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Fig. 11. Depositional-dip profiles across ancient delta-scale subaqueous clinoforms: (BK) Upper Cretaceous Blackhawk Formation subaerial delta clinoforms and linked Mancos Shale sub- aqueous delta clinoforms, Western Interior Basin, onshore USA (after Hampson (2010)); (BR) Lower Jurassic Bridport Sand Formation subaerial delta clinoforms and linked Down Cliff Clay subaqueous delta clinoforms, Wessex Basin, onshore UK (after Morris et al. (2006); Hampson et al. (in press)); (SG) Upper Jurassic Sognefjord Formation subaqueous delta clinoforms, North Sea Basin, offshore Norway (after Patruno et al. (2013b)); (MN) Upper Miocene calcareous grainstones, Menorcan platform (Spain), Mediterranean Basin (after Pomar et al. (2002)). diverging from the topset to the foreset and converging again towards the bottomset (Kuehl et al., 1997). The clinoform foreset is formed by graded sandy-silty laminae interbedded with clay laminae. The coarsest-grained layers are presumably deposited by sediment-laden underflows generated during tropical storms, with up to 8 m thick mass flows created in the subaqueous delta front area by episodic earth- quakes or storms (Michels et al., 1998). These last deposits are imaged in seismic reflection profiles as transparent units (Palamenghi et al., 2011). The subaqueous clinoform is actively prograding every year by ca. 12-17 m across the Bengal Shelf. Sediment becomes increasingly finer-grained offshore and westwards, which in combination with analyses of seabed palaeocurrent indicators, suggests that subaqueous clinoforms have been fed by westward-flowing cyclonic currents that transport sediment fed by the Ganges-Brahamaputra river mouth alongshore and offshore (Kuehl et al., 1997). A large canyon, known as ‘Swatch of No Ground’, deeply dissects the shelf and the subaqueous

Figure 11 Depositional-dip profiles across ancient delta-scale subaqueous clinoforms: (BK) Upper Cretaceous Blackhawk Formation subaerial delta clinoforms and linked Mancos Shale sub- aqueous delta clinoforms, Western Interior Basin, onshore USA (after Hampson (2010)); (BR) Lower Jurassic Bridport Sand Formation subaerial delta clinoforms and linked Down Cliff Clay subaqueous delta clinoforms, Wessex Basin, onshore UK (after Morris et al. (2006); Hampson et al. (in press)); (SG) Upper Jurassic Sognefjord Formation subaqueous delta clinoforms, North Sea Basin, offshore Norway (after Patruno et al. (2013b)); (MN) Upper Miocene calcareous grainstones, Menorcan platform (Spain), Mediterranean Basin (after Pomar et al. (2002)). diverging from the topset to the foreset and converging again towards the bottomset (Kuehl et al., 1997). The clinoform foreset is formed by graded sandy-silty laminae interbedded with clay laminae. The coarsest-grained layers are presumably deposited by sediment-laden underflows generated during tropical storms, with up to 8 m thick mass flows created in the subaqueous delta front area by episodic earth- quakes or storms (Michels et al., 1998). These last deposits are imaged in seismic reflection profiles as transparent units (Palamenghi et al., 2011). The subaqueous clinoform is actively prograding every year by ca. 12-17 m across the Bengal Shelf. Sediment becomes increasingly finer-grained offshore and westwards, which in combination with analyses of seabed palaeocurrent indicators, suggests that subaqueous clinoforms have been fed by westward-flowing cyclonic currents that transport sediment fed by the Ganges-Brahamaputra river mouth alongshore and offshore (Kuehl et al., 1997). A large canyon, known as ‘Swatch of No Ground’, deeply dissects the shelf and the subaqueous

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Fig. 1. Compound clinoform systems at different scales. (A) Idealized regional cross-section parallel to regional depositional dip, showing three actively growing clinoforms systems: del! shelf-prism and continental-margin clinoforms (modified after Henriksen et al. (2009)). (B) Cross-sectional profile parallel to depositional dip showing a typical delta-scale compout clinoform system (located in Fig. 1A), comprising subaerial delta and subaqueous delta clinoforms (modified after Helland-Hansen and Hampson (2009)).
Fig. 1. Compound clinoform systems at different scales. (A) Idealized regional cross-section parallel to regional depositional dip, showing three actively growing clinoforms systems: del! shelf-prism and continental-margin clinoforms (modified after Henriksen et al. (2009)). (B) Cross-sectional profile parallel to depositional dip showing a typical delta-scale compout clinoform system (located in Fig. 1A), comprising subaerial delta and subaqueous delta clinoforms (modified after Helland-Hansen and Hampson (2009)).
Fig. 3. The three main types of delta-scale clinoform configurations, with reference to their characteristic depositional profiles on the western Adriatic shelf (Cattaneo et al., 2003, 2007; Correggiari et al., 2005). (A) Isolated subaerial delta clinoforms, such as at the mouth of the present-day Po River; (B) delta-scale compound clinoforms, comprising a shoreline or subaerial delta clinoform and a time-equivalent subaqueous delta clinoform, formed along the western Adriatic shelf to the south of the Po River mouth; (C) isolated subaqueous delta clinoform offshore of the Gargano peninsula on the south-western Adriatic shelf, onlapping onto a pre-existing erosional substrate.
