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(A) Schematic diagram showing common types of gravity-driven downslope processes (slides, slumps, debris flows, and turbidity currents) that transport sediment into deep-marine environments (modified from Shanmugam et al., 1994). (B) Sediment concentration (percentage by volume) in gravity-driven processes derived from several published sources. Note that turbidity currents are low in sediment concentration (i.e., low-density flows) (modified from Shanmugam, 2000). (C) Based on mechanical behavior of gravity-driven downslope processes, mass-transport processes are considered to include slide, slump, and debris flow but not turbidity current (Dott, 1963). (D) The prefix sandy is used for mass-transport deposits (SMTD) that have grain (>0.06 mm; sand and gravel) concentration values equal to or above 20% by volume. The 20% value is adopted from the original field classification of sedimentary rocks by Krynine (1948). See Shanmugam (2012b).
Contexts in source publication
Context 1
... sliding motion of failed soil mass com- mences along the shear surface when the factor of safety (F) is less than 1 ( Figure 1B). Once the sliding motion is initiated on continental margins, other gravity-driven downslope processes such as slumps, debris flows, and turbidity currents ensue (Figure 2). Dott (1963) proposed the most mean- ingful and practical classification of subaqueous gravity-driven processes into mass-transport pro- cesses and turbidity currents. ...
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... (1963) proposed the most mean- ingful and practical classification of subaqueous gravity-driven processes into mass-transport pro- cesses and turbidity currents. The importance of Dott's classification is that mass-transport processes do not include turbidity currents (Figure 2). Despite the well-established basic types of gravity-driven processes, Dunham and Saller have selectively em- phasized turbidity currents. ...
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... the Kutei Basin examples, the boundary that separates each Bouma division is unconvincing. In figure 2 of Dunham and Saller (2014;reproduced from Saller et al., 2006, their figure 10), for ex- ample, the boundary between Ta and Tb divisions is an imposed one. By definition (Bouma, 1962), the Ta is a single discrete division within the Bouma sequence. ...
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... definition (Bouma, 1962), the Ta is a single discrete division within the Bouma sequence. However, Dunham and Saller (2014, their figure 2) have included two distinct divi- sions (an upper light-colored division and a lower dark-colored division) within the Ta. The bottom shale unit shows parallel lamination, which is simi- lar to overlying Ta and Tb divisions. ...
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... one would interpret the origin of each sandy layer with parallel lamination by bed-load traction and the origin of each coaly layer (mud) by settling from suspension. In other words, the cored interval in Figure 2 is composed of multiple depositional events. Ironically, Dunham and Saller, in my opin- ion, misinterpreted multiple depositional events in their figure 2 as a single event, which defies the original concept of Bouma. ...
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... Lenticular bedding. Their figure 10 (see Dunham and Saller, 2014, their figure 2) shows several examples of lenticular bedding at the bottom part of the photograph, next to the scale bar (i.e., the interval between the middle arrow and the bottom of the photograph). ...
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... the Krishna-Godavari Basin core, although one could designate the DML in- tervals (Figure 3) as Tb and the massive sand unit (Figure 3, between scale divisions 2 and 4 cm [0.8 and 1.6 in.]) as Ta, I did not. A striking similarity is observed between the Krishna-Godavari Basin core (Figure 3) and the Kutei Basin cores (see Saller et al., 2006, their figures 10 and 11; Saller et al., 2008a, their figure 17; Dunham and Saller, 2014, their figure 2; in particular, Tb divisions). I suggest that DML in the Kutei cores indicate deposition by deep-marine tidal currents. ...
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... currents associated with various mod- ern oceanographic phenomena in the Makassar Strait are (1) documented Indonesian through- flow ( Gordon, 2005), (2) observed internal waves (Hatayama, 2004), (3) observed internal tides ( Ray et al., 2005), and (4) measured velocities of deep tidal currents ( Nummedal and Teas, 2001;Wajsowicz et al., 2003). Because Saller et al. (2006) have failed to consider alternative bottom-current origins for Miocene sands in the Kutei Basin, I wrote a critique (Shanmugam, 2008a) of their article. In acknowledging the existence of modern bottom- current processes, Dunham and Saller (2014, p. 852) state that, "we agree that all of these phenomena have been documented in the Makassar Strait. ...
