, hyperpycnal flows are considered analogous to turbidity currents in many respects (Mulder et al., 2003;Steel et al., 2016;Zavala and Arcuri, 2016). ...
Article
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This review covers 135 years of research on gravity flows since the first reporting of density plumes in the Lake Geneva, Switzerland by Forel (1885). Six basic types of gravity flows have been identified in subaerial and suaqueous environments. They are: (1) hyperpycnal flows, (2) turbidity currents, (3) debris flows, (4) liquefied/fluidized flows, (5) grain flows, and (6) thermohaline contour currents. The first five types are flows in which the density is caused by sediment in the flow, whereas in the sixth type, the density is caused by variations in temperature and salinity. Although all six types originate initially as downslope gravity flows, only the first five types are truly downslope processes, whereas the sixth type eventually becomes an alongslope process. (1) Hyperpycnal flows are triggered by river floods in which density of incoming river water is greater than the basin water. These flows are confined to proximity of the shoreline. They transport mud, and they do not transport sand into the deep sea. There are no sedimentological criteria yet to identify hyperpycnites in the ancient sedimentary record. (2) A turbidity current is a sediment-gravity flow with Newtonian rheology and turbulent state in which sediment is supported by flow turbulence and from which deposition occurs through suspension settling. Typical turbidity currents can function as truly turbulent suspensions only when their sediment concentration by volume is below 9% or C < 9%. This requirement firmly excludes the existence of 'high-density turbidity currents'. Turbidites are recognized by their distinct normal grading in deep-water deposits. (3) A debris flow (c. 25-100%) is a sediment-gravity flow with plastic rheology and laminar state from which deposition occurs through freezing en masse. The terms debris flow and mass flow are used interchangeably. General characteristics of muddy and sandy debrites are floating clasts, planar clast fabric, inverse grading, etc. Most sandy deep-water deposits are sandy debrites and they comprise important petroleum reservoirs worldwide. (4) A liquefied/fluidized flow (>25%) is a sediment-gravity flow in which sediment is supported by upward-moving intergranular fluid. They are commonly triggered by seismicity. Water-escape structures, dish and pillar structures, and SSDS are common. (5) A grain flow (c. 50-100%) is a sediment-gravity flow in which grains are supported by dispersive pressure caused by grain collision. These flows are common on the slip face of aeolian dunes. Massive sand and inverse grading are potential identification markers. (6) Thermohaline contour currents originate in the Antarctic region due to shelf freezing and the related increase in the density of cold saline (i.e., thermohaline) water. Although they begin their journey as downslope gravity flows, they eventually flow alongslope as contour currents. Hybridites are deposits that result from intersection of downslope gravity flows and alongslope contour currents. Hybridites mimic the "Bouma Sequence" with traction structures (Tb and Tc). Facies models of hyperpycnites, turbidites, and contourites are obsolete. Of the six types of density flows, hyperpycnal flows and their deposits are the least understood.
... For the larger events studied in detail, like event 2 in U-Channel 4 (~10 cm) and the event in U-Channel 6 (~20 cm), we find an earthquake/tsunami origin the most straightforward interpretation, given the complex turbidite base, microfracturing and evidence for ongoing oscillations. Contrarily, for less well-resolved, smaller events like event to look in more detail to organic content within the sedimentary events (Zavala and Arcuri, 2016). ...
Preprint
A major challenge in subaqueous paleoseismology is to understand the relationship between an earthquake/tsunami and a sedimentary event deposit recorded in drillcores. Expedition 381 of the International Ocean Discovery Program was dedicated to understanding the development of the Corinth Rift, Greece. Its drilled cores provide a potentially important resource to better understand depositional mechanisms of sedimentary event deposits within changing open marine to (semi-)isolated environments. To achieve this, we analyse U- channels and spatula samples from the topmost part (0-65 m below seafloor maximum depth) of holes M0078B and M0079A (~0-25 ka), using high-resolution X-Ray microtomography in combination with grain-size, magnetic and XRF measurements. Structures and grain array are resolved down to 10 μm in voxel size, characterizing the geometry of the basal surface of turbidite+homogenite sedimentary event deposits, and the internal base-upwards evolution at high-resolution scale. Our analysis suggests these types of deposits are more complex than previously proposed, especially at the transition between the basal coarse turbidite sub-unit and the fine-grained homogenite upper sub-unit, as well as within the homogenite. Combined with the other observations and parameters, X-ray microtomography results are consistent with the interpretation of the Corinth turbidite+homogenite deposits as having predominantly originated from seismic and/or aseismic slope failures followed by tsunami/seiche effects, despite subtle differences according to depositional environment.
... This is more conducive to the development of hyperpycnal flow (Fig. 9). Moreover, because the flow properties of hyperpycnal flow are partly similar to those of the drainage system, it retains a weak traction current (Mulder and Syvitski., 1995;Mulder et al., 2003;Zavala et al., 2006Zavala et al., , 2011Zavala et al., , 2012Zavala et al., , 2014Zavala et al., , 2016. However, coarser clastics that are poorly sorted are carried into the fault-bounded margin by flood flow and form a nearshore subaqueous fan (Fig. 10h). ...
Article
The boundary fault of the Dongying Sag is divided into isolated and scattered segments and small-scale relay zones, which are important geomorphic features controlling sedimentation in the early stage of rift evolution. Previous studies have shown changes in facies in deposits of thousands of meters in thickness on fault-bounded margins, where deep-water fan systems are vertically stacked with delta deposits in the same way as in many basins around the world. However, changes in sedimentation processes and sedimentary systems and their relationship with the evolution of the main boundary fault remain a matter of debate. We focus on the transition from shallow-water to deep-water systems and their responses to relay-ramp evolution in the Yanjia Subsag of the Eocene Dongying Sag in the Bohai Basin. A relatively simple assemblage of local structures provides an ideal opportunity to investigate the impact of relay-ramp evolution on the early synrift deposits. An integrated dataset of 3D seismic volumes, cores and wireline logs is used to analyze the evolution of the Chennan Fault, to delineate thirteen lithofacies, and to recognize two depositional styles (including fan deltas and nearshore subaqueous fans) and their distribution during different stages of the relay-zone evolution. In the early stage of rifting, the depositional style changes, from the development of axial and transverse systems in the early to middle period to the development of transverse systems in the late period; this is mainly controlled by the evolution of the relay ramp. The change is accompanied by a rapid decrease in the rate of sediment supply, architectural changes in transport conduit from the relay ramp to a canyon, and local geomorphic changes that control transport routes, sediment delivery, and depositional locations. Floods ultimately become dominant transport mechanism with a new system, such that hyperpycnal flows form, leading to another transformation of the sedimentary systems from a fan-delta system to a nearshore subaqueous fan system. On the basis of these transformations in sedimentary systems we are able to propose new recommendations for reservoir exploration in continental rift basins, which include exploration potential, source reservoir cap assemblage, and spatiotemporal evolution of plays.
... Low-bioturbated massive siltstones (SIFA-2) could be interpreted as the background offshore sedimentation mostly deposited by slow suspension settling or fallout sedimentation under low-energy conditions linked (1) to hypopycnal flows from suspension clouds related to delta plumes during periods of low river discharge or (2) to flow lofting at distal/off-axis marginal position of the hyperpycnal system Zavala and Arcuri, 2016). Highly bioturbated packages with Nereites and Phycosiphon assigned to the Nereites ichnofacies, could reveal punctual increase of benthic food and good oxygenation on the sea-floor or within the first centimeters of the substrate. ...
Article
Hyperpycnal flows have been widely described in different lacustrine and marine environments but sedimentary structures and fossil content in hyperpycnites often offer limited information about the palaeoenvironmental conditions. This limitation can be improved by ichnological analysis, which has been recently used as a tool to differentiate between different type of subaqueous deposits, even though still only a few detailed ichnological studies on hyperpycnites exist. In order to bridge this gap in knowledge, a 50 m-thick package of terrestrial organic debris-rich, dominantly structureless and well-sorted sandstone bodies alternating with burrowed siltstones (Upper Miocene, Betic Cordillera, Spain) is here analyzed. This study is based on observations of a well-exposed outcrop and cores from a well drilled just behind the outcrop to bridge field-scale observational gaps. Two type of sandbodies were typified on the basis of their stratigraphic architecture, physical sedimentary structures, and ichnofacies in the fine-grained deposits embedding them: (1) Lobate to channelized-top sandstones embebbed into silty sands with dominant highly variable degree of bioturbation by Taenidium and Schaubcylindrichnus (depauperate Cruziana ichnofacies) and interpreted as proximal marine sustained hyperpycnites in prodelta settings; and (2) channelized-lobate (cut-and-fill sequence) sandstones embebbed into siltstones with dominant Nereites and Phycosiphon (Nereites ichnofacies) interpreted as distal hyperpycnites developed in offshore settings. The studied succession is interpreted to represent the progradation of a sandy hyperpycnal system along a prodelta to starved offshore setting with high variability in grain-size, benthic food and oxygen content. Results of this study suggest that a multi-scale analysis focused on trace fossils and physical sedimentary signatures is needed to get a better understanding of these river-derived sustained-flow turbidites (hyperpycnites) that are less well known than their conventional surge-type turbidite counterparts.