Fig. 3. The three main types of delta-scale clinoform configurations, with reference to their characteristic depositional profiles on the western Adriatic shelf (Cattaneo et al., 2003, 2007; Correggiari et al., 2005). (A) Isolated subaerial delta clinoforms, such as at the mouth of the present-day Po River; (B) delta-scale compound clinoforms, comprising a shoreline or subaerial delta clinoform and a time-equivalent subaqueous delta clinoform, formed along the western Adriatic shelf to the south of the Po River mouth; (C) isolated subaqueous delta clinoform offshore of the Gargano peninsula on the south-western Adriatic shelf, onlapping onto a pre-existing erosional substrate.
Fig. 4. Three-dimensional scheme portraying the main architectural features and the typical oceanographic environment of present-day delta-scale compound clinoforms, such as tt western Adriatic shelf (Cattaneo et al., 2003, 2007) and the western Yellow Sea (Liu et al., 2006, 2007). Shore-parallel coastal currents contribute to the uniform growth of the subaqueot clinoform, by along-shelf redistribution of sediments fed by fluvial input points. Offshore currents influence the overall shore-parallel strike-direction of the subaqueous clinoform Downwelling currents transport shoreface sediments offshore, thereby sustaining the overall growth and progradation of the subaqueous clinoform perpendicular to the alongshore cu rents that feed it. In well-documented modern examples, the position of subaqueous clinoform bottomsets is controlled by seafloor-hugging offshore currents flowing parallel to tt clinoform strike and/or by upwelling processes, which force sediment transport along clinoform strike rather than offshore (e.g., Cattaneo et al., 2003, 2007; Liu et al., 2006, 2007).
Fig. 4. Three-dimensional scheme portraying the main architectural features and the typical oceanographic environment of present-day delta-scale compound clinoforms, such as tt western Adriatic shelf (Cattaneo et al., 2003, 2007) and the western Yellow Sea (Liu et al., 2006, 2007). Shore-parallel coastal currents contribute to the uniform growth of the subaqueot clinoform, by along-shelf redistribution of sediments fed by fluvial input points. Offshore currents influence the overall shore-parallel strike-direction of the subaqueous clinoform Downwelling currents transport shoreface sediments offshore, thereby sustaining the overall growth and progradation of the subaqueous clinoform perpendicular to the alongshore cu rents that feed it. In well-documented modern examples, the position of subaqueous clinoform bottomsets is controlled by seafloor-hugging offshore currents flowing parallel to tt clinoform strike and/or by upwelling processes, which force sediment transport along clinoform strike rather than offshore (e.g., Cattaneo et al., 2003, 2007; Liu et al., 2006, 2007).
Clinoforms and clinoform sets analysed using measurements taken from published literature compilations (i.e. not directly measured by the authors). Abbreviations are used in Figs. 6-11. Clinoform topset and foreset slope gradients ar equate to the parameters ‘average delta plain gradient’ and ‘average upper delta slope gradient’ of Orton and Reading (1993). Delta bottomset slopes are assumed to equate to average shelf gradient (e.g., Olariu and Steel, 2009). Cla subaerial delta type is after Orton and Reading (1993), and is based on both dominant grain size (GR =m gravelly sand; FS = fine-grained sand; MS = mud-silt) and dominant depositional processes (i = input; w = wave; t = tide are cited as follows: (a) Orton and Reading (1993); (b) Burgess and Hovius (1998); (c) Olariu and Steel (2009); (d) Howell et al. (2008); (e) Bristow and Pucillo (2006).
Clinoforms and clinoform sets analysed using measurements taken from published literature compilations (i.e. not directly measured by the authors). Abbreviations are used in Figs. 6-11. Clinoform topset and foreset slope gradients ar equate to the parameters ‘average delta plain gradient’ and ‘average upper delta slope gradient’ of Orton and Reading (1993). Delta bottomset slopes are assumed to equate to average shelf gradient (e.g., Olariu and Steel, 2009). Cla subaerial delta type is after Orton and Reading (1993), and is based on both dominant grain size (GR =m gravelly sand; FS = fine-grained sand; MS = mud-silt) and dominant depositional processes (i = input; w = wave; t = tide are cited as follows: (a) Orton and Reading (1993); (b) Burgess and Hovius (1998); (c) Olariu and Steel (2009); (d) Howell et al. (2008); (e) Bristow and Pucillo (2006).
