The Natural Range of Submarine Canyon-And-Channel Longitudinal Proﬁ Les

Exploring the Deep Sea and Beyond themed issue

The natural range of submarine canyon-and-channel longitudinal proﬁ les

Jacob A. Covault*, Andrea Fildani, Brian W. Romans, and Tim McHargue Chevron Energy Technology Company, Clastic Stratigraphy Research and Development, 6001 Bollinger Canyon Road, San Ramon, California 94583, USA

ABSTRACT and Tucker, 1999; Schumm et al., 2000). In and implications for models of continental mar- contrast, previous work on submarine canyon- gins, this study reviews canyon-and-channel We differentiated 20 submarine canyon- and-channel profi les has been predominantly longitudinal profi les from a global range of and-channel longitudinal profi les across limited to case studies of profi les from a single continental margins—from the tectonically various types of continental margins on the type of continental margin (e.g., Goff, 2001; active transform and convergent margins of the basis of relative convexity or concavity, and Estrada et al., 2005; Mitchell, 2005; Noda et al., Pacifi c to the Atlantic passive margin offshore according to their similarities to best-fi tting 2008; Gerber et al., 2009). Tectonic and sedi- the Americas (Fig. 1 and Table 1). We differen- mathematical functions. Profi les are visually mentary infl uences inherent to different types of tiated longitudinal profi les across continental differentiated into convex, slightly concave, continental margins, however, have a signifi cant slopes on the basis of (1) relative convexity or and very concave groups, each of which gen- impact on seascape morphology and sediment– concavity from visual inspection and (2) accord- erally corresponds with a continental-margin gravity-fl ow erosion and deposition by control- ing to their similarities to best-fi tting mathemat- type and distinct depositional architecture. ling the gradient and stability of the seafl oor, ical functions. These observations and analyses Profi le groups generally refl ect the competing and sediment caliber and supply (Bouma et al., provide a catalog of the breadth and general infl uences of uplift and construction of depo- 1985; Normark, 1985; Stow et al., 1985; Mutti controls of the shapes of submarine sediment- sitional relief of the seafl oor and its degra- and Normark, 1987; Shanmugam and Moiola, delivery systems, which can be related to the dation by erosion related to mass wasting. 1988; Normark and Piper, 1991; Carvajal et al., depositional architecture of different continen- Longitudinal-profi le shape provides a basis 2009; Piper and Normark, 2009). tal margins. for classifying deep-sea sedimentary systems, Bill Normark pioneered work on seafl oor linking them to the geomorphic processes canyon-and-channel systems and depositional Database and Methodology that shape continental margins. fans in 1970 with “Growth Patterns of Deep- Sea Fans” (Normark, 1970). This seminal work Our submarine canyon-and-channel database INTRODUCTION prompted Normark to reconcile seafl oor obser- includes 20 longitudinal profi les from a variety vations and interpretations of sediment–gravity- of continental margins (Figs. 1 and 2; Table 1). Submarine canyon-and-channel systems are fl ow processes with “ancient” buried subsurface These canyon-and-channel systems are sub- conduits through which sediment is transported and outcropping systems (e.g., 1982 COMFAN marine conduits that pass from predominantly across continental margins to deep-sea basins [COMmittee on FANs]; Bouma et al., 1985; erosional, V-shaped canyons indenting the shelf by sediment gravity fl ows and other mass move- Normark, 1985; Normark et al., 1985a; Mutti and uppermost slope to U-shaped channels with ments (Shepard, 1948, 1981; Menard, 1955). and Normark, 1987, 1991; Normark and Piper, overbank deposits across the lower slope and Processes that sculpted canyon-and-channel 1991; Normark et al., 1993). These efforts pro- continental rise (cf. Shepard, 1948; Menard, systems during their lifetimes are manifested in duced broadly applicable models of sediment 1955; Normark, 1970). We examined pro- the shapes of longitudinal profi les. Longitudinal dispersal across continental margins that hold fi les of canyons and channels that are present profi les of fl uvial systems have been contem- true to this day. Normark (1985) and Mutti across the modern seafl oor (i.e., buried chan- plated by geomorphologists since the nineteenth and Normark (1987) highlighted that the char- nel features are excluded) and, as such, they century (e.g., Playfair, 1802; Gilbert, 1880). acteristics of deep-water canyon-and-channel represent the most recent canyon-and-channel- Subsequent studies of fl uvial profi les have high- systems and depositional fans are controlled by system activity (i.e., since the last glacial cycle, lighted the relative importance of intrinsic and the morphology and sediment supply character- <100 ka, for many systems; Lambeck and extrinsic controlling variables, including water istics of the submarine continental margin and Chappell, 2001). Four canyon-and-channel pro- discharge, sediment supply, sediment caliber receiving basin. Multiple continental-margin fi les from the Cali fornia Continental Border- (Snow and Slingerland, 1987), and changing and receiving-basin scenarios and resultant land, La Jolla (14), Carlsbad (15), Oceanside uplift conditions. Interactions between these deep-water seafl oor and ancient stratigraphic (16), and Newport (17), were measured from variables introduce complications into the architectures were recognized in an attempt to National Oceanic and Atmospheric Admin- characteristic logarithmic, or concave upward, place a global and temporal breadth of turbidite istration/National Geophysical Data Center shape of terrestrial fl uvial profi les (Whipple architectures (i.e., seafl oor, buried subsurface, (NOAA/NGDC) and U.S. Geological Survey and outcropping) within a common framework (USGS) multibeam bathymetry (<3 arc-second *Present address: U.S. Geological Survey Eastern (Mutti and Normark, 1987). grids, 10-cm vertical resolution; Gardner and Energy Resources Science Center, 12201 Sunrise Following in the footsteps of Normark and Dartnell, 2002; Dartnell et al., 2007; Divins Valley Drive, Reston, Virginia 20192, USA. colleagues’ seminal work on seafl oor features and Metzger, 2009; Table 1). The Mississippi