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... The active sedimentary activities in the BBL are directly related to the ocean dynamical processes at multiple scales. Observations have shown that various physical processes, such as tides (Stow et al., 2002;He et al., 2008;Zhao et al., 2019), seasonal current reversals (DeMadron and Weatherly, 1994;Gao et al., 1998), mesoscale eddies (Zhang et al., 2014), internal waves (Hosegood and Van Haren, 2004;Pomar et al., 2012;Shanmugam, 2013;Shanmugam, 2014), and deep-sea storms (Hollister et al., 1974;Nowell and Hollister, 1985;Hollister, 1993) can affect sedimentation in the BBL. The energy and momentum carried by those oceanic dynamical processes can be strongly dissipated in the BBL (McWilliams, 2005), leading to an increase in current velocity and shear stress , causing resuspension (Quaresma et al., 2007;Schaeffer et al., 2013;Sun et al., 2016) and even intermittent movement of sediments on the seafloor (Butman et al., 1979). ...
Ocean dynamic processes in the bottom boundary layer (BBL) are crucial for sedimentation, such as deposition and resuspension of marine sediments. In this study, we conducted in-situ tripod observations of the sediment ridge of a contourite drift in the northern South China Sea to understand the main dynamic processes affecting sedimentation on the contourite drifts. It was found that the diurnal tidal current was the strongest current at the study site, thus acting as the main dynamic affecting sedimentation processes. Periodic events of elevated suspended sediment concentration (SSC) were observed, some of which occurred only within 15 m above the seafloor and were termed near-bottom high SSC events, while others covered the entire range of the observed water column and were termed full-depth high SSC events. In-situ sediment resuspension at the sediment ridge is not an important factor affecting the formation of high SSC events. Rather, these high SSC events were mainly caused by lateral transport of sediments from the main body of the contourite drift by the northwestward diurnal tidal currents. The seafloor sediments at the main drift body are resuspened owing to the near-critical reflection of diurnal tidal currents on the slope topography of the drift. During periods when diurnal tidal currents were weak, locally generated internal waves could also induce burst-like full-depth high SSC events. This study highlights the diurnal tidal current as the main dynamic regulating the sedimentary processes of the contourite drifts in regions where the near-critical reflection prone to occur, implying the complexity of sediment dynamics of contourite drifts.
... Some authors suggest that the moat formation, or contourite formation in general, could be also influenced by internal waves or turbulence at the density contrast between two water masses 4,20,22,27,[42][43][44] . Others suggest that they form in association with ocean current surface fronts 27,45 . ...
Ocean currents control seafloor morphology and the transport of sediments, organic carbon, nutrients, and pollutants in deep-water environments. A better connection between sedimentary deposits formed by bottom currents (contourites) and hydrodynamics is necessary to improve reconstructions of paleocurrent and sediment transport pathways. Here we use physical modeling in a three-dimensional flume tank to analyse the morphology and hydrodynamics of a self-emerging contourite system. The sedimentary features that developed on a flat surface parallel to a slope are an elongated depression (moat) and an associated sediment accumulation (drift). The moat-drift system can only form in the presence of a secondary flow near the seafloor that transports sediment from the slope toward the drift. The secondary flow increases with higher speeds and steeper slopes, leading to steeper adjacent drifts. This study shows how bottom currents shape the morphology of the moat-drift system and highlights their potential to estimate paleo-ocean current strength.
... A large Contourite Depositional System (CDS) has been recognised along the northern Argentine and Uruguayan margin 2016b;Preu et al., 2012;2013). The CDS includes three large contourite terraces that have been documented along the continental margin off the Río de la Plata Estuary (northern Argentina) in close proximity to the Mar del Plata (MdP) submarine Canyon (Preu et al., 2012. ...
... The Ewing Terrace is associated with plastered drifts at the basinward side, but at the La Plata Terrace no plastered drifts could be recognised Preu et al., 2013). Two channels where found in the landward side of the Ewing Terrace that were recently reclassified as moats due to the evidence of sedimentation and its association with a separated mounded drift ( Fig. 3.2; Bozzano et al., 2011;Preu et al., 2012;2013;Voigt et al., 2013;Steinmann et al., 2020). Steinmann et al. (2020) described the southern moat for the purpose of analysing cold-water corals in close proximity to this moat. ...