Fig. 5. Summary of clinoform nomenclature, illustrated for a delta-scale subaqueous clinoform (Fig. 1B). The clinoform inflection point is the point where the gradient reaches maximum values. The inflection zone is defined as a relatively small area around the inflection point, and it is often a more readily observable parameter. The rollover points are the two points of maximum curvature located landward and seaward of the inflection point. The rollover points separate a foreset of steeper gradient from the landward-lying topset and seaward-lying bottomset, which both have gentler gradients. The toe of the clinoform occurs in the bottomset, where the clinoform becomes conformable with the underlying substrate. The clinoform height (H,,) is the difference in elevation between the clinoform toe point and the clinoform head point, where the topset becomes conformable with the underlying substrate. Additional parameters are described in the text. Vertical sediment accumulation rate is considered to be the maxi- mum vertical thickness of a clinothem divided by the age difference between the basal and top clinoform surface, which usually corresponds to flooding surfaces. Progradation rate in recent clinoforms is measured as the horizontal distance between the inflection point positions of two dated clinoforms divided by their age difference. Wherever possible for ancient clinoform successions, progradation rate was measured by fol- lowing the method proposed by Patruno et al. (in press). Progradation resistance ratio is a dimensionless number corre- sponding to the ratio between mean vertical sediment accumulation rate and progradation rate calculated along a cross section parallel to the clinoform dip (cf, Patruno et al., in press). This ratio reflects the In this work, several clinoform architectural and geochronological parameters have been measured from published cross-sections, maps and other data (Fig. 6, Tables 1 and 2). Below, and in Fig. 5, these param- eters are briefly defined. On the cross-sectional profile of a clinoform surface, two points of maximum curvature (‘rollover points’) are usually located landward and basinward of the point of maximum slope gradi- ent (‘inflection point’; Fig. 5). Upper and lower rollover points are centred respectively on the upward-convex topset-to-foreset transition of a clinoform surface (e.g., Fig. 1A-B) and on the upward-concave foreset-to-bottomset transition of a clinoform surface. The positions of these two prominent breaks-in-slope subdivide the clinoform surface into a steeper central area (‘foreset’) and two gently-sloping areas, respectively landward (‘topset’) and basinward (‘bottomset’ or ‘toeset’) of the rollover points (Barrell, 1912; Mitchum et al., 1977; Pirmez et al.,
Fig. 5. Summary of clinoform nomenclature, illustrated for a delta-scale subaqueous clinoform (Fig. 1B). The clinoform inflection point is the point where the gradient reaches maximum values. The inflection zone is defined as a relatively small area around the inflection point, and it is often a more readily observable parameter. The rollover points are the two points of maximum curvature located landward and seaward of the inflection point. The rollover points separate a foreset of steeper gradient from the landward-lying topset and seaward-lying bottomset, which both have gentler gradients. The toe of the clinoform occurs in the bottomset, where the clinoform becomes conformable with the underlying substrate. The clinoform height (H,,) is the difference in elevation between the clinoform toe point and the clinoform head point, where the topset becomes conformable with the underlying substrate. Additional parameters are described in the text. Vertical sediment accumulation rate is considered to be the maxi- mum vertical thickness of a clinothem divided by the age difference between the basal and top clinoform surface, which usually corresponds to flooding surfaces. Progradation rate in recent clinoforms is measured as the horizontal distance between the inflection point positions of two dated clinoforms divided by their age difference. Wherever possible for ancient clinoform successions, progradation rate was measured by fol- lowing the method proposed by Patruno et al. (in press). Progradation resistance ratio is a dimensionless number corre- sponding to the ratio between mean vertical sediment accumulation rate and progradation rate calculated along a cross section parallel to the clinoform dip (cf, Patruno et al., in press). This ratio reflects the In this work, several clinoform architectural and geochronological parameters have been measured from published cross-sections, maps and other data (Fig. 6, Tables 1 and 2). Below, and in Fig. 5, these param- eters are briefly defined. On the cross-sectional profile of a clinoform surface, two points of maximum curvature (‘rollover points’) are usually located landward and basinward of the point of maximum slope gradi- ent (‘inflection point’; Fig. 5). Upper and lower rollover points are centred respectively on the upward-convex topset-to-foreset transition of a clinoform surface (e.g., Fig. 1A-B) and on the upward-concave foreset-to-bottomset transition of a clinoform surface. The positions of these two prominent breaks-in-slope subdivide the clinoform surface into a steeper central area (‘foreset’) and two gently-sloping areas, respectively landward (‘topset’) and basinward (‘bottomset’ or ‘toeset’) of the rollover points (Barrell, 1912; Mitchum et al., 1977; Pirmez et al.,