Geosphere; April 2011; v. 7; no. 2; p. 313–332; doi: 10.1130/GES00610.1; 10 ﬁ gures; 1 table.

19 20 7 8 13 18 5 9 17 6 16 1 15 10 Figure 1. Location map of can- 14 3 yon-and-channel systems ana- 12 lyzed in this study. Numbers 2 correspond to systems in Table 1 11 and throughout the text.

profi le (10) was measured from NOAA/NGDC canyon-and-channel lengths and depths. To [11], and Amazon [12]) are only slightly con- multibeam bathymetry (Divins and Metzger, rectify this problem, we have normalized lon- cave in their proximal reaches (<0.4 of their 2009; Table 1). We chose to measure the pro- gitudinal profi les in two ways: (1) on the basis total down-system length) relative to profi les fi les of these fi ve canyon-and-channel systems of profi le length from canyon head to the end from the margin offshore southern California, because (1) readily available high-resolution of the confi ned portion of the system (e.g., at which are characterized by steeper slopes and multibeam bathymetry covers their extents the channel-to-lobe transition zone of Mutti and narrower shelves (e.g., La Jolla [14], Carls- from the continental shelf out to the base of Normark, 1987; Fig. 4); and (2) on the more bad [15], Oceanside [16], Newport [17], and slope and (2) satisfactory published profi les objective basis of profi le length from canyon Ascension [19]) (Fig. 4B). were not discovered during the course of our head to the point where profi les reached gradi- All 20 of the profi les used in this study were literature review. The remaining profi les were ents <0.25° and curvatures (i.e., down-system normalized across their continental slopes compiled from published examples to facilitate change in gradient) between –10–7 and 10–7. (Fig. 5). This normalization procedure cuts further investigation of the canyons and chan- This second method focuses on the lengths of off the relatively long and fl at tail of a few of nels of this study (Table 1). The majority of pro- canyon-and-channel systems across their con- the longest profi les, which extend across basin fi les were measured by other researchers from tinental slopes rather than their lengths across plains (e.g., Mississippi [10], Zaire [11], and high-resolution multibeam bathymetric data relatively fl at basin plains (cf. Adams and Amazon [12]) (Fig. 2). This is necessary in (Table 1). The exact reference for each pub- Schlager, 2000) (Fig. 5). order to compare their reaches across slopes to lished canyon-and-channel longitudinal profi le Three problems arose when we attempted to other systems, which do not extend as far across used in this study is emboldened and italicized normalize profi les across their predominantly the basin plain and are predominantly restricted in Table 1. Regardless of the resolution of pub- confi ned segments (e.g., from canyon head to to the slope. As mentioned above, the base of lished longitudinal profi les, long and short pro- the channel-to-lobe transition): (1) not all of slope was not measured at an arbitrary or unit fi les are compared at similar resolutions as a the profi les include the entire confi ned seg- length; rather, it was defi ned at the point where result of the following measurement procedure: ments of their canyon-and-channel systems profi les reached gradients <0.25° and curva- (1) water depths and down-system lengths were (i.e., many published examples and bathy- tures between –10–7 and 10–7 (cf. Adams and measured along every bend (cf. channel length metric data sets do not extend at suffi ciently Schlager, 2000) (Fig. 2). Here, we include all and slope measurements of Flood and Damuth, high resolution beyond the continental slope); normalized longitudinal-profi le data; however, 1987); and (2) water depths and down-system (2) the exact locations of confi ned-to-uncon- we focus on normalization across the slope in lengths of the high-resolution profi les were fi ned transitions are commonly poorly defi ned, order to provide a more inclusive comparison resampled every 10 km for systems >100 km gradational sedimentary environments and, as of profi les (Fig. 5). long and every 1 km for systems <100 km long. a result, are subjective; and (3) even though Gradient and curvature (down-system change profi les were from different continental mar- Longitudinal-Profi le Groups and in gradient) were also calculated. gins, with very different tectonic and sedimen- Curve-Fitting Functions tary controls on their development, they only Longitudinal-Profi le Normalization fell into two groups of longitudinal profi les— Normalized longitudinal profiles were convex upward and concave upward (Fig. 4A). grouped in two ways: (1) on the basis of relative Figure 3 shows all the longitudinal profi les Regarding problem 3, closer inspection of con- convexity or concavity from visual inspection; used in this study. These are diffi cult to com- cave upward profi les shows that profi les from and (2) according to their similarities to best- pare to one another because of differences in mature passive margins (e.g., Rhone [8], Zaire fi tting mathematical functions (cf. Shepherd,