... CMP bin size varies among profiles between 5 and 10 m depending on data quality and coverage. After the CMP stacking a residual static correction and finite-difference time migration was calculated (Preu et al., 2012;2013). For interpretation of the data, the software package 'The Kingdom Software' (IHS Markit) was used. ...
Oceanic currents flowing near the seafloor erode, transport and deposit sediments, organic carbon, nutrients, and pollutants in deep-water sedimentary systems. Sediment deposits, which have mainly formed under the influence of these bottom currents (contourites) are high-resolution archives for reconstructing past ocean conditions. However, the interaction of sedimentary systems with oceanographic processes in deep-water environments is not well understood. The main objective of this thesis is to better understand the connection between contourites and the hydrodynamics that generate them in order to improve reconstructions of paleocurrents and sediment transport pathways. To achieve this objective a multidisciplinary study combining multibeam bathymetry, seismo-acoustic data, sediment samples, vessel-mounted Acoustic Doppler Current Profiler data, numerical modelling of ocean currents and three-dimensional flume tank experiments has been conducted.
Elongated depressions (moats) and their associated drifts form at the northern Argentine margin on top of relatively flat seafloor surfaces (terraces) next to a steep slope. The main current direction is along-slope, and the speed is higher near the slope and decreases on the terrace basinwards. Flume tank experiments show that a moat-drift system forms if there is a secondary basinward flow near the seafloor. The secondary flow increases with higher speeds and steeper slopes, leading to steeper adjacent drifts. Once the moatdrift system has developed, the secondary circulation is confined by the drift into a helix structure. Simultaneously, the primary along-slope velocity is increased. The measured current speed over the moats from the Argentine continental margin and the Bahamas area is high (up to 63 cm/s at 150–200 m) and decreases by 5-48% over the associated drift. Measurements from 185 cross-sections of moat-drift systems distributed at 39 different locations worldwide show that moats at steeper slopes have a steeper drift and that the angle of the slope side is on average 1.6 times higher than the angle of the drift side.
However, no statistical relation is found between latitude and moat-drift morphology or stratigraphy. The flume tank experiments show that moat-drift systems can form solely because of along-slope currents without any additional oceanographic processes as eddies, internal waves or ocean current surface fronts. However, Acoustic Doppler Current Profiler data and the hydrodynamic model from the Argentine continental margin show that eddies near the seafloor can form on a contourite terrace. These eddies might lead to the small erosion surfaces on the Ewing Terrace, even though it is mainly a depositional environment and currents are relatively weak (below 30 cm/s). Experiments show that the migration of the moat-drift system and the formation of internal stratigraphic architecture is a function of current strength in combination with sediment supply. The different stratigraphic types of more erosive and more depositional moat-drift systems have been observed in seismic data. A new sub-classification of moat-drift systems based on their stratigraphy is proposed.
In summary, this study provides new insights into the interaction between ocean currents and sedimentary systems. It shows the importance of current strength, current variability (in time and space) and sediment supply for the formation of contourite systems. The combined data suggest that higher speeds and steeper slopes intensify the secondary flow, leading to steeper adjacent drifts. Thus, the morphology and internal architecture of the moat-drift systems can be used as a paleo-velocimeter. Furthermore, this study identifies the need for more in situ measurements near the seafloor.
... Sometimes, when delta prograde, mouth bar deposits are incised by the overlying distributary channels (Schomacker et al., 2010). Convoluted bedding, on the other hand, represents sheet sand interbedded with mudstone and siltstone that is distributed in the outer delta front, has a generally serrated shape on the GR log (Fig. 6), and is formed in soft sediments as a result of tsunami, seismic activity, and storms (Luo et al., 2015;Ming-zhen, 2012;Shanmugam, 2013). While interdistributary channels contain mudstone and siltstones and develop in between belt distributary channels in the middle sub-members are considered structureless, and contain a high GR value (Fig. 6). ...