... The Palaeoproterozoic Liaohe Group is such an ancient complicated rock association in the eastern NCC . According to a comparison with the modern marine depositional tectonic setting (Huppertz and Piper, 2010;Zavala and Arcuri, 2016), we propose that the Gaojiayu Formation was deposited within an abyssal and semi-abyssal turbidite depositional environment. ...
Article
The Palaeoproterozoic sedimentary environment is difficult to reconstruct because rocks often experience multiple stages of deformation and metamorphism; however, it is critical to understand the Precambrian evolution of sedimentary basin. In this study, we report two un-metamorphosed sections in the Gaojiayu Formation of the North Liaohe Group, central part of the Jiao-Liao-Ji orogenic belt, eastern North China Craton. Rocks consist of shales, carbonaceous slates, calcareous mudstones and sandstones, marlstones, calcarenites, and brecciated limestones in these sections. Detailed field observations indicate that all kinds of original bedding and syn-depositional structure developed in these rocks. Microscope observations suggest that detritus in rocks predominantly contain feldspars, quartz, and calcites, occasionally with volcanic fragments and pyrites. Palaeocurrent study indicates that the provenance of detritus in rock of these two sections was from NW to SE. Detrital heavy minerals mainly consist of pyrite and hematite, occasionally with barite, which are all from the Li'eryu Formation that contains these minerals in sedimentary layers. The increase of percentages of pyrite in a cross-section indicate that the sedimentary environments transformed from an oxidizing to a reducing depositional environment because the depositional setting became deeper. According to the mafic intrusion dated in this study and regional geochronological data such as the age of underlying volcanic rocks, the depositional age of the Gaojiayu Formation is constrained between 2.17 and 2.16 Ga and 2.11 Ga. Archaean basement (2.5 Ga) is recognized as the major provenance providing clastic materials for the Gaojiayu Formation; volcaniclastic rocks in the Li'eryu Formation were also a significant source. Accordingly, in this paper we interpret the Gaojiayu Formation as turbiditic sedimentary rocks that were deposited in an arc-related abyssal and semi-abyssal environment, probably in an extensional back-arc basin setting. Palaeoproterozoic turbidite deposition combined with a 2.17 Ga volcanic arc developed in the study area, we conclude that the modern trench-arc-basin system may had already existed in the early Palaeoproterozoic and deeply affected the tectonic evolution of the Jiao-Liao-Ji orogenic belt, northeastern North China Craton.
... The fluvial system recorded in the upper interval lacks both evidence of lateral accretion and overbank deposits, suggesting low-sinuosity braided channels. Participation of hyperpycnal flows is suggested by the presence of massive sandstone, most likely recording high sedimentation rates and gradual collapse from a turbulent flow (Zavala and Arcuri, 2016). Flow velocity and acceleration reach their maximum at the axial zone and diminishes progressively towards the distal areas (Zavala et al., 2006). ...
Article
The Upper Cretaceous M2 and U Sandstone members of the Napo Formation are prolific hydrocarbon producers in the Oriente Basin of eastern Ecuador. To understand the depositional origin of these reservoirs, an integrated sedimentologic, sequence-stratigraphic, and ichnologic study, using 490 ft (∼149 m) of conventional core from six wells of oil fields located in the eastern part of the basin, was performed. Sedimentary facies, stratal stacking pattern, discontinuity surfaces, and trace fossils were documented. Nine lithofacies and two depositional sequences in each member were identified. Three main broad environments, fluvial, estuarine and deltaic, have been interpreted. Trace fossils are very rare in the fluvial deposits and comprise facies-crossing ichnotaxa. The trace-fossil association of estuarine deposits is of low diversity containing ichnotaxa indicative of marine influence (e.g. Asterosoma, Teichichnus). In comparison, deltaic deposits display higher ichnodiversity, and are more intensely bioturbated, locally including some ichnotaxa (e.g. Zoophycos) that suggest the system may have experienced fully marine conditions sporadically. Controlling factors are typically expressed differently in the various subenvironments as a result of the interplay of tides and river discharge. The most important stress factors were substrate type and consistency, episodic sedimentation, high energy, water turbidity, and changes in salinity. Our integrated approach may prompt similar studies in other hydrocarbon-bearing units in Ecuador.
... Our study shows that the deep lake succession in the Lucaogou Formation contains stacked deposits emplaced by a number of flow types, including high-density turbidity currents, low-density turbidity currents, and hybrid flows. No terrestrial plant debris or tree trunks were observed in the turbidites or hybrid event beds, which precludes a hyperpycnite origin (Zavala and Arcuri 2016). The distal turbidites and hybrid event beds described here probably evolved from proximal slumps triggered by unstable topography, storms, or earthquakes rather than a hyperpycnal flow. ...
Article
Full-text available
Submarine or sub-lacustrine lobe deposits are important reservoirs, but the fan fringe deposits form heterogeneities within deep water fan deposits. The identification of fan fringe deposits can aid in the reconstruction of deep water fan and reservoir evaluations. Fan fringe facies records the complex sediment gravity flow types. By understanding of the bed types and flow mechanisms, we can identify the fan fringe deposit. The Jiucaiyuanzi and Dalonggou sections in the West Bogda Mountains preserve well-exposed 536-m and 171-m thick successions, respectively, of a deep water lacustrine depositional system from the Middle Permian Lucaogou Formation. Bed types of the Lucaogou Formation include high-density turbidite, low-density turbidite, incomplete Bouma-type turbidite, hybrid event beds, and slump deposits. The Lucaogou Formation is interpreted here as a fan fringe facies due to the thin bed thickness that characterize turbidites and hybrid event beds, as well as the predominance of the isolated sheet architecture. Previous studies suggest that these deposits were considered as deposited in a deep water setting due to the absence of wave-related structures. The presence of abundant mud clasts in massive medium-coarse grained sandstone beds reflects the significant erosional capability and interactions between high-density turbidity currents and lake floor. The fan fringe facies here contains amalgamated and thick-bedded homolithic facies (~30%) and thin-bedded heterolithic facies (~70%). The fan fringe facies forms heterogeneities. The examination of the bed type is of wider significance for facies prediction and reservoir heterogeneity in the sub-lacustrine fan fringe facies.
... The abundance of platy micas and amorphous organic matters could be linked to a terrigenous origin (Saller et al., 2006). The mudclast type thus could be less likely to be incorporated from initial slope failures, but it may be largely attributed to erosion of underlying flood-related, plume-generated turbidites and even organic-rich debrites (Zavala and Arcuri., 2016;Hage et al., 2019;Zavala, 2020;Hussain et al., 2021) via successive turbidity currents (Fig. 19a), which occurred prior to the occurrence of flow transformation. The comparatively lower cohesive mud content suggests that the mudclast type contributed less to the formation of HEBs through mud-driven flow transformation. ...
Article
Hybrid event beds (HEBs) record disequilibrium in submarine fan evolution attributed to mud-forced dampening turbulence, which could be caused by allogenic and autogenic forcings in either the proximal or distal segment of a lobe-dominated submarine fan on several timescales. Detailed field investigation combined with petrographic and mineralogical analysis of selected outcrop samples indicate that the Upper Triassic submarine fan succession mainly comprises turbidites, HEBs, and debrites in the West Qinling (WQ) area of NE Tibetan Plateau. Five types of HEBs are recognized based on the thickness, sedimentary structure, and texture. Bed-by-bed description and measurement reveal that these HEBs show a distinct distribution pattern throughout the submarine fan succession, including dominance of HEB-1 and HEB-2 beds (∼71.50%) in distributary channel to lobe off-axis (FA1–FA3) and significant portion of HEB-3 to HEB-5 beds (∼54.22%) in lobe fringe to lobe distal fringe environments (FA4–FA5). Textural and petrographic characteristics of mudclasts suggest disaggregation of heterolithic, homogenous and less cohesive mudclasts (MC-1 to MC-4 type) within H1b and H3 interval of HEBs, which could play different roles in the longitudinal mud-driven flow transformation between turbulent and laminar flow behavior patterns. The vertical distributions of the HEB-prone succession are characterized by four types of depositional scenarios, which yields significant allogenic and autogenic signatures combined with the recognition of the dominant HEB types and thickening- or thinning-upward trend of the vertically stacked submarine lobes. This study can enhance our understandings of flow transformation of sediment gravity flows (SGF) along the eastern margin of the Paleo-Tethys Ocean based on the anatomy of several undiscovered deep-water outcrops, which were reflected by the initiation, gradual switching, and avulsion of the high-frequency submarine fan evolution during the Late Triassic.