314 Geosphere, April 2011 Canyon-and-channel longitudinal profi les ) continued ( Yes; driven gravity- (<3 arc- Mud rich resolution) bathymetry second grids; NOAA/NGDC 10-cm vertical Gulf of Mexico ,17,26 2,29 5 mud rich SeaBeam over 5 km) (measured bathymetry Mud to gravel; Atlantic Ocean New Jersey, USA, New Jersey, See references list at the bottom of ,29 ne- 25 Sea dner and Dartnell, 2002; Dartnell et al., 2007; Mixed* Passive Passive silt rich France, bathymetry Mud to fi SeaMARC I grained sand; 1980s-vintage SeaBeam and Mediterranean ,29 2,23, 20 c Ocean Active, silt rich 2, convergen (measured bathymetry over <10 km) Pacifi 1960s-vintage Mud to gravel; Washington, USA, Washington, c Ocean Active, to pebbles (measured bathymetry convergent SeaMARC II over <10 km) Pacifi 1980s-vintage Honshu, Japan, Presumably mud /yr** N/A§ 15 7.4 1 400 3 21 15 c Ocean Active, over 5 km) (measured bathymetry convergent Hydrosweep Pacifi SeaBeam and Mud to pebbles Hokkaido, Japan, /yr# 10 km 3 ,18 c Ocean 16 100-m Active, horizontal resolution) bathymetry convergent (better than Hydrosweep grained sand Central Chile, Pacifi Mud to coarse- 12 Yes Yes Yes Yes Yes No No TABLE 1. CHARACTERISTICS OF CANYON-AND-CHANNEL SYSTEMS 1. CHARACTERISTICS OF CANYON-AND-CHANNEL TABLE Active, convergent Venezuela, Venezuela, DEMs with a Caribbean Sea of 0.6% depth vertical accuracy 200-m-resolution 25 Yes; 17, driven gravity- ection data 3D seismic- Niger Delta, refl Atlantic Ocean les were compiled from published sources, which are highlighted in the row of references as emboldened and italicized numbers. les from high-resolution, multibeam bathymetric data sets that extend the continental shelf out to base of slope (Gar 25 58 76 250 200 110 200 200 170 270 285 16 40 N/A§ 3.2 km No No No No Yes No Yes Yes No† No Yes; driven size of Mexico gravity- Convex Convex Convex Convex Convex Convex Slightly concave Slightly concave Slightly concave Slightly concave Passive Passive ection data 3,4,17, 50 × 25 m) NW Gulf of 3D seismic- Exponential Linear Exponential Linear Linear Linear Linear Linear Linear Linear Mud to sand Mud to sand Mud to gravel refl (processed bin (1) East Breaks (2) Nigeria X A (3) Barbados Antonio (4) San Kushiro (5) Aoga (6) Astoria (7) (8) Rhone (9) Hudson (10) Mississippi ve longitudinal profi le uence We measured fi We tting function tting t/yr) latitude) ° 6 Note: System Geographic context Data Margin type Synsedimentary deformation References Glacial infl (>40 Longitudinal profi Fluvial sediment load (×10 across slope (km) Grain size the table. Normalized length Best-fi Divins and Metzger, 2009). The remaining profi 2009). Divins and Metzger,