The middle sub-member of the Eocene Shahejie Formation is mainly associated with deltaic environment, and considered as hydrocarbon bearing zone in the southeast of the Bonan Sag, Bohai Bay Basin, China. Previous research and the exploration work in an area were carried out separately, and inconsistency in understanding of stratigraphic division, correlation, and facies was encountered. Furthermore, the facies evolution in the targeted formation is still questionable. To fill these short-comings, sequence stratigraphic correlation and interpretation were conducted on the middle sub-member (Es3z) of the third member (Es3) of Eocene Shahejie Formation in the study area. Integrative facies and paleo-environment analyses are carried out through the correlation study of wireline logs, seismic data and core sedimentology. The sedimentological interpretation reveals that sandstone groups in the Es3z show five different facies associations in both lateral and vertical successions developed in the inner and outer delta front. These depositional facies include deposits in distributary channels, interdistributary channels, mouth bars, natural levees, and sheet sandstones. The Es3z sandstone intervals are characterized by five depositional sequences in terms of the third-order sequence, including Es3z2+3, Es3z4, Es3z5, Es3z6+7, and Es3z8. They are found in all wells consisting of the lowstand, transgressive, and highstand system tracts. These system tracts are separated by the maximum flooding surfaces and correlation boundaries of sandstone groups with unique characteristics of well log motifs, calibrated with the cores by particular lithology. Facies and reservoir heterogeneities are defined within a sequence stratigraphic framework approach for hydrocarbon reservoir prediction. Our results show that sediments were sourced from the southeast toward the northwest. Due to tectonic activity and lake level's fluctuations, reservoir facies are prograding towards the basin side. The steepness of the region impacts the facies and reservoirs evolution together with tectonics and fluctuations in lake level, which turns from the sandy conglomeratic reservoirs into a thick succession of sandstone reservoirs towards the basin side in LST HST and TST system tracts. These reservoir facies are considered as good, and capped by grayish mudstone (inner delta front) to dark gray mudstone (outer delta front) in TST system tracts. The facies architecture of all sandstone groups possesses the hydrocarbons potential in the inner and outer delta front region in which interpreted oil, oil-water layer and water-oil layers show variation in progradation and retrogradation stacking pattern. Among them lower sandstone units of Es3z8 and Es3z6+7 show dominancy in oil rich reservoirs, followed by Es3z2+3, Es3z4 and Es3z5 in LST, HST and TST system tracts. These hydrocarbon units can be correlated laterally with exploration wells for getting new well sites in third order sequence stratigraphic framework. Our findings shed new light on the facies and reservoir heterogeneities, which provide a useful aid for hydrocarbon exploration in the study area.
Key words
Bohai bay basin,Sequence stratigraphic correlation,Well logs, Seismic, Hydrocarbon potential, Reservoir-facies heterogeneities
... Importantly, I debunked the myths of facies models on high-density turbidites (Shanmugam, 1996), questioned the validity of the Bouma Sequence (Shanmugam, 1997(Shanmugam, , 2002, emphasized bottom currents (Shanmugam, 2003(Shanmugam, , 2008(Shanmugam, , 2013Shanmugam et al., 1993Shanmugam et al., , 2009), documented problems with the sequencestratigraphic concept of basin-floor fans , reinterpreted the Ouachita flysch (Shanmugam and Moiola, 1995), argued the concepts of (1) tsunamites (Shanmugam, 2006a, b), (2) seismites (Shanmugam, 2016c), (3) contourites (Shanmugam, 2016b(Shanmugam, , 2017b, (4) hyperpycnites (Shanmugam, 2018a, b), and (5) hybridites (Shanmugam, 2021b). ...