Fig. 6. Location of recent and ancient clinoforms and clinoform sets analysed in this study. Bathymetry and topography are derived from the Global Multi-Resolution Topography dataset of Ryan et al. (2009), and are plotted using GeoMapApp freeware. Abbreviations for clinoforms and clinoform sets are given in Tables 1 and 2. Plan views and cross sections oriented parallel to the depositional dip of twenty recent delta-scale compound clinoforms are located in Fig. 6 and presented in Figs. 7-10 and in Table 3. These systems are either formed by deltaic systems (e.g., off the mouth of the Yangtze, Yellow- Shandong, Ganges-Brahmaputra, Amazon, Fly, Orinoco, Shoalhaven, Atchafalaya, Salinas, San Diego, Manawatu, Rhone, Tiber, Arno-Cecina and Italian Adriatic rivers), or are not directly related to river mouths (e.g., mid-shelf clinoforms off the coast of southern Spain, southern Portugal, south-eastern Australia, western Ascension Island). Detailed A wealth of publications exists for many recent delta-scale subaque- ous clinoforms and associated compound clinoforms. The reader is referred to Hori et al. (2001) and Liu et al. (2006, 2007) (Yangtze River delta); Bornhold et al. (1986), Alexander et al. (1991), Liu et al. (2004) and Yang and Liu (2007) (Yellow River delta and subaqueous Shandong delta); Kuehl et al. (1997, 2005), Michels et al. (1998), and Palamenghi et al. (2011) (Ganges-Brahmaputra River subaqueous delta); Kuehl et al. (1986), Nittrouer et al. (1986, 1996) and Methling et al. (1996) (Amazon River delta); Walsh et al. (2004) (Fly River delta); Warne et al. (2002) (Orinoco River delta); Neill and Allison (2005) (Atchafalaya delta); Amorosi and Milli (2001) and Correggiari et al. (2005) (Tiber and Po River deltas); Cattaneo et al. (2003, 2004, 2007) (Adriatic subaqueous clinoforms); Dunbar and Barrett (2005) (Manawatu coastlines, New Zealand); Field and Roy (1984) (south-eastern Australia coastlines); Hernandez-Molina et al. (2000a,b) and Lobo et al. (2005) (southern Spanish and Portuguese coastlines); and Chin et al. (1988) (Monterey Bay coastlines). Mitchell et al. (2012) provided a synthesis of delta-scale sand- prone subaqueous clinoforms (e.g., offshore of Manawatu, southern Spanish and Portuguese, and south-eastern Australia coastlines), as well as describing similar clinoforms off the coasts of western As- cension Island and Oceanside, USA. Some of the systems shown in Figs. 7-10 have not been previously investigated, but they contain
Fig. 6. Location of recent and ancient clinoforms and clinoform sets analysed in this study. Bathymetry and topography are derived from the Global Multi-Resolution Topography dataset of Ryan et al. (2009), and are plotted using GeoMapApp freeware. Abbreviations for clinoforms and clinoform sets are given in Tables 1 and 2. Plan views and cross sections oriented parallel to the depositional dip of twenty recent delta-scale compound clinoforms are located in Fig. 6 and presented in Figs. 7-10 and in Table 3. These systems are either formed by deltaic systems (e.g., off the mouth of the Yangtze, Yellow- Shandong, Ganges-Brahmaputra, Amazon, Fly, Orinoco, Shoalhaven, Atchafalaya, Salinas, San Diego, Manawatu, Rhone, Tiber, Arno-Cecina and Italian Adriatic rivers), or are not directly related to river mouths (e.g., mid-shelf clinoforms off the coast of southern Spain, southern Portugal, south-eastern Australia, western Ascension Island). Detailed A wealth of publications exists for many recent delta-scale subaque- ous clinoforms and associated compound clinoforms. The reader is referred to Hori et al. (2001) and Liu et al. (2006, 2007) (Yangtze River delta); Bornhold et al. (1986), Alexander et al. (1991), Liu et al. (2004) and Yang and Liu (2007) (Yellow River delta and subaqueous Shandong delta); Kuehl et al. (1997, 2005), Michels et al. (1998), and Palamenghi et al. (2011) (Ganges-Brahmaputra River subaqueous delta); Kuehl et al. (1986), Nittrouer et al. (1986, 1996) and Methling et al. (1996) (Amazon River delta); Walsh et al. (2004) (Fly River delta); Warne et al. (2002) (Orinoco River delta); Neill and Allison (2005) (Atchafalaya delta); Amorosi and Milli (2001) and Correggiari et al. (2005) (Tiber and Po River deltas); Cattaneo et al. (2003, 2004, 2007) (Adriatic subaqueous clinoforms); Dunbar and Barrett (2005) (Manawatu coastlines, New Zealand); Field and Roy (1984) (south-eastern Australia coastlines); Hernandez-Molina et al. (2000a,b) and Lobo et al. (2005) (southern Spanish and Portuguese coastlines); and Chin et al. (1988) (Monterey Bay coastlines). Mitchell et al. (2012) provided a synthesis of delta-scale sand- prone subaqueous clinoforms (e.g., offshore of Manawatu, southern Spanish and Portuguese, and south-eastern Australia coastlines), as well as describing similar clinoforms off the coasts of western As- cension Island and Oceanside, USA. Some of the systems shown in Figs. 7-10 have not been previously investigated, but they contain