... Slumps, for instance, may transform into cohesive debris flows, and such debris flows may change back into slumps (Wang et al., 2020), but debris flows may also evolve into intrabasinal turbidity currents (Zavala and Arcuri, 2016), which most commonly take place in the middle to upper part as well as in the tail of the flow. This is because debris flows entrain ambient water and gradually become more diluted (Sumner et al., 2009;Bernhardt et al., 2012). ...
Chapter
Research into transport and deposition mechanisms of fine-grained mass-flow deposits is hampered by the absence of an easily applicable classification scheme. We propose here such a scheme on the basis of the mud content in combination with the presumed transport mechanism. The scheme comprises 12 types of gravity-flow deposits. The practical applicability of this classification is shown for the Triassic lacustrine Yanchang Formation in the Southern Ordos Basin (China). This formation contains abundant slump deposits, debrites, turbidites, and hyperpycnites. The analysis of the fine-grained gravity-flow deposits indicates that (1) mud can be deposited under active hydrodynamic conditions; (2) lacustrine mudstones and shales consist in a large part of gravity-flow deposits; (3) fine-grained gravity flows contribute much to the transport and deposition of organic matter, and thus are important mechanisms involved in the generation of hydrocarbons; (4) the mechanisms of transport and deposition, and consequently the resulting sorting, largely determine the reservoir capability of fine-grained gravity-flow deposits.
... There is increasing evidence of a direct and abundant supply of sediment from rivers in flood to the inner basin via hyperpycnal flows (Zavala & Arcuri, 2016), providing new perspectives for the understanding of fluvio-deltaic system. Frequent tectonic movements and earthquakes, large topographic slope, seasonal floods and typhoons are the main controlling factors for triggering hyperpycnal flow (e.g., Mulder & Syvitski, 1995;Mutti et al., 2003;Plink-Björklund & Steel, 2004;Zavala et al., 2006). ...
Article
Volcanic eruptions can provide large amounts of sedimentary materials and expose fluvial valleys or lakes to catastrophic hyperpycnal flood events, but this process has not been documented in detail. The Ordos Basin Permian fluvio-deltaic system reveals evidence for abundant volcanism linked to the tectonic evolution of orogenic belt around the basin and provides a ‘natural laboratory’ for investigating hyperpycnal flows associated with volcanic activity. This study analysed volcanic matrix-rich sandstone (VMS) samples for petrology, mineralogy and geochemistry in order to address current and uncertain volcanogenic material provenance explanations and the lack of systematic investigations into the depositional and diagenetic processes of volcanic related sediments in the southwestern basin. By combining tectonic background surveys, detrital zircon geochronology and spatial distribution of volcanogenic materials, it was found that volcanogenic materials were not derived from the Yinshan-Yanshan Orogenic Belt (YYOB) as previously thought, but instead evidence a southwestern origin from the North Qinling Orogenic Belt (NQOB). Volcanogenic materials retained in the provenance area during frequent volcanic eruptions were transported to the basin via fluvial system shortly after eruption. The associated sediments meet the criterion for hyperpycnites based on lithofacies associations, suggesting the occurrence of hyperpycnal flows during the deposition of VMS. During the subsequent burial stage, the VMS became three distinct types defined by their volcanic matrix content and have similar paragenetic sequences but different diagenetic intensities. The differing content of authigenic minerals in the three types was closely related to the sandstone pore structure characteristics and the evolution of volcanic-matrix alteration materials. This article proposes a possible explanation for the previously unidentified tectonothermal events in the NQOB during the Permian, validating and reinforcing theoretical work of hyperpycnal flow. This contribution provides new insights and understanding of the depositional and diagenetic processes of lacustrine basins with similar tectonic settings.
... Due to its relative high 553 bulk density, the river discharge plunges and bypass 554 coastal areas generating a coastal-detached subaqueous 555 channel-lobe system (Zavala and Pan 2018). The associ-556 ated deposits show the characteristics of extrabasinal 557 turbidites (Zavala and Arcuri 2016). In brackish (lacus-558 trine or marine) settings, the density threshold to gener-559 ate HSD is easily achieved by most dirty rivers (Fig. 2). ...
Article
Full-text available
Deltas constitute complex depositional systems formed when a land-derived gravity-flow (carrying water and sediments) discharges into a marine or lacustrine standing body of water. However, the complexity of deltaic sedimentary environments has been oversimplified by geoscientists over the years, considering just littoral deltas as the unique possible type of delta in natural systems. Nevertheless, a rational analysis suggests that deltas can be much more complex. In fact, the characteristics of deltaic deposits will depend on a complex interplay between the bulk density of the incoming flow and the salinity of the receiving water body. This paper explores the natural conditions of deltaic sedimentation according to different density contrasts. The rational analysis of deltaic systems allows to recognize three main fields for deltaic sedimentation, corresponding to (1) hypopycnal (2) homopycnal and (3) hyperpycnal delta settings. The hypopycnal delta field represents the situation when the bulk density of the incoming flow is lower than the density of the water in the basin. According to the salinity of the receiving water body, three different types of hypopycnal littoral deltas are recognized: hypersaline littoral deltas (HSLD), marine littoral deltas (MLD), and brackish littoral deltas (BLD). The basin salinity will determine the capacity of the delta for producing effective buoyant plumes, and consequently the characteristics and extension of prodelta deposits. Homopycnal littoral deltas form when the density of the incoming flow is roughly similar to the density of the water in the receiving basin. This situation is typical of clean bedload-dominated rivers entering freshwater lakes. Delta front deposits are dominated by sediment avalanches. Typical fallout prodelta deposits are absent or poorly developed since no buoyant plumes are generated. Hyperpycnal deltas form when the bulk density of the incoming flow is higher than the density of the water in the receiving basin. The interaction between flow type, flow density (due to the concentration of suspended sediments) and basin salinity defines three types of deltas, corresponding to hyperpycnal littoral deltas (HLD), hyperpycnal subaqueous deltas (HSD), and hyperpycnal fan deltas (HFD). Hyperpycnal littoral deltas are low-gradient shallow-water deltas formed when dirty rivers enter into brackish or normal-salinity marine basins, typically in wave or tide-dominated epicontinental seas or brackish lakes. Hyperpycnal subaqueous deltas represent the most common type of hyperpycnal delta, with channels and lobes generated in marine and lacustrine settings during long-lasting sediment-laden river-flood discharges. Finally, hyperpycnal fan deltas are subaqueous delta systems generated on high-gradient lacustrine or marine settings by episodic high-density fluvial discharges.
... Hyperpycnal flows are recognized as an effective mechanism for the basinward transport of freshwater and plant debris for long distances during floods (Mulder et al., 2003). Those "extrabasinal turbidites" (see Zavala and Arcuri, 2016) show characteristic sedimentary arrangements (not discussed here) where plant remains occur in most of their facies (Ponce and Carmona, 2011a,b;Zavala et al., 2012). In this regard, global studies focused on the palynological content of hyperpycnites are relatively scarce (Carrillo-Berumen et al., 2013;Martínez et al., 2016;Mignard et al., 2017;Slater et al., 2017;Quattrocchio et al., 2018). ...