Geosphere, April 2011 315 Covault et al. ncave ,29 4.8 11 c Ocean Active, Simrad Central 2, sand rich transform bathymetry Pacifi Mud to cobbles; California, USA, 19 Yes Yes c Ocean NOAA NOAA Active, Central sand rich transform likely small sheet NOS 1307N-11B bathymetric Unknown, but Pacifi Mud to cobbles; California, USA, ,29 8,11, — Sea Yes; Yes; 27 Mixed* France, common Sand rich earthquakes Mediterranean Qt terrace uplift, ) c Ocean USGS Active, (<3 arc- sand rich Southern transform resolution) bathymetry second grids; Pacifi 10-cm vertical Mud to gravel; NOAA/NGDC/ California, USA, continued 2000); (5) Butman et al. (2006); (6) Covault (2007); (7) Curray 0.4 0.5 1.3 c Ocean western Mediterranean Sea is a young, steep margin (post-Oligocene) with local USGS Active, (<3 arc- ) Huyghe et al. (2004); (13) Inman (2008); (14) and Jenkins (1999); (15) Klaus sand rich Southern transform resolution) bathymetry second grids; l. (1986); (20) Nelson (1970); (21) Noda et al. (2008); (22) Normark (23) Pacifi 10-cm vertical Mud to gravel; NOAA/NGDC/ California, USA, (28) Skene and Piper (2006); (29) Sømme et al. (2009). DEMs—digital elevation models; c Ocean USGS Active, (<3 arc- sand rich Southern transform resolution) likely small bathymetry second grids; Unknown, but Pacifi 10-cm vertical Mud to gravel; NOAA/NGDC/ California, USA, 2.2 c Ocean USGS Active, (<3 arc- sand rich Southern transform resolution) 6,10,13,22 6 6,10,14 10,14 littoral cell) bathymetry (Oceanside second grids; Pacifi 10-cm vertical Mud to gravel; NOAA/NGDC/ California, USA, 28 sand rich SeaBeam bathymetry 1980s-vintage Mud to gravel; Atlantic Ocean Eastern Canada, TABLE 1. CHARACTERISTICS OF CANYON-AND-CHANNEL SYSTEMS ( 1. CHARACTERISTICS OF CANYON-AND-CHANNEL TABLE 0) Graham and Bachman (1983); (11) Greene et al. (2002); (12 0) Graham and Bachman (1983); (11) uvial sediment load). ,25,29 2,17, No No Yes Yes Yes Yes 24 Ocean (~100-m mud rich horizontal SeaBeam resolution) bathymetry Brazil, Atlantic Mud to pebbles; ,29 2,9, 48 1200 4 NoNoYesNoNoNoNoYesNoNo 370380360542558818084140 Yes; 1 Linear Linear Logarithmic Logarithmic Logarithmic Logarithmic Logarithmic Logarithmic Logarithmic Linear Simrad Passive Passive Passive Mud rich (11) Zaire(11) Amazon (12) (13) Laurentian (14) La Jolla (15) Carlsbad (16) Oceanside (17) Newport (18) VarAscension (19) (20) Monterey resolution; resolution) bathymetry (better than West Africa, West 10-m vertical gravity-driven uvial sediment load). Atlantic Ocean Slightly concave Slightly concave concave Very concave Very concave Very concave Very concave Very concave Very concave Very Slightly co 100-m horizontal le uence References: (1) Babonneau et al. (2002); (2) Barnes and Normark (1985); (3) Beaubouef Friedmann (2000); (4) Booth ( tting function tting t/yr) latitude) 6 ° Hudson Canyon head is just south of 40° N latitude. These canyons head on the middle continental slope, rather than shelf edge. Rio Miapo discharge (not fl **Combined discharge of the Tokachi and Kushiro rivers (not fl Tokachi **Combined discharge of the Note: † § # *Mixed margins include settings adjacent to uplifting hinterland source areas (e.g., northwestern Mediterranean Sea). The north *Mixed margins include settings adjacent to uplifting hinterland source areas (e.g., northwestern Mediterranean Sea). (2003); (8) Fildani and Normark (2004); (9) Flood et al. (1991); (1 across slope (km) Grain size Longitudinal profi System (× 10 Normalized length Geographic context Fluvial sediment load (1991); (16) Laursen and Normark (2002); (17) Milliman Syvitski (1992); (18) et al. (1995); (19) Nagel a Taylor et al. (1985b); (24) Pirmez and Imran (2003); (25) (2000); (26) Pratson (1994); (27) Savoye (1993); Administration/National Geophysical Data Center; USGS—U.S. Geological Survey. Atmospheric NOAA/NGDC—National Oceanic and (>40 Glacial infl Data Synsedimentary deformation tectonism (Savoye et al., 1993). Margin type References Best-fi