... This list does not represent total contribution by each author. Modified after Allen (1985); Apel (2002); Bagnold (1962); Bouma (1962); Bouma et al. (1985); Briggs and Cline (1967); Curray and Moore (1974); Damuth et al. (1988); Dill et al. (1975); Dott (1963); Dzulynski et al. (1959); Strzebo nski (2022); Embley (1980); Ewing et al. (1971); Forel (1885); Shanmugam (2013); Gill (1982); Gordon (2013); Hampton (1972); Haughton et al. (2009); Shanmugam (2012c); He et al. (2011); Heezen et al. (1966); de Castro et al. (2020); Hern andez- Molina et al. (2013); Hollister (1967); Hsü (1989); Klein (1975); Kuenen (1957); Lonsdale et al. (1972); Lowe (1975); Lowe (1976a); Lowe (1976b); Lowe (1982); Lowe and Guy (2000); Marr et al. (2001); Middleton (1966); Middleton (1973); Middleton and Hampton (1973); Shanmugam and Moiola (1995); Mulder et al. (2003); Murray and Renard (1891); Mutti (1992); Natland (1967); Nelson et al. (1992); Nilsen et al. (1979); Normark et al. (1997); Pequegnat (1972); Pickering et al. (1989Pickering et al. ( , 1995; Pickering and Hiscott (2015); Piper (1975); Piper (1978); Piper and Brisco (1975); Piper and Aksu (1987); Piper et al. (1988); Piper et al. (1997); Piper et al. (2012); Shanmugam (1996); Postma et al. (1988); Viana and Rebesco (2007); Rebesco and Camerlenghi (2008); Sanders (1965); Shanmugam and Benedict (1978); Shanmugam and Walker (1978); Shanmugam and Walker (1980); Shanmugam and Lash (1982); Shanmugam and Benedict (1983); Shanmugam (1985); Shanmugam (1986); Shanmugam (1988); ; ; ; ; Shanmugam and McPherson (1987); Shanmugam et al. (1988a, b); Shanmugam et al. (1988c); Shanmugam (1996); Shanmugam (1997); Shanmugam (2002a); Shanmugam (2003); Shanmugam (2006a); Shanmugam (2006b); ; Shanmugam (2008a); Shanmugam (2008c); Shanmugam (2012a); Shanmugam (2012b); Shanmugam (2013); Shanmugam (2016a); Shanmugam (2016b); Shanmugam (2016c); Shanmugam (2017a); Shanmugam (2018a); Shanmugam (2018b); Shanmugam (2018c); Shanmugam (2019); Shanmugam (2020); Shanmugam (2021a); Shanmugam (2021b); Shanmugam (2021c); Shanmugam (2022a); Shanmugam (2022b); Shanmugam (2022d); Shepard et al. (1979); Southard and Stanley (1976); Stanley and Kelling, 1978;Stanley (1980); Stanley (1981); Stanley (1993); Stanley and Moore (1983); Stanley et al. (1978); Shanmugam (2016a); Stow and Piper (1984); Stow and Fauge'res (1998); Stow et al. (2002); Stow and Faug eres (2008); Walker (1992); Wüst (1933); Zenk (2008). These pioneers and their works are amid 50 notable contributors in the world (Table 1). ...
... This list does not represent total contribution by each author. Modified after Allen (1985); Apel (2002); Bagnold (1962); Bouma (1962); Bouma et al. (1985); Briggs and Cline (1967); Curray and Moore (1974); Damuth et al. (1988); Dill et al. (1975); Dott (1963); Dzulynski et al. (1959); Strzebo nski (2022); Embley (1980); Ewing et al. (1971); Forel (1885); Shanmugam (2013); Gill (1982); Gordon (2013); Hampton (1972); Haughton et al. (2009); Shanmugam (2012c); He et al. (2011); Heezen et al. (1966); de Castro et al. (2020); Hern andez- Molina et al. (2013); Hollister (1967); Hsü (1989); Klein (1975); Kuenen (1957); Lonsdale et al. (1972); Lowe (1975); Lowe (1976a); Lowe (1976b); Lowe (1982); Lowe and Guy (2000); Marr et al. (2001); Middleton (1966); Middleton (1973); Middleton and Hampton (1973); Shanmugam and Moiola (1995); Mulder et al. (2003); Murray and Renard (1891); Mutti (1992); Natland (1967); Nelson et al. (1992); Nilsen et al. (1979); Normark et al. (1997); Pequegnat (1972); Pickering et al. (1989Pickering et al. ( , 1995; Pickering and Hiscott (2015); Piper (1975); Piper (1978); Piper and Brisco (1975); Piper and Aksu (1987); Piper et al. (1988); Piper et al. (1997); Piper et al. (2012); Shanmugam (1996); Postma et al. (1988); Viana and Rebesco (2007); Rebesco and Camerlenghi (2008); Sanders (1965); Shanmugam and Benedict (1978); Shanmugam and Walker (1978); Shanmugam and Walker (1980); Shanmugam and Lash (1982); Shanmugam and Benedict (1983); Shanmugam (1985); Shanmugam (1986); Shanmugam (1988); ; ; ; ; Shanmugam and McPherson (1987); Shanmugam et al. (1988a, b); Shanmugam et al. (1988c); Shanmugam (1996); Shanmugam (1997); Shanmugam (2002a); Shanmugam (2003); Shanmugam (2006a); Shanmugam (2006b); ; Shanmugam (2008a); Shanmugam (2008c); Shanmugam (2012a); Shanmugam (2012b); Shanmugam (2013); Shanmugam (2016a); Shanmugam (2016b); Shanmugam (2016c); Shanmugam (2017a); Shanmugam (2018a); Shanmugam (2018b); Shanmugam (2018c); Shanmugam (2019); Shanmugam (2020); Shanmugam (2021a); Shanmugam (2021b); Shanmugam (2021c); Shanmugam (2022a); Shanmugam (2022b); Shanmugam (2022d); Shepard et al. (1979); Southard and Stanley (1976); Stanley and Kelling, 1978;Stanley (1980); Stanley (1981); Stanley (1993); Stanley and Moore (1983); Stanley et al. (1978); Shanmugam (2016a); Stow and Piper (1984); Stow and Fauge'res (1998); Stow et al. (2002); Stow and Faug eres (2008); Walker (1992); Wüst (1933); Zenk (2008). These pioneers and their works are amid 50 notable contributors in the world (Table 1). ...
... Occurrence Apel (2002), Apel et al. (2006), and Jackson (2004) have published comprehensive accounts of internal waves and tides worldwide. A sedimentlogic and oceanographic review was provided by Shanmugam (2013). Internal waves are gravity waves that oscillate along oceanic pycnoclines. ...
... Terraced slopes also frequently appear along active margins (Dickinson, 1995) and can be identified in offshore areas around Cyprus associated to plastered drifts along the slope (Tartus Basin) ( Fig. S1 and S2 in supplementary material). Water masses and their secondary oceanographic processes are known to influence flatter domains by extensive development of sandier bottom current deposits, including ripples and small dunes, as documented in both modern and ancient marine records (Mutti et al., 2014;Shanmugam, 2014;Hernández-Molina et al., 2017a;Miramontes et al., 2019Miramontes et al., , 2020Miramontes et al., , 2021de Castro et al., 2021b) and even Mesozoic outcrops (Bádenas et al., 2012;Val et al., 2018). ...
... Phases of flow acceleration caused the recurrence of bed-load traction, with ripples and dune formation; and phases of flow deceleration caused deposition of suspended sediment, which effectively suppressed traction and induced draped lamination and grading. Controlling mechanisms for short-term fluctuations in flow strength remain unknown, although centennial fluctuations (Martorelli et al., 2021) and deep tides (Shanmugam, 2006(Shanmugam, , 2014Rebesco et al., 2014; have been suggested. In summary, the Cyprus contourites record bottom currents that were neither permanent nor semipermanent. ...
... Detailed sedimentologic analysis has provided some criteria for discriminating facies-scale bottom current deposits from turbidites or other deepwater pelagic deposits. Specific contourite sedimentary facies have been described by a number of studies (e.g., Stow and Lovell, 1979;Stow, 1982;Stow and Holbrook, 1984;Stow and Piper, 1984;Pickering et al., 1989;Faugères and Stow, 1993;Gao et al., 1998;Faugères et al., 1999;Stow et al., 2002aStow et al., , 2013aStow et al., , 2013bRebesco, 2005;Llave et al., 2006;Øvrebø et al., 2006;Shanmugam, 2006Shanmugam, , 2012Shanmugam, 2014;Stow and Faugères, 2008;Stow et al., 2013aStow et al., , 2013bRebesco et al., 2014;de Castro et al., 2020de Castro et al., , 2021ade Castro et al., , 2021bStow and Smillie, 2020;Hüneke et al., 2021;Rodrigues et al., 2022a). Recent research proposes new diagnostic criteria for contouritic sedimentary facies (Alonso et al., 2016;Brackenridge et al., 2018;Rodríguez-Tovar and Hernández-Molina, 2018;de Castro et al., 2020de Castro et al., , 2021ade Castro et al., , 2021bStow and Smillie, 2020;Yu et al., 2020;Hüneke et al., 2021;Rodríguez-Tovar, 2022) based on statistical analyses (as Principal Component Analysis, PCA) of texture, microfacies, ichnological features and geochemical data (X-ray fluorescence, XRF). ...