Article
The basal succession of the Lajas Formation at Trasandino section, Arroyo Covunco area, constitutes an excellent example of proximal prodelta facies cut by sediment-waves formed during a complete acceleration-deceleration hyperpycnal discharge cycle. The main outcome of this contribution was to present a new studied locality in which the Lajas Formation outcrops. Nine mudstones and fine-grained heterolites levels deposited during the waning stage, were sampled to palynological analysis. The recovered assemblages are dominated by sporomorphs, which are characterized by a great diversity of the trilete spores. Among them, is interesting to highlight the first mention of Manumia variverrucata and the extension of the last occurrence of Striatella seebergensis until to Callovian in Argentina. Based on selected key taxa a Late Bathonian–Callovian age is proposed for the Lajas Formation at the Trasandino section in this area. The Trasandino section spore assemblages show the greatest similarity with the Arroyo Covunco section spore associations when they are compared with the Lajas Formation of other studied localities. The endemic development of certain types of bryophyte (sensu lato) spores, e.g. Taurocusporites quattrocchiensis, was favored by locally humid conditions inferred at the Arroyo Covunco area. Large abundance of phytoclasts, sporomorphs and fresh-water algae characterize the recovered organic matter suggesting a high input of continental organic particles to the basin, as the result of fluvial-derived density discharges. Three palynofacies type (PT) had been identified which allow to evaluate the hydrodynamic characteristics of the flow, taking into account the differential buoyancy of the opaque particles. The large amount of equidimensional opaque particles recognized at the PT-B, characterizes the beginning of the deceleration phase of the flow and the abundance of blade-shape opaque particles, identified in the PT-A, point out a deposition from the final buoyant plume of hyperpycnal flow. The PT-C shows transitional features between these two conditions.
... Cowan et al., 1997Cowan et al., , 1998Cowan et al., , 1999Milleson et al., 2016;Fedorchuk et al., 2019b;Tedesco et al., 2020). However, rhythmites also occur in numerous non-glacial environments including lake, tidal flat, estuary, delta (e.g., hyperpycnites), and deep-marine (e.g., turbidites and contourites) settings (e.g., Kuenen and Migliorini, 1950;Martino and Sanderson, 1993;Greb and Archer, 1995;Zolitschka et al., 2015;Zavala and Arcuri, 2016;Shanmugam, 2018). In part, bioturbation is inhibited or greatly reduced in abundance in some of these glacial and non-glacial settings because of high sedimentation rates (cf. ...
Article
The late Paleozoic Ice Age (LPIA) was one of Earth's most important Phanerozoic climatic events lasting for over 100 Mys. Despite its importance, its history is controversial with two hypotheses that portray glaciation differently (Fig. 1). Traditional views characterize the LPIA as a continuous glacial event that lasted from the Middle Mississippian until the Late Permian with a massive ice sheet that covered Gondwana throughout this interval. This approach often uses only one or two proxies to define the glaciation. The other emerging hypothesis suggests that numerous ice sheets occurred in Gondwana with individual glacial events lasting up to 10 Mys alternating with glacial minima/non-glacial intervals of similar duration. Both views are still prevalent. Both near and far-field proxies are used to define the ice age. Near-field proxies include the occurrence/absence of diamictites, glaciotectonic deposits/landforms, striated clasts and clast pavements, outsized clasts (dropstones), rhythmites, cyclic diamictite-bearing successions, glendonites, grooved and striated surfaces, streamline landforms, and U-shaped paleovalleys. Detrital zircons and chemical index of alteration (CIA) studies help to delineate the occurrence, extent, and location of glaciation. Multiple complexities occur with the use of these proxies as different non-glacial processes and driving factors can produce similar features or results. Far-field proxies focus on identifying changes in eustacy. These include the occurrence of cyclic successions composed of alternating nonmarine and marine strata (cyclothems), depth of incised valleys, paleotopographic relief, phosphatic black shales, and changing oxygen isotope ratios. Like the near-field record, far-field proxies are complex indicators with varied nuances that make their application challenging. Here we discuss the limitations and use of these proxies and promote a multiproxy approach to investigating Earth's glacial intervals. We suggest that studies incorporate multiple proxies coupled with detailed environmental, paleoflow, and paleogeographic analyses to better constrain the occurrence, timing, and extent of glaciation and its influence on global systems. This approach will provide a robust view of the LPIA. We also consider the magnitude and nature of sea-level response to changing ice volumes by discussing ice-volume fluctuations, basin subsidence's modification of glacioeustacy, and sea-level's response to global isostatic adjustment (GIA). In considering these features, it becomes apparent that glacioeustacy is more complex than previously envisioned.
... Hyperpycnal plume occurs when the discharge river density is higher than the density of reservoir water (Zavala and Arcuri, 2016;Zavala and Pan, 2018). Subsequently, the mixture of sediments and freshwater is directly delivered into the deep-water conglomerate, leaching lithic fragments. ...
Article
A section of the northern Yanjia nearshore subaqueous fan sandy conglomerate was investigated to understand high-quality reservoirs' distribution and controlling factors in the retrogradation and progradation sequences. These conglomerates have been demonstrated to have strong heterogeneity, are tightly cemented, and feature low porosity and permeability. To provide an inclusive understanding of the formation mechanisms and factors governing the distribution of the high-quality reservoirs, we utilized integrated methods including seismic, cores description, wireline, petrography, scanning electron microscopy, cathodoluminescence, and mercury intrusion capillarity. The results showed that the retrogradation rock types are dominated by arkose and lithic arkose and the progradation by lithic arkose and feldspathic litharenite. The dominant diagenesis events are compaction, carbonate cementation, and dissolution. The mechanical compaction effect is similar in the progradation and retrogradation sequence. The average compaction index of 0.70 and 0.68 for the transgressive system tract and highstand system tract, respectively, revealed that compaction is the dominant mechanism in reducing reservoir quality in the nearshore subaqueous fan. The carbonate cementation is more extensive in the highstand system tract than the transgressive system tract. The braided channel sandy conglomerate from transgressive system tract and highstand system tract have the best reservoir quality and features type I and II mercury intrusion capillarity cures with large pore throat and good physical properties. However, the braided channel reservoir quality from the highstand system tract developed during the progradation phase is relatively better than the braided channel of the transgressive system tract in the retrogradation phase. These microfacies are characterized by a substantial dissolution of rock fragments and feldspar. The main channel and the interchannel deposited during the transgressive and highstand system tract, respectively, represented by type III mercury intrusion capillarity curves with small pore throats, are non-reservoirs. The formation mechanism of the high-quality reservoirs in the highstand system tract is guided by sedimentary facies, compaction resistant ability, dissolution of rock fragment, and feldspar. The genetic mechanism of the high quality in the transgressive system tract is governed by the sedimentary facies, compaction resistant ability, carbonate and feldspar dissolution. This study revealed that the progradation sequence retained the favorable high-quality in the nearshore subaqueous fan. This study proved that, for adequate assessment of reservoirs in the Yanjia area and similar reservoirs elsewhere, reservoir characterization must link sequence stratigraphy, sedimentary facies, and diagenesis to comprehend the high-quality reservoir distribution to help the predrill evaluation of reservoirs.
... Moreover, the fans related with these canyons, which have a direct connection to a major fluvial river, are more likely to have sandy sediments that could act as reservoirs for hydrocarbon (Jobe et al., 2011). However, the presence of coarse-grained sediments within the submarine fans is dependent on the fluvial sediment source and littoral currents which may be reaching the canyon head (Moore, 1961(Moore, , 1969Shepard, 1972;Jobe et al., 2011;Zavala and Arcuri, 2016). ...
Article
Submarine canyons are major conduits for sediment transfer from continental shelf to deep marine environments. Mass failures and faults play a key role in the initiation and evolution of submarine canyons along convergent tectonic margins, in addition to continental sediment supply. Here we analyze high-resolution bathymetry and seismic data from the Colombian southern Caribbean to investigate the controls on submarine canyon morphology along a convergent tectonic margin. We propose three end-member types of canyons: Type I canyons have a direct connection to a major river associated with high sediment supply. These canyons are highly erosive and cut topographic barriers created by tectonic deformation. Type II canyons are associated with faults at the canyon's head, where the location, orientation, and sinuosity are controlled by fault strike. Also, the presence of faults is related to an increase in the occurrence of mass failures from the steep canyon borders, increasing the depth and width asymmetry. Finally, Type III canyons evolve toward the continental shelf edge through retrogressive mass failures. These mass failures produce erosional scars that merge downslope to create submarine canyons in early stages of development, which later evolve to wider but shallow canyons due to the progressive basinward merging. We argue that the morphology of each canyon type is controlled by the interaction between continental sediment supply, mass failures, shelf width, and fault occurrence. We also demonstrate that seafloor topography influences the size of submarine fan deposits at the mouths of canyons. We identified large fan deposits (>650 km²) on the continental rise, whereas in piggyback sub-basins we found smaller fans (<60 km²). Our analysis of downdip canyon morphology and associated deposits can be used to predict the development of submarine canyons and associated fans in convergent tectonic margins worldwide.
... As mentioned before (Turbidites and homogenites: brief reminders section), the sharp grain-size breaks within the TuHm deposits can also be interpreted as the result of turbidite lofting (Zavala et al., 2011) or fluid mud layers that hinder the settling of non-cohesive grains (Stevenson et al., 2014). In future work, one possible way to help distinguish the depositional mechanism is to look in more detail to organic content within the sedimentary event deposits (Zavala & Arcuri, 2016). ...