Fig. 7. Maps showing plan-view features of present-day macro-scale shelfal settings where delta-scale compound clinoforms and/or subaqueous clinoforms are actively prograding. Maps and contours are taken from the Global Multi-Resolution Topography dataset of Ryan et al. (2009). Steeper subaqueous areas on the inner-to-mid-shelf (with respect to the surrounding low-gradient shelf) are highlighted by grey shading. The majority of these areas of steeper shelf gradient correspond to the foresets of actively growing clinoforms, whereas in other cases they may correspond to steep erosional surfaces. (A) Cross-sectional profiles shown in Figs. 3, 14 and 16 are located. (HH) Northern Yellow Sea shelf (North-east China and Korea), including the mouth of the Yellow River; (YG) Southern Yellow Sea shelf (eastern China), including the mouth of the Yangtze River; (GB) Indian Ocean shelf off the mouth of the Ganges-Brahmaputra River system (eastern India and Bangladesh) (AM) Western Southern Atlantic Ocean shelf, off the Amazon River mouth (north-eastern Brazil); (FLY) shelf off the southern coasts of Papua New Guinea, including off the Fly River mouth; (ON) Western Southern Atlantic Ocean shelf, off the Orinoco River mouth (eastern Venezuela); (AT & MI) Northern Gulf of Mexico shelf, off the mouth of the Mississippi and Atchafalaya rivers (southern Louisiana, U.S.); (AD) Adriatic Sea shelf, Italy, including the cross-sectional profiles of Po-, Adriatic- and Gargano-type clinoforms in Fig. 3 and the Adriatic Shelf bathymetric profile in Fig. 10. (B) Cross-sectional profiles shown in Figs. 2, 14 and 16 are located. (AR) Tuscany coastlines (Tyrrhenian Sea, north-western Italy), including the profiles off the mouths of Cecina and Arno rivers; (RH) Languedoc shelf (southern France, Western Mediterranean) off the Rhone River mouth; (TB) Tyrrhenian Sea Shelf off the Tiber River mouth (central-western Italy, Western Mediterranean); (SH) shelf off the Shoalhaven River mouth (south-eastern Australia coast); (FA) Eastern North Atlantic Ocean shelf off the coasts of southern Spain and Portugal (Faro-Guadiana). (C) Cross-sectional profiles shown in Figs. 14 and 15 are located. (MN) Manawatu coast (New Zealand); (PJ & BB) South-eastern Australia shelf, including Port Jackson and Bate Bay profiles; (MB) shelf off Monterey Bay, near the Salinas River mouth (California, U.S.A.); (OC) shelf off Oceanside, near the Sand Diego river mouth (California, U.S.A.); (AL) Western Mediterranean Shelf off the Cabo de Gata promontory (Almeria, southern Spain); (AS) Atlantic ocean off the western coastlines of Ascension Island.
Fig. 7. Maps showing plan-view features of present-day macro-scale shelfal settings where delta-scale compound clinoforms and/or subaqueous clinoforms are actively prograding. Maps and contours are taken from the Global Multi-Resolution Topography dataset of Ryan et al. (2009). Steeper subaqueous areas on the inner-to-mid-shelf (with respect to the surrounding low-gradient shelf) are highlighted by grey shading. The majority of these areas of steeper shelf gradient correspond to the foresets of actively growing clinoforms, whereas in other cases they may correspond to steep erosional surfaces. (A) Cross-sectional profiles shown in Figs. 3, 14 and 16 are located. (HH) Northern Yellow Sea shelf (North-east China and Korea), including the mouth of the Yellow River; (YG) Southern Yellow Sea shelf (eastern China), including the mouth of the Yangtze River; (GB) Indian Ocean shelf off the mouth of the Ganges-Brahmaputra River system (eastern India and Bangladesh) (AM) Western Southern Atlantic Ocean shelf, off the Amazon River mouth (north-eastern Brazil); (FLY) shelf off the southern coasts of Papua New Guinea, including off the Fly River mouth; (ON) Western Southern Atlantic Ocean shelf, off the Orinoco River mouth (eastern Venezuela); (AT & MI) Northern Gulf of Mexico shelf, off the mouth of the Mississippi and Atchafalaya rivers (southern Louisiana, U.S.); (AD) Adriatic Sea shelf, Italy, including the cross-sectional profiles of Po-, Adriatic- and Gargano-type clinoforms in Fig. 3 and the Adriatic Shelf bathymetric profile in Fig. 10. (B) Cross-sectional profiles shown in Figs. 2, 14 and 16 are located. (AR) Tuscany coastlines (Tyrrhenian Sea, north-western Italy), including the profiles off the mouths of Cecina and Arno rivers; (RH) Languedoc shelf (southern France, Western Mediterranean) off the Rhone River mouth; (TB) Tyrrhenian Sea Shelf off the Tiber River mouth (central-western Italy, Western Mediterranean); (SH) shelf off the Shoalhaven River mouth (south-eastern Australia coast); (FA) Eastern North Atlantic Ocean shelf off the coasts of southern Spain and Portugal (Faro-Guadiana). (C) Cross-sectional profiles shown in Figs. 14 and 15 are located. (MN) Manawatu coast (New Zealand); (PJ & BB) South-eastern Australia shelf, including Port Jackson and Bate Bay profiles; (MB) shelf off Monterey Bay, near the Salinas River mouth (California, U.S.A.); (OC) shelf off Oceanside, near the Sand Diego river mouth (California, U.S.A.); (AL) Western Mediterranean Shelf off the Cabo de Gata promontory (Almeria, southern Spain); (AS) Atlantic ocean off the western coastlines of Ascension Island.