Bottom current deposits (contourites) form in association with modern-day or ancient oceanic gateways. A paucity of examples in the ancient record and the lack of consensus on diagnostic criteria for differentiating them from other deepwater deposits limit our understanding of how they may record past global oceanic circulation, tectonic events and gateway evolution. This work describes an exceptional example of Eocene to middle Miocene deep-marine deposits located both onshore and offshore deepwater environments around the island of Cyprus. Multidisciplinary approaches were used to discriminate contourite facies associations, propose a sedimentary model, and interpret the relations with regional tectonics and the evolution of the nearby Indian Gateway. Contourite deposits appear in late Eocene to middle Miocene intervals interstratified with pelagic/hemipelagic sediments, turbidites and mass-transport deposits (MTDs). These deepwater deposits developed along a slope basin located on the upper plate of an active margin, evolving from a wide basin formed during a period of tectonic quiescent into a series of shallowing-upward, segmented sub-basins affected by compressional stress. The present study proposes a sedimentary model in which two contourite depositional systems developed: first in the Eocene (dominated by finer-grained contourites), and then during the latest Oligocene to middle Miocene (dominated by coarser-grained contourites). Both systems were buried by extensive marl deposits and record the respective influence of deep (circulating NW) and intermediate (circulating SE) water masses. The long-term evolution of the contourites reflects tectonic events that enhanced subduction processes south of Cyprus as well as exchange between the Neotethys Ocean and the Indian and Atlantic Oceans —until the final closure of the Indian Gateway by the end of the middle Miocene, when a new circulation pattern was established with the formation of the Mediterranean Sea.
The contourites described here represent bi-gradational sequences that normally form in association with contouritic drifts, sometimes having the asymmetric top-cut sequence characteristics of plastered drifts and contourite terraces. The coarser (sandy) contourites, formed from the latest Oligocene to middle Miocene, consist of three packages associated with compressive and flexural phases. They pertain to I) Chattian (late Oligocene); II) Aquitanian/Burdigalian (early Miocene) and III) Langhian (middle Miocene). Evidence of enhanced bottom current episodes occurs toward the top of these packages before they are buried by later dominant marl deposits. The sandy contourites thus formed during the compressive phases, whereas the predominately finer-grained units formed during later flexural phases. The intermittent turbidites and MTDs (developed during compressional phases in combination with pelagic/hemipelagic sediments) represent the sediment supply for the contourite deposits after their winnowing and / or reworking. Our research found that the diagnostic criteria for discriminating ancient bottom current deposits from other deepwater deposits are related primarily to variations in sedimentary processes, current behaviour and its velocity, sedimentation rates and paleoenvironmental conditions. This highlights the importance of primary sedimentary structures, microfacies and ichnological features in making determinations at the sedimentary facies scale. Due to their common occurrence, sedimentary thickness (30-40 m), potential porosity and permeability, sandy contourites can form deepwater reservoirs for energy geosciences.
In summary, this work demonstrates the role of plate tectonics and oceanic gateways in driving the paleo-oceanic circulation that, in turn, controls sedimentary processes and shapes the morphology of oceanic basins and continental margins. It also allows for comparison with other present-day and ancient continental margin deposits. Future high-resolution approaches and analyses of other geological settings could help resolve the sedimentary architectures of similar deepwater systems in terms of episodic tectonic processes —involving compressive-flexural stress variations. They control the Earth’s surface environment (sea-level, climate and oceanic circulation) over time by influencing sediment supply, packages of strata and types of contourite deposits.