Article
A major challenge in subaqueous palaeoseismology is to understand the relationship between an earthquake/tsunami and a sedimentary event deposit recorded in drillcores. Expedition 381 of the International Ocean Discovery Program was dedicated to understanding the development of the Corinth Rift, Greece. Its drilled cores provide a potentially important resource to better understand depositional mechanisms of sedimentary event deposits within changing open marine to (semi‐)isolated environments. To achieve this, U‐channels and spatula samples were analysed from the topmost part (0–65 m below seafloor maximum depth) of holes M0078B and M0079A (ca 0–25 ka), using high‐resolution X‐ray microtomography in combination with grain‐size, magnetic and X‐ray fluorescence measurements. Structures and grain fabric are resolved down to 10 μm in voxel size, characterizing the geometry of the basal surface of ‘turbidite+homogenite’ sedimentary event deposits, and the internal base‐upward evolution at high‐resolution scale. This analysis suggests that these types of deposits are more complex than previously proposed, especially at the transition between the basal coarse turbidite sub‐unit and the fine‐grained homogenite upper sub‐unit, as well as within the homogenite. Combined with the other observations and parameters, X‐ray microtomography results are consistent with the interpretation of the Corinth ‘turbidite+homogenite’ deposits as having predominantly originated from seismic and/or aseismic slope failures followed by tsunami/seiche effects, despite subtle differences according to depositional environment.
Thesis
Se realizó un estudio multidisciplinario de detalle sobre el tramo basal de la Sección “Don Silverio” perteneciente a la Formación Los Molles, en la Subcuenca de Picún Leufú, Neuquén. El objetivo del presente trabajo es contribuir al conocimiento integral de la Formación Los Molles (Jurásico Temprano-Medio) al sur de la Dorsal de Huincul y evaluar el potencial oleogenético de la sección estudiada. A partir del estudio sedimentológico/estratigráfico, se reconocieron hiperpicnitas fangosas y arenosas depositadas en un Delta Hiperpícnico Subacuático. Este delta se habría desarrollado en porciones distales de la plataforma, por debajo de la acción de oleaje, durante períodos de mayor eficiencia del sistema deltaico. En cuanto al análisis de la materia orgánica palinológica, se reconoció una predominancia absoluta de materia orgánica de origen continental. Un total de 4 palinofacies tipo fueron definidas, las cuales reflejan las diferentes condiciones de depositación y energía presentes en los diferentes flujos hiperpícnicos. En base a la variedad de taxones continentales reconocidos (Cheirolepidiaceae, Araucariaceae, Botryococcaceae, entre otros) y las diferencias de requerimientos paleoecológicos que tienen cada uno de ellos, se evidencia el largo camino y los distintos ambientes que atravesaron los flujos hiperpícnicos hasta alcanzar la cuenca receptora. A partir del análisis geoquímico de las muestras, se reconoce que los valores de carbono orgánico total son mayores al 1% en casi todos los casos, lo que permitiría asociar a estas rocas con buena a muy buena capacidad de generación de hidrocarburos. Sin embargo, los bajos valores obtenidos de S2 no confirman dicha asignación, por lo que finalmente se las clasifica como rocas con pobre potencial. El querógeno presente es de tipo III/IV y IV, constituido por materia orgánica esencialmente rica en carbohidratos de plantas vasculares. La interpretación del potencial oleogenético que se obtiene a partir del análisis palinológico presenta una correlación con los resultados obtenidos a partir del estudio geoquímico, por lo que la sección de estudio no cumple con las condiciones para ser considerada un buen reservorio no convencional de tipo shale gas.
Article
The lacustrine conglomerate reservoirs of the Lijin sag, Bohai Bay Basin, East China, were studied to understand the roles of depositional and diagenetic events on reservoir quality, using integrated seismic data, well logs, core observations, optical petrography, SEM-EDS, cathodoluminescence, and fluid inclusion microthermometry. The results show a fan delta with well-connected conglomerate bodies deposited during a highstand system tract (HST) and a nearshore subaqueous fan with weakly connected conglomerate bodies deposited in a transgressive system tract (TST). The conglomerates are mainly classified as feldspathic litharenite. The porosity and permeability of the fan delta vary from 0.1% to 17.4% and 0.01 to 457.6 mD, respectively. The porosity and permeability vary from 2.02 to 16.2% and 0.02 to 237.2 mD in the nearshore subaqueous fan. Mechanical compaction, dissolution, and cementation together are noteworthy diagenetic processes. Compaction is the dominant factor in reducing porosity; cementation has a destructive effect, while dissolution improves reservoir quality. Feldspar dissolution leads to kaolinite, illite, dickite precipitation, and deteriorating reservoir quality. The probable sources of meteoric water flux in the deep-burial environments are related to the falling lake level during the HST. Fluid inclusion analysis revealed that quartz overgrowths were formed during the mesodiagenetic stage. The depositional environment and grain sizes are essential factors controlling reservoir quality. The effect of grain size and sorting coefficients on reservoir quality varies as a function of retrogradation and progradation sequences. The higher the porosity and permeability, the coarser the particle sizes in the retrogradation sequences. In the progradation sequences, poorly sorted sediments have higher porosity and permeability than well-sorted sediments. The braided channel embodies the best reservoir quality in the TST, while the distributary channel represents the best reservoir in the HST. The formation mechanism of the high-quality reservoirs is ascribed to the sedimentary facies, compaction resistance, and mineral dissolution. Overall, the conglomerate reservoirs developed in the HST are relatively better than those in the TST because they have greater labile fragments, resulting in more dissolution. This study demonstrated that for successful assessment of conglomerate reservoirs in the Lijin area and similar reservoirs elsewhere, reservoirs characterization must link sequence stratigraphy, facies, and diagenesis to understand the high-quality reservoir distribution to support the predrill evaluation of reservoirs.
Article
A 371 m sequence of Pleistocene age turbidites was recovered at ODP (Ocean Drilling Program) Leg 202, Site 1232 at 39°53.45'on the Nazca Plate, seaward of the Peru-Chile Trench. Coarsest sediments within the turbidites (<300 μm) contain large amounts of fresh, angular volcanic glass shards. We investigated the variation in proportions of coarsest (>149 μm) glass, minerals and polymineralic grains, and microfossils downcore with the goal of discerning temporal changes and their underlying causes. Between 214 and 160 mbsf, the dominant coarse particle type changes from rounded, clay-rich granules, interpreted as altered pumice, upward to fresh, angular volcanic glass. This change correlates with an upward increase in turbidite thickness noted by Leg 202 scientists. Major and trace element analyses of individual glass shards show a geochemical signature consistent with a source within the adjacent Andean Southern Volcanic Zone. New calcareous nannofossil biostratigraphy brackets the sediment ages of the upper 288 m of the section to between 12.47 kyr and 275 kyr, which is consistent with published ages for the upper 97 m of the section and estimated maximum ages. Based on our dating of the section, the observed change in dominant coarse sediment type occurs between 225 and 185 kyr and correlates with a climatic transition from interglacial to glacial conditions. A plausible connection with climate is that the altered pumice grains formed by chemical weathering and fluvial transport under warm surface conditions, whereas the glass shards were transported by aeolian and glacial processes, leading to a lack of weathering and an angular texture. However, as a climate-related temporal change, this scenario conflicts with the absence of a similar change in sediment type during the subsequent Valdivian and Llanquihue interglacial-glacial transition starting at about 125kyr. Therefore, our conclusion is that, although the two coarse sediment types formed and were transported under different climate conditions, the temporal change is related to a shift in sediment source, supply or transportation pathway during the 185–225 kyr interval. A related possibility is that the onset of angular glass involvement in turbidity flows, during a glacial stage, marks the eruption of a new volcanic source or sources. Resolving these possibilities could be addressed with more detailed geochemical analysis.