Rhone delta, a compound clinoform interpretation is also supported by Holocene sediment isopach and grain-size maps published by Gensous and Tesson (1997), Tesson et al. (2000) and Labaune et al. (2005). Australia coastlines; Field and Roy, 1984). In most examples, it is possi- ble to distinguish a subaerial delta clinoform at the shoreline, a subaque- ous delta clinoform in the middle of the shelf, and a clinoform marking the shelf edge (shelf-prism or continental-margin clinoform). In most of the examples presented here, maps of Late Holocene sediment thick- ness support the interpretation of actively accreting clinoforms situated at the three present-day breaks in bathymetric gradient (e.g., Nittrouer et al., 1986; Gensous and Tesson, 1997; Michels et al., 1998; Cattaneo et al., 2003, 2007; Liu et al., 2004, 2007; Lobo et al., 2005; Yang and Liu, 2007; Le Dantec et al., 2010). Below, we summarise four represen- tative and particularly well-documented examples of recent delta- Bathymetric contours and cross sections in Figs. 7-10 have been drawn using the Global Multi-Resolution Topography dataset of Ryan et al. (2009), and areas of relatively steep gradient on the inner-to- mid-shelf have been highlighted in the maps by grey shading. These steep areas form shoreline-parallel belts that generally correspond to the foresets of actively accreting clinoforms, although in some cases they may correspond to steep erosional surfaces (e.g., south-eastern
Rhone delta, a compound clinoform interpretation is also supported by Holocene sediment isopach and grain-size maps published by Gensous and Tesson (1997), Tesson et al. (2000) and Labaune et al. (2005). Australia coastlines; Field and Roy, 1984). In most examples, it is possi- ble to distinguish a subaerial delta clinoform at the shoreline, a subaque- ous delta clinoform in the middle of the shelf, and a clinoform marking the shelf edge (shelf-prism or continental-margin clinoform). In most of the examples presented here, maps of Late Holocene sediment thick- ness support the interpretation of actively accreting clinoforms situated at the three present-day breaks in bathymetric gradient (e.g., Nittrouer et al., 1986; Gensous and Tesson, 1997; Michels et al., 1998; Cattaneo et al., 2003, 2007; Liu et al., 2004, 2007; Lobo et al., 2005; Yang and Liu, 2007; Le Dantec et al., 2010). Below, we summarise four represen- tative and particularly well-documented examples of recent delta- Bathymetric contours and cross sections in Figs. 7-10 have been drawn using the Global Multi-Resolution Topography dataset of Ryan et al. (2009), and areas of relatively steep gradient on the inner-to- mid-shelf have been highlighted in the maps by grey shading. These steep areas form shoreline-parallel belts that generally correspond to the foresets of actively accreting clinoforms, although in some cases they may correspond to steep erosional surfaces (e.g., south-eastern
Fig. 8. Bathymetric profiles of typical present-day delta-scale subaqueous clinoforms and compound clinoforms, drawn by utilizing the Global Multi-Resolution Topography dataset of Ryan et al. (2009): (A) macro-scale system, characterised by a horizontal distance between shoreline and subaqueous delta rollover point of > 10 km, and most commonly well in excess of 50 km (Fig. 7A); (B) meso-scale systems, with a horizontal distance between shoreline and subaqueous delta rollover point of ca. 7-10 km (Fig. 7B); and (C) micro-scale systems, characterised by a horizontal distance between shoreline and subaqueous delta rollover point of <7 km, and most often of only 1-2 km (Fig. 7C). The horizontal grey bars highlight the water depth ranges for subaqueous clinoform rollover points in macro-, meso- and micro-scale systems, respectively.
Fig. 8. Bathymetric profiles of typical present-day delta-scale subaqueous clinoforms and compound clinoforms, drawn by utilizing the Global Multi-Resolution Topography dataset of Ryan et al. (2009): (A) macro-scale system, characterised by a horizontal distance between shoreline and subaqueous delta rollover point of > 10 km, and most commonly well in excess of 50 km (Fig. 7A); (B) meso-scale systems, with a horizontal distance between shoreline and subaqueous delta rollover point of ca. 7-10 km (Fig. 7B); and (C) micro-scale systems, characterised by a horizontal distance between shoreline and subaqueous delta rollover point of <7 km, and most often of only 1-2 km (Fig. 7C). The horizontal grey bars highlight the water depth ranges for subaqueous clinoform rollover points in macro-, meso- and micro-scale systems, respectively.
Fig. 9. Plots of morphological parameters of recent deltaic compound clinoforms and delta-scale subaqueous clinoforms (Figs. 11-14): (A) subaqueous clinoform foreset gradient versus subaerial clinoform foreset gradient; (B) ratio of subaerial to subaqueous clinoform heights versus average shelf gradient; and (C) distance from shoreline of shelf-edge break versus distance from shoreline of subaqueous rollover point. Abbreviations for clinoforms and clinoform sets are introduced in Tables 1 and 2.
Fig. 9. Plots of morphological parameters of recent deltaic compound clinoforms and delta-scale subaqueous clinoforms (Figs. 11-14): (A) subaqueous clinoform foreset gradient versus subaerial clinoform foreset gradient; (B) ratio of subaerial to subaqueous clinoform heights versus average shelf gradient; and (C) distance from shoreline of shelf-edge break versus distance from shoreline of subaqueous rollover point. Abbreviations for clinoforms and clinoform sets are introduced in Tables 1 and 2.
Fig. 10. Depositional-dip profiles across recent delta-scale subaqueous clinoforms: (PO) Po subaerial delta clinoform and linked (GA) Gargano subaqueous delta clinoform (afte1 Correggiari et al. (2005); Cattaneo et al. (2003, 2007)); (YGs) subaqueous clinoform off the Yangtze River delta (after Liu et al. (2007)); (GBs) subaqueous clinoform off the Ganges- Brahmaputra River delta (after Palamenghi et al. (2011)); (AL) subaqueous clinoform off Cabo de Gata shoreline, southern Spain (after Hernandez-Molina et al. (2000a)).