316 Geosphere, April 2011 Canyon-and-channel longitudinal proﬁ les

1985; Adams and Schlager, 2000). For the Convex Profi les kaido and Honshu, respectively, are relatively visual analysis, profiles were grouped into large canyon–to–erosional-channel systems that convex-upward, slightly concave-upward, Six canyon-and-channel systems have con- deposited relatively coarse-grained sediment in and very concave-upward categories (Fig. 5). vex profi les, which are relatively fl at in their accretionary wedge-top and forearc basins, and Hereafter, convex and concave will be used for proximal reaches but are steeper in their distal transported sediment across the steep front of simplifi cation. reaches (East Breaks [1], Nigeria X [2], Bar- accretionary wedges that extend seaward into For the curve-fi tting analysis, we attempted to bados A [3], San Antonio [4], Kushiro [5], and trenches (Klaus and Taylor, 1991; Laursen and fi t profi les to three simple functions, exponen- Aoga [6]) (Fig. 6). Two of these profi les, East Normark, 2002; Noda et al., 2008) (Table 1 and tial, linear, and logarithmic, and we used coef- Breaks (1) and Barbados A (3), are best fi t, Fig. 6D). The Barbados A (3) system offshore fi cients of determination (r 2 values) from least- according to least-squares regression, to expo- Venezuela transported relatively coarse-grained squares regression to determine which function nential functions. The East Breaks (1) system is sediment across the Barbados Ridge Complex best describes a profi le (cf. Shepherd, 1985; commonly referred to as the Brazos-Trinity sys- (Huyghe et al., 2004) (Table 1). The system Adams and Schlager, 2000) (Fig. 2). Exponen- tem (e.g., Mallarino et al., 2006). Four profi les, originates on a tectonically quiescent segment tial functions are of the general form: Nigeria X (2), San Antonio (4), Kushiro (5), and of the continental slope, where the gradient is Aoga (6), are best fi t to linear functions (Fig. 2). fl atter, which facilitated the development of y = cebx, (1) These systems are from passive-margin slopes levee and overbank relief. Across more distal subjected to gravity-driven tectonic deforma- reaches, however, the system lacks levee relief where y is water depth, x is the down-system tion that produces diapirism, growth faults, and is incised into the steeper, actively uplifting distance, c and b are constants, and e is the base folds, and toe thrusts (e.g., the intraslope basin front of the Barbados Ridge Complex (Huyghe of the natural logarithm. Exponential functions province of the western Gulf of Mexico for East et al., 2004). indicate that profi les change basinward at an Breaks [1] and offshore the Niger Delta conti- increasing rate. Linear functions are of the gen- nental margin for Nigeria X [2]; Damuth, 1994; Slightly Concave Profi les eral form: Rowan et al., 2004) and tectonically active convergent margins (Barbados A [3], San Antonio Seven canyon-and-channel systems have y = mx + b, (2) [4], Kushiro [5], and Aoga [6]) (Table 1 and slightly concave profi les (Astoria [7], Rhone Fig. 6). All six of these systems were subjected [8], Hudson [9], Mississippi [10], Zaire [11], to synsedimentary tectonic deformation and Amazon [12], and Monterey [20]) (Fig. 7). All where m is the slope of the line of best fi t, and received relatively small volumes of sediment seven are best fi t to linear functions (Fig. 2). Five b is the intersection of the line with the y axis. over the last glacial cycle relative to large sub- of these systems (Rhone [8], Mississippi [10], Logarithmic functions are of the general form: marine fan systems that were provided volumi- Zaire [11], Amazon [12], and Monterey [20]) nous sediment in open ocean basins (discussed are associated with some of the largest deep-sea y = c ln x + b, (3) below in the Slightly Concave Profi les sec- fans in the world (Barnes and Normark, 1985) tion) (cf. fl uvial sediment-load measurements (Table 1 and Fig. 7). These generally mud-rich where c and b are constants, and ln is the natu- in Table 1). The development of depositional systems include enormous canyons that transi- ral logarithm. Logarithmic functions indicate architecture on passive margins deformed by tion to channels with well-developed levee and that profi les change quickly and then level out gravity-driven processes (East Breaks [1] and overbank relief and terminate as depositional basinward. They are the inverse of exponential Nigeria X [2]) corresponds with subtle gradient lobes in some cases greater than one thousand functions. changes across their diapiric and growth-faulted kilometers down-system (Fig. 7). The Monterey Simple visual analysis did not always cor- slopes (Pirmez et al., 2000) (Fig. 6C). Relatively (20) system is exceptional in that it developed respond with more objective curve fi tting. For fi ne-grained, shelf-edge, delta-fed sediment across the California transform margin, and, example, visual inspection of the Nigeria X (2), was transported through leveed channels of the similar to many of the sand-rich systems of the San Antonio (4), Kushiro (5), and Aoga (6) small East Breaks (1) and Nigeria X (2) slope margin, was active during the Holocene marine profi les indicates that they are convex (Fig. 5); channels to pockets of intraslope accommoda- transgression and highstand (Paull et al., 2005; however, they are objectively best fi t, accord- tion, where ponded turbidite systems devel- Fildani et al., 2006; Piper and Normark, 2009). ing to least-squares regression, to linear func- oped (Beaubouef and Friedmann, 2000; Booth One slightly concave system, Astoria (7), devel- tions, and, therefore, would be classifi ed as et al., 2000; Pirmez et al., 2000). In contrast, the oped across the Cascadia tectonically active linear profi les by the curve-fi tting method of San Antonio (4) system offshore Chile and the convergent margin offshore western North this study (Fig. 2). Kushiro (5) and Aoga (6) systems offshore Hok- America (Table 1).