Article
Occasionally, distinctive plant fragment (PF)-concentrated sandstone beds are found in the turbiditic sequence of the Miocene Kawabata Formation (Yubari, central Hokkaido, Japan) deposited in a foredeep basin. Sedimentological and organic geochemical analyses were carried out on the PF-concentrated sandstone bed to investigate the transport and depositional processes of the abundant PFs in the basin. The PF-concentrated sandstone bed was subdivided into lower and upper PF-concentrated layers based on their sedimentary structures. The lower layer contains chaotically dispersed PFs, and the upper layer is characterized by PF laminae. The dispersed PFs in the lower layer were likely deposited by rapid depositional processes such as freezing or rapid fall-out of suspended particles. The huge amount of PF deposition was confirmed by biomarker data such as sterane distributions and pristane/phytane ratios. The compositions of n-alkanes and diterpenoids in the PF-concentrated sandstone bed are distinct from those in the other sandstone and mudstone beds. These results imply that the terrigenous particles originated from specific terrestrial higher plants that were effectively transported and deposited, resulting in formation of the PF-concentrated sandstone bed. The distinctive sedimentary structures observed in the sequences could be attributed to a large flood discharge and the huge volume of PFs might have been transported directly from an upper reach of river and then reached the deep-sea basin by density flows, such as relatively concentrated hyperpycnal flows.
Article
The deep-marine environment is a complex setting in which numerous processes —settling of pelagic and hemipelagic particles in the water column, sediment gravity flows (downslope density currents; turbid flows), and bottom currents— determine sediment deposition, hence a variety of facies including pelagites/hemipelagites, contourites, turbidites and hyperpycnites. Characterization and differentiation among deep-sea facies is a challenge, and numerous features may be highlighted to this end: sedimentary structures, geochemical data, micropaleontological information, etc. Ichnological information has become a valuable, yet in some cases controversial, proxy, being in most of cases understudied. This paper gathers the existing ichnological information regarding the most frequent deep-sea facies —from those in which ichnological analyses are numerous and detailed (e.g. pelagites/hemipelagites and turbidites), to those for which ichnological information is lacking or imprecise (hyperpycnites and contourites). This review analyses palaeoenvironmental (i.e., ecological and depositional) conditions associated with deep-sea sedimentary processes, influence of these changes on the tracemaker community, and associated ichnological properties. A detailed characterization of trace fossil assemblages, ichnofabrics and ichnofacies is presented. Special attention is paid to variations in trace fossil features, approached through sedimentary facies models and the outcrop/core scale. Similarities and differences among deep-sea facies are underlined to facilitate differentiation. Pelagic/hemipelagic sediments are completely bioturbated, showing biodeformational structures and trace fossils, being characterized by composite ichnofabrics. The trace fossil assemblage of muddy pelagites and hemipelagites is mainly assigned to the Zoophycos ichnofacies, and locally to the distal expression of the Cruziana ichnofacies. Turbidites are colonized mostly from the top, determining an uppermost part that is entirely bioturbated, the spotty layer; below it lies the elite layer, characterized by deep-tier trace fossils. Turbidite beds pertain to two different groups of burrows, either “pre-depositional”, mainly graphogliptids, or “post-depositional” traces. Turbidite deposits are mostly characterized by the Nereites ichnofacies, with differentiation of three ichnosubfacies according to the different parts of the turbiditic systems and the associated palaeoenvironmental conditions. There are no major differences in the trace fossil content of the hyperpycnite facies and the classical post-depositional turbidite, nor in the pelagic/hemipelagic sediments, except for a lower ichnodiversity in the hyperpycnites. Trace fossil assemblages of distal hyperpycnites are mainly assigned to the Nereites ichnofacies, while graphogliptids are scarce or absent. Ichnological features vary within contourites, largely related to palaeoenvironmental conditions, depositional setting, and type of contourite. Ichnodiversity and abundance can be high, especially for mud-silty contourites. The ichnological features of mud-silty contourites are similar to those of the pelagic/hemipelagic sediments (the tiering structure probably being more complex in pelagic/hemipelagic) or to the upper part of the muddy turbidites (contourites probably being more continuously bioturbated). No single archetypal ichnofacies would characterize contourites, mainly assigned to the Zoophycos and Cruziana ichnofacies.
Chapter
Deepwater environments tend to collect sedimentary deposits in discrete events in a bed-by-bed fashion, which is markedly different from terrestrial and shallow marine settings that are more commonly affected by persistent reworking of the bed. Deepwater sedimentation units, or beds, contain myriad sedimentary structures and bed fabrics that reflect a wide range of sediment transport and depositional mechanisms, from pelagic to hemipelagic processes, sediment gravity flows, to along slope bottom currents, to upslope drivers such as internal waves and tides. This chapter explains the range of sedimentation units deposited through these different mechanisms, and how these beds and their stacking patterns are used to interpret paleoenvironmental conditions in deep sea and lake environments.
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The main aim of this study is to constrain the range of reservoir properties observed in various depositional environments of the fine-grained sandstones of the early Silurian middle Qusaiba Member, Qalibah Formation, northwestern Saudi Arabia. Facies analysis, micro-X-ray fluorescence (μXRF), lamina-scale permeability measurements, automated helium porosity-permeability measurement, and pore system visualization were integrated to observe variations in these various environments. Seven main facies were recognized and interpreted to be deposited in an offshore “turbiditic-influenced” to lower shoreface paleoenvironments. These facies include current rippled siltstone (F1); Contorted silty sandstone (F2); current rippled fine-grained sandstone (F3); planar-laminated fine-grained sandstone (F4); Bioturbated to current-rippled argillaceous siltstone to silty sandstone (F5); Current rippled silty sandstone (F6); bioturbated sandstone (F7) facies. These facies were clustered into several fabric classes; 1) contorted fabrics associated with load casts flame structure that is characteristic of F2: These typically revealed slightly higher porosity and permeability values than the surrounding media with a spherical and relatively low anisotropy. 2) Planar-laminated fabrics in F4 that overlain by cryptic bioturbation: It comprises of clay mineral-rich laminae with higher porosity and permeability and the quartz-rich laminae with lower porosity and permeability probably due to abundant calcite cement associated with detrital quartz. Higher anisotropy, associated with this fabric, was observed. Cryptic bitourbated interval showed relatively low permeability. 3) In F7, three types of rock fabrics were observed, (1) Vertical sand-filled Piscichnus trace fossil: The burrow fill shows significantly higher porosity and permeability values than the laminated matrix; this fabric reveals an elliptical and highly anisotropic variance map. (2) Horizontal sand-filled Thalassinoides burrow (with iron oxide cement).: The internal core of this fabric was highly porous and permeable compared to the laminated fabric. Thalassinoides fabric had the most elliptical and highest anisotropic variance map in F7. (3) Entirely laminated fabric with bed-parallel gypsum veins: The permeability of the veins was slightly higher than that of the matrix, this resulted in a less anisotropic variance map. μCT scanning was used for F5 and F6; In the F5 facies, more significant porosity associated with quartz-rich lamina than iron oxide (e.g., siderite) and gypsum-rich lamina were observed probably due to higher chlorite alignment in the iron oxide-rich lamina. We found lower porosity and permeability within the vertical mud-filled burrows (Piscichnus) than the laminated fabric; this was also observed in the 3D pore system imaged by μCT scanning. These findings could have significant implications for different fabric types in fluid flow conduits in argillaceous sandstone and siltstone systems.
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We used waterborne Ground Penetrating Radar (GPR) for mapping stratigraphic boundaries, sedimentation environments, and specific features of lacustrine sediments of postglacial Lake Polevskoye, which is located in Eastern Fennoscandia, near Lake Onega. The purpose of our study was to examine the spatial structure of the lacustrine sediments including particular facies represented by the thin interbedding of sand and clay in order to understand the conditions for their formation. The lake bottom morphology and stratigraphic boundaries beneath were mapped with a GPR with 150 MHz antenna unit and then made drill holes to verify GPR interpretations. The GPR measurements, verified by drilling, have vertical accuracy in the range of 0.12–0.36 m. We delineation specific GPR facies in the topmost part of varved clays and classified them as lacustrine turbidites by their structure and grain size. Further studies suggested that turbidites could be deposited by hyperpycnal flows during water discharge from glacial Lake Onega in the period 11.4–10.7 cal ka BP. The architectural implications of the turbidity current in the lake include localized layered sediments 0.5 m thick overlying an erosional surface, which contain unconformable sandy layers and plant debris. A GPR-based 3D model helped us to reconstruct the turbidity current direction, establish its confinement to a lake bottom depression, and consider the associated erosion processes. The near-bottom turbidity current passed through Lake Polevskoye from north to south, along with the bottom depression, and the eastern shore was eroded with a hydraulic jump. The hyperpycnal flows in the study site are associated probably with the last phase deglaciation of the terrain and a drop of the level of Lake Onega because these processes were the most prominent in recent geological history.