Fig. 10. Depositional-dip profiles across recent delta-scale subaqueous clinoforms: (PO) Po subaerial delta clinoform and linked (GA) Gargano subaqueous delta clinoform (afte1 Correggiari et al. (2005); Cattaneo et al. (2003, 2007)); (YGs) subaqueous clinoform off the Yangtze River delta (after Liu et al. (2007)); (GBs) subaqueous clinoform off the Ganges- Brahmaputra River delta (after Palamenghi et al. (2011)); (AL) subaqueous clinoform off Cabo de Gata shoreline, southern Spain (after Hernandez-Molina et al. (2000a)).
Parameters extracted from the Global Multi-Resolution Topography bathymetric dataset (Ryan et al., 2009), for present-day delta-scale compound clinoform systems (Figs. 7-10). Th range refers to the 5- to 95-percentile of the statistical distribution. Table 3
Parameters extracted from the Global Multi-Resolution Topography bathymetric dataset (Ryan et al., 2009), for present-day delta-scale compound clinoform systems (Figs. 7-10). Th range refers to the 5- to 95-percentile of the statistical distribution. Table 3
Fig. 12. Plots of clinoform morphological parameters. Different clinoform types tend to plot in different, but overlapping, fields. See Fig. 5 for units and clinoform nomenclature. slumping and high Holocene sedimentation rate (ca. 500 m/kyr) near the canyon head (Kuehl et al., 1986, 1997; Weber et al., 1997; Michels et al., 1998). Palamenghi et al (2011) suggest that sediment deposition towards the western part of the subaqueous delta has increased in the last few centuries, with subsequent higher sediment export to the deep-water fan through the ‘Swatch of No Ground’ canyon. delta front (Fig. 7A-GB). This canyon captures most of the sediment load carried by the westward-flowing cyclonic currents, allowing shelf bypass of >35% of the fluviatile sediment load towards the deep- marine Bengal Fan. This oceanographic configuration has caused off- shelf sediment transport and turbidite deposition to the slope and basin-floor during the Holocene highstand, together with growth faults,
Fig. 12. Plots of clinoform morphological parameters. Different clinoform types tend to plot in different, but overlapping, fields. See Fig. 5 for units and clinoform nomenclature. slumping and high Holocene sedimentation rate (ca. 500 m/kyr) near the canyon head (Kuehl et al., 1986, 1997; Weber et al., 1997; Michels et al., 1998). Palamenghi et al (2011) suggest that sediment deposition towards the western part of the subaqueous delta has increased in the last few centuries, with subsequent higher sediment export to the deep-water fan through the ‘Swatch of No Ground’ canyon. delta front (Fig. 7A-GB). This canyon captures most of the sediment load carried by the westward-flowing cyclonic currents, allowing shelf bypass of >35% of the fluviatile sediment load towards the deep- marine Bengal Fan. This oceanographic configuration has caused off- shelf sediment transport and turbidite deposition to the slope and basin-floor during the Holocene highstand, together with growth faults,
Fig. 15. Plots of parameter pairs showing moderate-to-strong (R? > 0.5) statistical correlations. Red and yellow best-fit lines correspond to correlations for all clinoforms and sand-pron subaqueous delta clinoforms, respectively. Equations for the best-fit lines are numbered in the grey boxes in each plot; these equations and values of the coefficient of determination (R? describing each best-fit line are given in Tables 5 and 7. See Fig. 5 for units and clinoform nomenclature.
Fig. 15. Plots of parameter pairs showing moderate-to-strong (R? > 0.5) statistical correlations. Red and yellow best-fit lines correspond to correlations for all clinoforms and sand-pron subaqueous delta clinoforms, respectively. Equations for the best-fit lines are numbered in the grey boxes in each plot; these equations and values of the coefficient of determination (R? describing each best-fit line are given in Tables 5 and 7. See Fig. 5 for units and clinoform nomenclature.
Typical value ranges for the statistical parameters examined within the clinoform population shown in Tables 1 and 2. For each clinoform type, the value ranges refer to the 5- to 95-percentile of the parameter statistical distribution. In order to show chronostratigraphically-constrained rate values that can be readily compatible with the short-term (<10 kyr) data obtained for muddy subaqueous clinoforms, both short-term (<10 kyr) and longer term (>10 kyr) rates for the other delta-scale clinoforms are displayed in this table. (*) = The foreset gradient of sandy deltas is 0.1-2.7° if Gilbert-type deltas are not considered. However, if small-scale, steep, high-latitude Gilbert deltas are added to the dataset (i.e. Alta, Bella Coola, c.f. Table 2), the 5-95 percentile range of foreset gradients increases to 10°.
Typical value ranges for the statistical parameters examined within the clinoform population shown in Tables 1 and 2. For each clinoform type, the value ranges refer to the 5- to 95-percentile of the parameter statistical distribution. In order to show chronostratigraphically-constrained rate values that can be readily compatible with the short-term (<10 kyr) data obtained for muddy subaqueous clinoforms, both short-term (<10 kyr) and longer term (>10 kyr) rates for the other delta-scale clinoforms are displayed in this table. (*) = The foreset gradient of sandy deltas is 0.1-2.7° if Gilbert-type deltas are not considered. However, if small-scale, steep, high-latitude Gilbert deltas are added to the dataset (i.e. Alta, Bella Coola, c.f. Table 2), the 5-95 percentile range of foreset gradients increases to 10°.