Canyon-and-Channel Longitudinal Proﬁ les

Longitudinal profi les are presented below Figure 2 (on following fi ve pages). Plots of all canyon-and-channel longitudinal profi les. Left: according to groups determined from visual Lengths of entire profi les. Arrows indicate bases of continental slopes or ends of confi ned inspection (Fig. 5). Information pertain- reaches of canyon-and-channel systems used for normalization. Bases of slopes were not ing to best-fi tting functions of profi les is also measured at arbitrary or unit lengths, but were defi ned at the points where profi les reached provided, as well as continental-margin and gradients <0.25° and curvatures (i.e., down-system change in gradient) between –10–7 and depositional-architecture context. Table 1 pro- 10–7. Notice distal reaches of only a few profi les were cut off by this normalization procedure vides more information pertaining to the char- (i.e., Mississippi [10], Zaire [11], and Amazon [12]). Right: Normalized profi les across con- acteristics of canyon-and-channel systems and tinental slopes with best-fi tting curves and functions according to least-squares regression continental margins. (red lines).

Geosphere, April 2011 317 Covault et al.

DOWN-SYSTEM LENGTH (m) DOWN-SYSTEM LENGTH (m) 0 10000 20000 30000 40000 50000 60000 70000 0 10000 20000 30000 40000 50000 60000 70000 0 0

200 200 400 400 (1) East Breaks (1) East Breaks 600 600 800 800 1000 1000 Intraslope 1200 end of system y = 436.29e2E-05x 1200 1400 R² = 0.9832 Exponential

1400 WATER DEPTH (m) WATER DEPTH (m) 1600 Normalized length 1600 (see right column) 1800 DOWN-SYSTEM LENGTH (m) DOWN-SYSTEM LENGTH (m) 0 20000 40000 60000 80000 0 20000 40000 60000 80000 0 0 200 200 400 (2) Nigeria X 400 (2) Nigeria X 600 600 800 800 1000 1000 1200 Intraslope 1200 1400 end of system 1400 1600 1600 y = 0.0185x + 386.95 WATER DEPTH (m) WATER DEPTH (m) 1800 1800 R² = 0.9949 Normalized length Linear 2000 (see right column) 2000 DOWN-SYSTEM LENGTH (m) DOWN-SYSTEM LENGTH (m) 0 50000 100000 150000 200000 250000 300000 0 50000 100000 150000 200000 250000 300000 0 0

500 500

1000 (3) Barbados A 1000 (3) Barbados A

1500 1500

2000 2000 Base of slope and 2500 end of system 2500 y = 1478.4e3E-06x 3000 3000 R² = 0.9874 3500 Exponential

WATER DEPTH (m) 3500 WATER DEPTH (m) Normalized length 4000 (see right column) 4000 DOWN-SYSTEM LENGTH (m) DOWN-SYSTEM LENGTH (m) 0 20000 40000 60000 80000 100000 120000 0 20000 40000 60000 80000 100000 120000 0 0 1000 (4) San Antonio 1000 (4) San Antonio 2000 2000

3000 Base of slope and 3000 end of system 4000 4000 y = 0.0417x + 316.96 R² = 0.9753 5000 Normalized length 5000 Linear WATER DEPTH (m) WATER DEPTH (m) (see right column) 6000 6000

Figure 2.

318 Geosphere, April 2011 Canyon-and-channel longitudinal proﬁ les

DOWN-SYSTEM LENGTH (m) DOWN-SYSTEM LENGTH (m) 0 50000 100000 150000 200000 250000 0 50000 100000 150000 200000 250000 0 0

1000 1000 (5) Kushiro (5) Kushiro 2000 2000

3000 3000

4000 Base of slope and 4000 end of system 5000 5000 y = 0.03x - 34.786 6000 6000 R² = 0.9833 WATER DEPTH (m) WATER DEPTH (m) Linear Normalized length 7000 (see right column) 7000 DOWN-SYSTEM LENGTH (m) DOWN-SYSTEM LENGTH (m) 0 50000 100000 150000 200000 250000 0 50000 100000 150000 200000 250000 0 0