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Understanding the flow processes that form gravity flow deposits is vital for modelling and prediction of sandstone bodies in the subsurface, which is of great significance for conventional and unconventional oil and gas exploration and development. This study analyses gravity flow deposits in the Late Triassic Chang 7 member of Yanchang Formation in the Ordos Basin, using a combination of well-log analysis, core observations, thin section analysis, and laboratory measurements. Through this, the sedimentary facies, formational mechanisms, distribution patterns, and depositional models of gravity flow deposits are investigated. Thirteen facies and eight-bed types are recognized in the gravity flow. Bed types represent deposits of sandy slides, sandy slumps, muddy debrites, sandy debrites, hybrid event beds, transitional flow deposits, surge-like low-density turbidites, and quasi-steady-state low-density turbidites. Gravity flow deposits, particularly those caused by sediment failure, are composed of slides, slumps, sandy debrites, hybrid event beds/transitional flow deposits, and surge-like low-density turbidites. These deposits form as lenticular sand bodies, with retrogradational internal stacking patterns. Gravity flow deposits caused by hyperpycnal flow are composed of sandy debrites, hybrid event beds/transitional flow deposits, and quasi-steady-state low-density turbidites. These deposits exhibit elongate morphologies in the southern part of the basin, with progradation internal stacking patterns. The collision between the North China Block and South China Block, which occured during the closing of Qinling Ocean, lead to frequent volcanic eruptions and earthquakes. This likely promoted the development of gravity flow deposits associated with sediment failure from delta fronts in both the northeastern and southwestern parts of the basin. Concurrently, extremely humid climatic conditions promoted increased run-off in the hinterland and heightened fluvial drainage, which ultimately lead to enhanced hyperpycnal flows into the deep-lacustrine basin depocenters. Keywords: Gravity flow deposits, depositional model, deep-lacustrine, Yangchang Formation, Ordos Basin
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The Vaca Muerta Formation is a fine-grained marine stratigraphic unit accumulated during the Late Jurassic-Early Cretaceous in the Neuquén Basin, Argentina. This contribution presents a sedimentological and stratigraphic analysis of Vaca Muerta´s shales emerged from the integration of regional and detailed outcrop research and subsurface data gathered from the study of different well cores. The fieldwork comprised, on the one hand, the description of 7 stratigraphic sections of the Early Tithonian-Early Valanginian interval widely distributed across the western region of the Neuquén province and southern Mendoza province. The sedimentological and sequence-stratigraphic analysis of the different stratigraphic sections allowed integrating them into a regional N-S oriented correlation panel covering an area of 340 km. Five composite depositional sequences were recognized (GS1-GS5). They represent the evolution of a complex mixed shelf/ramp depositional system comprising from basinal/slope facies (central area) to ramp (northern area) and mixed-shelf to continental deposits (southern area). Depositional sequences are represented by thin, organic-rich (up to 10 % TOC), mudstone dominated transgressive cycles, whereas regressive cycles are commonly thicker and mainly composed of organic-lean, carbonate and mixed (carbonate/siliciclastic) facies. On the other hand, aiming at studying the transport and accumulation processes of Vaca Muerta´s organic-rich shales, hand specimen samples of early-diagenetic carbonate concretions were collected from the organic-rich basal condensed section deposited in basinal settings. Concretion samples were thoroughly examined (mm- μm scale) integrating the observation of macroscopic polished samples, thin sections and scanning-electron microscope analyses. The evidence found inside concretions suggest an origin related to muddy underflows, possibly triggered by slope failures on the western margin of the basin. The bedload and suspended-load transport of mud within these muddy underflows would have resulted in the accumulation of graded event mudstone beds exhibiting ripple lamination. Petrographic analysis demonstrates that muddy underflows would have been important mechanisms for reworking the seafloor and redistributing mud in basinal settings. Furthermore, muddy underflows would have been effective processes for organic matter concentration in organic-rich mudstone strata (up to ≈ 6 % TOC). The subsurface studies comprised the sedimentological analysis of seven well cores of the Vaca Muerta Formation, representing a total core data of 387 m. The descriptive facies analysis at centimeter scale allowed the recognition of a distally steepened mixed ramp system. Sediment delivery to basinal settings was mainly controlled by muddy underflows triggered by different mechanisms. Deposition from muddy underflows would have interacted with fallout processes from buoyant plumes and marine snow from the water column. The stacking pattern of the studied core deposits shows ≈ 0.5 to 3 m-thick parasequences building up prograding/retrograding parasequence sets of high-order depositional cycles (10-20 m thick).
Presentation
The divine teacher-student relationship among three generations of Indian geoscientists (1940s-2020s): a remarkable story of knowledge transfer from T. N. Muthuswami Ayer or "TNM" (a crystallographer and mineralogist) through A. Parthasarathy (an engineering geologist and quantitative sedimentologist), to G. Shanmugam (a process sedimentologist and petroleum geologist) and beyond
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Channels are considered effective conduits that deliver terrigenous sediments into related depositional basins, and they are the targets of petroleum exploration and production. Three-dimensional (3D) seismic data, well data, and attribute maps were used to study five types of channels observed in the Shahejie Formation of the Zhanhua Depression, namely erosional channels, confined channels, semi-confined channels, distributary channels, and transitional channels. The channels originated from hyperpycnal flows related to bed load, suspended load, and lofting processes from proximal to distal regions, which were primarily accumulated on medium and low terrains. The hyperpycnal channel systems were primarily identified as three stages with morphological changes in the Es3l and Es3m intervals on a seismic section. Stage 1 was developed during the late period of the Es3l interval, and stages 2 and 3 were developed during the early and middle periods, respectively, of the Es3m interval. Stage 1 is the initial/young stage formed during a phase of low accommodation. Channels of stage 1 are predominantly entrenched with moderately aggregated width and thick channelized splays. Stage 2 is the transitional stage formed during a phase of increasing accommodation. Channels of stage 2 are predominantly meandering with narrowly aggregated width and dispersed frontal splays. Stage 3 is a waned stage, formed during the events of increasing lake levels without comparable increase in sediment flux. This stage involves slight incisions, broad U-shaped morphology channels, and the prevalence of overbank sediments. The depositional architectures, processes, and the development of hyperpycnal channel systems correspond with the lake level and climate conditions of the proposed stages and were controlled by tectonic activity and source supply. Understanding the distribution and development of lacustrine hyperpycnal channels is important to improve and enrich theories of lacustrine sediment gravity flow.
Article
The shallow-marine turbidite fans in the Upper Miocene Huangliu Formation of the Yinggehai Basin in the northwestern South China Sea (SCS) provide an excellent opportunity to understand their sedimentary processes in a shelf depositional environment. The down-slope gravity flow processes and along-slope bottom-current reworking processes of shallow-marine turbidite fans were interpreted by using seismic, well logging, core, petrographic, geochemical, and petrophysical data. Several depositional elements were identified in the shallow-marine turbidite fans, namely, channel-fill high-density turbidites (HDTs), channel-fill low-density turbidites (LDTs) and associated frontal splays, sand-rich/mud-rich lobe deposits, and bottom-current reworked channel-fill/lobe deposits. Deep U-shaped (or V-shaped) seismic reflections and low root-mean-square (RMS) amplitudes characterize the channel-fill HDTs that consist of massive fine-grained sandstones with mud clasts. The channel-fill LDTs, characterized by V-shaped or worm-shaped reflections, mostly consist of normally graded, laminated and rippled, very fine-grained sandstones. Frontal splays are generally associated with channel-fill LDTs. The sand-rich lobe deposits show continuous high-amplitude sheet-like reflections and consist of HDTs and LDTs, whereas the mud-rich lobe deposits show continuous moderate-amplitude reflections and consist of muddy debrites. The bottom-current reworked sandstones (BCRSs), which comprise well-sorted, fine-grained sandstones with traction-current structures, are usually located in the upper parts of thick sandbodies. The variability of depositional elements from large-scale channel-fill HDTs with strong basal erosion in fan-1 to small-scale channel-fill LDTs in fan-2 is closely linked with sea-level fluctuations that result in variable gravity-flow energy and sediment input. However, the reoccurrence of large-scale channel-fill HDTs in fan-3 at sea-level highstands may possibly be attributed to enhanced sediment input from the source areas. Down-slope flow transformation from turbidity flows into muddy debris flows within an individual channel-lobe complex (CLC) resulted in a dramatic increase in clay content and resultant decreasing reservoir quality from the channel-fill HDTs to the mud-rich lobe deposits, because muddy sediments are incorporated into the precursor turbidity flows and turbulence is suppressed. Additionally, it is suggested that the widely developed traction-current structures and tidal signatures (double mud layers, mud-draped ripples, discrete wavy bedding, internal truncation surface, and convex-up laminae) are the products of reworking by internal waves and -tides. During periods of sea-level highstands, the upper parts of gravity-flow sandstones would undergo bottom-current reworking, thus resulting in the retransportation of muddy fines and the formation of reworked sandstones with traction-current structures and tidal signatures. In this study, a combination of traction-current structures, tidal signatures, vertical sequences showing sharp upper contacts and non-gradational upper contacts, and trace elements is considered to be convincing diagnostic criteria in distinguishing reworked sandstones from gravity-flow sandstones. The representative bottom-current reworked sandstones should be preferable hydrocarbon targets in further exploration because of their better reservoir properties compared with gravity-flow sandstones. This research offers some insight into gravity-flow processes and bottom-current reworking processes in a shallow marine environment.