Fig. 16. Delta-scale compound clinoforms plotted on the tripartite classification scheme of Galloway (1975) for deltas. An arrow links each subaerial delta with its subaqueous delta coun- terpart. The positions of the subaerial delta clinoforms are derived from Orton and Reading (1993) and Galloway (1975). Approximate positions of the corresponding subaqueous delta clinoforms are inferred from the magnitude of waves and tides in the receiving basins for modern systems and from core-based facies analysis for ancient systems (supporting references listed in Tables 1 and 2). Qualitative changes in plan-view morphology of coeval subaerial and subaqueous delta clinoforms are also shown, and related to spatial changes in sedimentary processes.
Fig. 16. Delta-scale compound clinoforms plotted on the tripartite classification scheme of Galloway (1975) for deltas. An arrow links each subaerial delta with its subaqueous delta coun- terpart. The positions of the subaerial delta clinoforms are derived from Orton and Reading (1993) and Galloway (1975). Approximate positions of the corresponding subaqueous delta clinoforms are inferred from the magnitude of waves and tides in the receiving basins for modern systems and from core-based facies analysis for ancient systems (supporting references listed in Tables 1 and 2). Qualitative changes in plan-view morphology of coeval subaerial and subaqueous delta clinoforms are also shown, and related to spatial changes in sedimentary processes.
Fig. 17. Typical cross-sectional morphologies of mud- and sand-prone delta-scale compound clinoforms. The summarised differences between these two end-members are based on the anal- ysis shown in Figs. 13-16 and Tables 2 and 8, and discussed in the text. Both types of compound clinoform are usually characterised by oblique subaerial delta clinoform morphologies and sigmoidal subaqueous clinoform morphologies. Intermediate systems between these two end members exist. In particular there are several examples of relatively sand-rich subaerial deltas associated with muddy subaqueous counterparts (e.g., Po, Ganges-Brahamaputra, c.f. Fig. 16). Muddy subaerial deltas associated with sandy subaqueous deltas have not been reported.
Fig. 17. Typical cross-sectional morphologies of mud- and sand-prone delta-scale compound clinoforms. The summarised differences between these two end-members are based on the anal- ysis shown in Figs. 13-16 and Tables 2 and 8, and discussed in the text. Both types of compound clinoform are usually characterised by oblique subaerial delta clinoform morphologies and sigmoidal subaqueous clinoform morphologies. Intermediate systems between these two end members exist. In particular there are several examples of relatively sand-rich subaerial deltas associated with muddy subaqueous counterparts (e.g., Po, Ganges-Brahamaputra, c.f. Fig. 16). Muddy subaerial deltas associated with sandy subaqueous deltas have not been reported.
Strength of correlation between each possible pair of statistical parameters within the global clinoform dataset. Weak-to-strong positive correlations (R? > 0.1) are shown by light grey boxes, and weak-to-strong negative correlations by dark grey boxes. Moderate-to-strong correlations (R? > 0.5) are indicated by numbers, each corresponding to an equation in Tables ¢ and 7 and Fig. 9-10.
Strength of correlation between each possible pair of statistical parameters within the global clinoform dataset. Weak-to-strong positive correlations (R? > 0.1) are shown by light grey boxes, and weak-to-strong negative correlations by dark grey boxes. Moderate-to-strong correlations (R? > 0.5) are indicated by numbers, each corresponding to an equation in Tables ¢ and 7 and Fig. 9-10.
Strength of correlation between each possible pair of statistical parameters within the dataset of sand-prone subaqueous delta clinoforms. Weak-to-strong positive correlations (R? > 0.1) are shown by light grey boxes, and weak-to-strong negative correlations by dark grey boxes. Moderate-to-strong correlations (R? > 0.5) correlations are indicated by numbers, each cor- responding to an equation in Tables 6 and 7 and Figs. 9-10. Parameter pairs characterised by absence of correlation whereas in the global dataset (Table 5) a correlation exist (and vice versa) are highlighted by an asterisk (*). A double asterisk (**) marks parameter pairs showing an opposite correlation type than in the global dataset (cf. Table 5).
Strength of correlation between each possible pair of statistical parameters within the dataset of sand-prone subaqueous delta clinoforms. Weak-to-strong positive correlations (R? > 0.1) are shown by light grey boxes, and weak-to-strong negative correlations by dark grey boxes. Moderate-to-strong correlations (R? > 0.5) correlations are indicated by numbers, each cor- responding to an equation in Tables 6 and 7 and Figs. 9-10. Parameter pairs characterised by absence of correlation whereas in the global dataset (Table 5) a correlation exist (and vice versa) are highlighted by an asterisk (*). A double asterisk (**) marks parameter pairs showing an opposite correlation type than in the global dataset (cf. Table 5).
Table 7
Table 7
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Earth SciencesHolocene Evolution of Deltas
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