1000 1000 (6) Aoga (6) Aoga 2000 2000

3000 3000

4000 Base of slope and 4000 end of system 5000 5000 y = 0.0273x + 711.33 6000 6000 R² = 0.9818 WATER DEPTH (m) WATER DEPTH (m) Normalized length Linear 7000 (see right column) 7000 DOWN-SYSTEM LENGTH (m) DOWN-SYSTEM LENGTH (m) 0 50000 100000 150000 200000 250000 300000 0 50000 100000 150000 200000 250000 0 0

500 500 (7) Astoria (7) Astoria 1000 1000

1500 1500

2000 Base of slope 2000

2500 2500 y = 0.013x + 463.34 3000 Normalized length 3000 R² = 0.9593 WATER DEPTH (m) (see right column) WATER DEPTH (m) Linear 3500 3500 DOWN-SYSTEM LENGTH (m) DOWN-SYSTEM LENGTH (m) 0 50000 100000 150000 200000 0 50000 100000 150000 200000 0 0

500 500 (8) Rhone (8) Rhone 1000 1000 1500 1500 Base of slope and end of system 2000 y = 0.0106x + 601.82 2000 R² = 0.9259 2500 Linear WATER DEPTH (m) WATER DEPTH (m) Normalized length 2500 (see right column) 3000

Figure 2 (continued).

Geosphere, April 2011 319 Covault et al.

DOWN-SYSTEM LENGTH (m) DOWN-SYSTEM LENGTH (m) 0 100000 200000 300000 0 100000 200000 300000 0 0 500 500 1000 (9) Hudson 1000 (9) Hudson 1500 1500 2000 2000 2500 2500 Base of slope 3000 3000 3500 y = 0.0134x + 785.12 3500 4000 R² = 0.9238 WATER DEPTH (m) WATER DEPTH (m) Normalized length Linear 4000 (see right column) 4500 DOWN-SYSTEM LENGTH (m) DOWN-SYSTEM LENGTH (m) 0 100000 200000 300000 400000 0 100000 200000 300000 0 0 500 (10) Mississippi 500 (10) Mississippi 1000 1000 1500 1500

Base of slope 2000 2000 2500 y = 0.0086x + 317.93 R² = 0.9925 2500 Linear WATER DEPTH (m) Normalized length WATER DEPTH (m) 3000 (see right column) 3000 DOWN-SYSTEM LENGTH (m) DOWN-SYSTEM LENGTH (m) 0 200000 600000 1000000 0 100000 200000 300000 0 0

1000 (11) Zaire 500 (11) Zaire Base of slope 1000 2000 1500 3000 Normalized length End of system 2000 (see right column) 4000 y = 0.0072x + 353.51 2500 R² = 0.9718 WATER DEPTH (m) WATER DEPTH (m) Linear 5000 3000

6000 3500 DOWN-SYSTEM LENGTH (m) DOWN-SYSTEM LENGTH (m) 0 200000 400000 600000 800000 1000000 0 100000 200000 300000 400000 500000 0 0

500 500 (12) Amazon (12) Amazon 1000 1000 1500 1500 2000 Base of slope 2000 2500 2500 3000 End of system 3000 3500 y = 0.0081x + 600.98 WATER DEPTH (m) Normalized length WATER DEPTH (m) R² = 0.9773 4000 (see right column) 3500 Linear 4000 Figure 2 (continued).

320 Geosphere, April 2011 Canyon-and-channel longitudinal proﬁ les

DOWN-SYSTEM LENGTH (m) DOWN-SYSTEM LENGTH (m) 0 100000 200000 300000 400000 0 100000 200000 300000 400000 0 0 500 500 1000 1000 (13) Laurentian 1500 (13) Laurentian 1500 2000 2000 2500 2500 y = 888ln(x) - 6658.9 3000 R² = 0.9229 3000 3500 Base of slope Logarithmic 3500 4000 4000 4500 WATER DEPTH (m) WATER DEPTH (m) 5000 4500 Normalized length 5000 (see right column) DOWN-SYSTEM LENGTH (m) DOWN-SYSTEM LENGTH (m) 0 10000 20000 30000 40000 50000 60000 0 10000 20000 30000 40000 50000 60000 0 0 200 (14) La Jolla 200 (14) La Jolla 400 400 y = 284.55ln(x) - 2084.9 600 600 R² = 0.9643 Logarithmic End of system 800 800 1000 1000 WATER DEPTH (m) Normalized length WATER DEPTH (m) 1200 (see right column) 1200 DOWN-SYSTEM LENGTH (m) DOWN-SYSTEM LENGTH (m) 0 5000 10000 15000 20000 25000 30000 0 5000 10000 15000 20000 25000 0 0

100 100

200 (15) Carlsbad 200 (15) Carlsbad 300 300 400 y = 216.98ln(x) - 1500.2 400 R² = 0.9901 500 Logarithmic 500 End of system 600 600 700 700 WATER DEPTH (m) Normalized length WATER DEPTH (m) 800 (see right column) 800 DOWN-SYSTEM LENGTH (m) DOWN-SYSTEM LENGTH (m) 0 20000 40000 60000 0 20000 40000 60000 0 0 200 (16) Oceanside 200 (16) Oceanside 400 400 y = 270.8ln(x) - 1914.6 R² = 0.9844 600 600 Logarithmic End of system 800 800

1000 1000 WATER DEPTH (m) Normalized length WATER DEPTH (m) (see right column) 1200 1200

Figure 2 (continued).