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Detailed facies characterization of the Middle Devonian Geneseo Formation in the Northern Appalachian Basin (NAB) shows a rich assembly of sedimentary features and textures that suggest shelfal mud deposition in a stormdominated, shallow epeiric sea. At the time of deposition, Acadian uplift supplied fine-grained detritus from the east and stimulated delta growth. As sediment was shed from the hinterland, distribution of mudstone facies was controlled by a combination of autogenic processes and a general rise in sea level. The vertical and lateral distribution of nine mudstone facies observed in this succession indicates an overall shallowingupwards trend (westward progradation of Catskill delta) with multiple modes of sediment transport and deposition. The water column became more oxygenated upsection as indicated by an increase in benthic fauna diversity (e.g., Leiorhynchus and Orbiculoidea), increasing bioturbation diversity (e.g., Chondrites, Palaeophycus, Planolites, Teichichnus, Thalassinoides, and Zoophycos), and a decline of organic-carbon content (via oxidation and consumption). Physical and biological attributes of this mudstone-dominated succession are used to reconstruct sedimentary processes and depositional conditions. Although a stratified-basin model has previously been proposed for the Geneseo Formation, observations made in this study do not support that interpretation. Collectively, our observations indicate shelfal mud deposition above storm-wave base, in a relatively energetic environment with persistent lateral transport and advection by oscillatory flow, waveinduced currents, river-flood, and storm-wave generated offshore-directed underflows, as well as storm setup-relaxation flows.
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Integration of basin analysis with arenite petrography provides a powerful tool in obtaining palaeogeographic reconstructions. However, several factors need to be considered if ancient geological settings are to be correctly interpreted. The following concepts are outlined 1. A classification of the main types of grains in arenite frameworks according to temporal (coeval versus non-coeval), spatial (intrabasinal versus extrabasinal) and compositional criteria. 2. A calibrated procedure for detecting coeval versus non-coeval carbonate grains. This technique is applied, and the palaeogeographic implications are illustrated, in a case study: the Paleogene arenites of the Ager valley, Pyrenees. 3. A classification scheme for volcanic grains, involving five classes dependent on palaeovolcanic and neovolcanic sources. A case history, volcanic Quaternary sands deposited in the Nankai Trough off south-western Japan, illustrates the application of the scheme. 4. Compositional and textural criteria which manifest the presence of multicycle as opposed to first-cycle components in the siliciclastic sand framework. The proposed criteria area applied in a case history: modern sands carried by rivers to the Northern Adriatic Sea. 5. The effect of grain size on detrital mode data obtained by optical analyses. A slight modification of the Dickinson point-counting method (1970) as originally proposed by Gazzi (1966) enables loss of information to be avoided and the dependence of composition on grain size to be minimized. 6. Factors which complicate the connection between source area and depositional basin in palaeogeographic reconstructions. Examples are presented for the influence of sea-level variations, littoral drift currents, dominant winds, continental glaciations, cannibalism and tectonic setting.
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This paper illustrates the problems involved in selecting the petrographical classes to be used in quantitative studies of arenites and proposes criteria whereby the dependence of rock composition on grain size is minimized and a satisfactory separation is obtained between arenaceous components which are either coeval with the deposit (mainly intrabasinal) or else significantly older (mainly extrabasinal). -Author
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The origin of massive sands in turbidite successions has commonly been attributed to the rapid dumping of sand due to flow unsteadiness in collapsing, single surge-type, high-density turbidity currents. The general applicability of this model is questioned, and it is proposed that rapid deposition of massive sands also occurrs due to non-uniformity in prolonged, quasi-steady high-density turbidity currents. -from Authors
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An empirical modelling that allows a prediction the amount of atmospheric CO2 consumed by continental erosion is combined with a river-routing file in order to determine the spatial distribution of river carbon inputs to the world's oceans. The total fluvial carbon input is calculated to be 710 teragrams of carbon per year (TgC/yr). 205 TgC/yr are discharged as dissolved organic carbon, 185 TgC/yr as particulate organic carbon, and 320 TgC/yr as bicarbonate ions. Of the latter figure, 230 TgC/yr stem from the atmosphere, while the remainder 90 TgC/yr originate from carbonate mineral dissolution. The Atlantic Ocean receives the greatest amount of river carbon, followed by the Pacific Ocean, the Indian Ocean, and the Arctic Ocean. The spatial distribution of the predicted river carbon inputs may be included in further modelling studies in order to better understand the lateral transports of carbon in the present-day global carbon cycle.
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Facies and facies associations of ancient flood-dominated depositional systems include a very broad spectrum of essentially poorly described and understood sediments that vary from thick-bedded and disorganized conglomerates to thin-bedded graded mudstones via a great variety of pebbly-sandstone and sandstone facies. Despite this variability, all these sediments are characteristically composed of graded flood units in both alluvial and marine environments. The greatest preservation potential of individual flood units is found in the final marine depositional zones of each system considered. Ancient flood-dominated fluvio-marine systems comprise huge accumulations of conglomerates, sandstone and mudstone facies whose origin and stratigraphic importance have been essentially overlooked in previous literature. These depositional systems can be understood only in terms of tectonically-controlled physiographic settings characterized by small and medium-sized fluvial systems with high-elevation drainage basins and high-gradient transfer zones located close to marine basins. In settings of this type, sediment flux to the sea can dramatically increase when climatic conditions provide sufficient amounts of water to produce catastrophic floods. These floods generate mixtures of water and sediment that can enter sea waters with sufficient velocity and sediment concentration to produce hyperpycnal flows and related, self-sustained turbidity currents. The resulting depositional settings are thus dominated by flood-related facies that can develop in shelfal or deeper marine regions. Thick and laterally extensive successions of shelfal sandstone lobes with flood-generated HCS are the fundamental depositional element of both fan-delta and river-delta systems considered in this study. These lobes are essentially similar to deeper-water turbidite sandstone lobes in terms of geometry, facies tracts, and high-frequency cyclic stacking patterns. Shelfal sandstone lobes probably represent the only possible expression of fluvial-dominated delta-front sandstone facies, since, in the absence of flood-generated hyperpycnal flows, river-borne sands can only be redistributed in marine environments by waves and tides. As indicated by their overall stacking patterns, the evolution of ancient flood-dominated fluvio-deltaic systems with time is apparently controlled by the initial uplift of the drainage basin, the rate of denudation, the gradient of each system, and the volume and sediment concentration of individual floods, the latter being a function of the amount of water and sediment made available to the system considered. A flood-dominated system of this type comes to an end when the sediment flux to the sea is progressively reduced to "normal" conditions. This occurs when relief and elevation of drainage basins and related sediment availability, as well as the gradient of transfer zones, have been substantially reduced through progressive denudation and sediment exportation to marine depositional zones. The occurrence of cyclic stacking patterns developed at different hierarchical orders is one of the most striking aspects of flood-dominated fluvio-deltaic systems. The most complete record of this cyclicity is preserved in the final depositional zone of each system. These stacking patterns are apparently very similar to those which are thought to be characteristic of sequence-stratigraphic models. Despite this apparent similarity, we suggest that the overall vertical evolution of flood-dominated systems is primarily controlled by Davisian-type cycles produced by alternating periods of orogenic uplift and denudation. In their most complete development, these cycles are ideally recorded by an overall forestepping-backstepping succession recorded by a basal turbidite system (basin floor fan of sequence stratigraphy) overlain by a flood-dominated fluvio-deltaic system which passes upward and landward into a "normal" fluvial or fluvio-deltaic system with time. Higher-frequency stacking patterns developed within each of the above stages are essentially produced by forestepping-backstepping episodes of sand deposition which are essentially controlled by cyclic climatic variations. The relationships between Davisian-type and higher-frequency climatic cycles and eustasy-driven cycles of relative sealevel variations remain to be explored through careful stratigraphic, sedimentological and structural studies carried out without preconceived ideas. 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