... These include tides, wind-driven currents and surface waves. In general, these flows are driven by pressure gradients caused by a sloping sea surface (Shanmugam, 2013). Baroclinic flows are currents whose surfaces of constant pressure and constant density do not strike parallel to each other and which propagate on density surfaces known as pycnoclines in stratified waters. ...
... The secondary processes of benthic storms, overflows, interfaces between water masses, vertical eddies, horizontal vortices, tides and internal tides, internal waves and solitons, tsunami-related traction currents and rogue or cyclonic waves all influence water-mass circulation (Shanmugam, 2006(Shanmugam, , 2013(Shanmugam, , 2021Rebesco et al., 2014;Hernández-Molina et al., 2016c;Yin et al., 2019). Some of these processes are not well understood and their influence on deepwater sedimentation dynamics and seafloor morphology remains uncertain (e.g., Maier et al., 2019;Miramontes et al., 2019). ...
... Some of these processes are not well understood and their influence on deepwater sedimentation dynamics and seafloor morphology remains uncertain (e.g., Maier et al., 2019;Miramontes et al., 2019). Shanmugam (2006Shanmugam ( , 2013Shanmugam ( , 2017Shanmugam ( , 2021, Rebesco et al. (2014) and Hernández-Molina et al. (2016c) describe general aspects of how secondary processes influence deep-marine sedimentation. Specific details about these processes can also be found in reports on benthic storms (Hollister, 1993;Gardner et al., 2017;Miguez-Salas et al., 2020), overflows (Legg et al., 2009;Glazkova et al., 2021;Yin et al., 2021) (Hollister and McCave, 1984;Liu et al., 2017;López-Quirós et al., 2020), horizontal vortices (Preu et al., 2013;Miramontes et al., 2019), deep tides and internal tides, and internal waves and solitons (Apel, 2000(Apel, , 2004Jackson, 2004;Butman et al., 2006a;Shanmugam, 2006Shanmugam, , 2012Shanmugam, , 2014Miramontes et al., 2020a). ...
Along-slope bottom currents and a series of secondary oceanographic processes interact at different scales to form sedimentary deposits referred to as contourite and mixed (turbidite-contourite) depositional systems. The recent proliferation of both academic and industry research on deep-marine sedimentation documents significant advances in the understanding of these systems, but most nonspecialists remain unaware of the features in question and how they form. Contourites and mixed depositional systems represent a major domain of continental margin and adjacent abyssal plain sedimentation in many of the world’s oceans. They also appear in Paleozoic, Mesozoic and Cenozoic stratigraphic sections. The growing interest in these systems has led to a refined but still evolving understanding of them. In addition to resolving their exact origins and evolutionary trajectories, research must also continue to ascertain their role in deep-sea ecosystems, geological hazards, environmental policy and economic development. Key gaps in understanding persist regarding their formation, their function in oceanographic systems and their evolution over time. This chapter summarizes current conceptual paradigms for contourite and mixed depositional systems, lists global geographic examples of these systems and discusses their identification and interpretation in terms of diagnostic features as they appear in 2D and 3D seismic datasets and at sedimentary facies scale. This chapter also considers the role that bottom currents play in shaping the seafloor and controlling the sedimentary stacking patterns of deepwater sedimentary successions. The growing interest in, and implications of, contourite and mixed depositional systems demonstrates that these systems represent significant deep-marine sedimentary environments. Combined efforts of researchers, industry partners and policy-makers can help advance understanding and responsible stewardship of deepwater depositional systems.
... Muddy tidalites are poor reservoirs (Shanmugam et al., 2009). 14 (6) In the world's oceans, documentation of internal waves and tides is ubiquitous (Lonsdale et al., 1972;Apel, 2002;Shanmugam, 2013). However, recognition of ancient deep-water deposits of internal waves and tides is in the sedimentary record is rare (Gao et al., 1998;He et al., 2011;Pomar et al., 2012). ...
... Muddy tidalites are poor reservoirs (Shanmugam et al., 2009). 14 (6) In the world's oceans, documentation of internal waves and tides is ubiquitous (Lonsdale et al., 1972;Apel, 2002;Shanmugam, 2013). However, recognition of ancient deep-water deposits of internal waves and tides is in the sedimentary record is rare (Gao et al., 1998;He et al., 2011;Pomar et al., 2012). ...