Geosphere, April 2011 321 Covault et al.

DOWN-SYSTEM LENGTH (m) DOWN-SYSTEM LENGTH (m) 0 20000 40000 60000 80000 100000 120000 0 20000 40000 60000 80000 100000 0 0 200 (17) Newport 200 (17) Newport 400 400 y = 206.05ln(x) - 1419.2 600 600 R² = 0.9897 Base of slope Logarithmic 800 End of system 800

1000 1000 WATER DEPTH (m) Normalized length WATER DEPTH (m) 1200 (see right column) 1200 DOWN-SYSTEM LENGTH (m) DOWN-SYSTEM LENGTH (m) 0 50000 100000 150000 0 20000 40000 60000 80000 100000 0 0 500 (18) Var 500 (18) Var 1000 1000 y = 515.19ln(x) - 3454.6 1500 1500 R² = 0.9743 Base of slope Logarithmic End of system 2000 2000

2500 2500 WATER DEPTH (m) WATER DEPTH (m) Normalized length (see right column) 3000 3000 DOWN-SYSTEM LENGTH (m) DOWN-SYSTEM LENGTH (m) 0 20000 40000 60000 80000 100000 0 20000 40000 60000 80000 100000 0 0

500 500 (19) Ascension (19) Ascension 1000 1000

1500 1500 y = 750.06ln(x) - 5543.3 2000 End of system 2000 R² = 0.9847 Logarithmic 2500 2500

3000 Normalized length WATER DEPTH (m) WATER DEPTH (m) 3000 (see right column) 3500 DOWN-SYSTEM LENGTH (m) DOWN-SYSTEM LENGTH (m) 0 50000 100000 150000 0 50000 100000 150000 0 0

500 500 (20) Monterey (20) Monterey 1000 1000 1500 1500 2000 2000 2500 2500 y = 0.0248x + 365.41 Base of slope 3000 R² = 0.9452 WATER DEPTH (m) WATER DEPTH (m) 3000 3500 Linear Normalized length 3500 (see right column) 4000

Figure 2 (continued).

322 Geosphere, April 2011 Canyon-and-channel longitudinal proﬁ les

DOWN-SYSTEM LENGTH (m) context of their relative contributions to longitudinal-profi le shapes in the convex, slightly 0 400000 800000 1200000 concave, and very concave profi le groups. 0 There are only three canyon-and-channel sys- 15 16 (1) East Breaks (8) Rhone (15) Carlsbad tems whose longitudinal-profi le shapes do not 14 17 (2) Nigeria X (9) Hudson (16) Oceanside correspond well with continental-margin types 1000 1 (3) Barbados A (10) Mississippi (17) Newport or depositional architectures characteristic of 2 (4) SanAntonio (11) Zaire (18) Var other systems in their common profi le group. 2000 8 (5) Kushiro (12) Amazon (19) Ascension These are the Astoria (7), Laurentian (13), and 10 (6) Aoga (13) Laurentian (20) Monterey Monterey (20) systems, which are discussed (7) Astoria (14) La Jolla below in the Exceptional Canyon-and-Channel 3000 18 Systems section. 19 7 3 Convex profi les appear to have developed as a result of the dominance of seafl oor uplift and 20 9 4000 deformation (e.g., East Breaks [1], Nigeria X [2]; 11 Barbados A [3], San Antonio [4], Kushiro [5], 13 12

WATER DEPTH (m) 5000 and Aoga [6]) (Fig. 9). Such profi les developed in passive margins affected by gravity-driven 4 tectonics and tectonically active convergent 5 6000 margins. Even though the signature of seafl oor 6 uplift and deformation is apparent in the convex shape of these profi les, other factors, such as 7000 erosion by sediment gravity fl ows, could have impacted seafl oor morphology. Contraction Figure 3. Canyon-and-channel longitudinal profi les. above detachment surfaces in both types of belts can result in a broad zone of uplift and deformation, which is manifested in the evolving Very Concave Profi les and, similar to the Astoria (7) system dis- wedge shape of fold-and-thrust belts (Dahlen cussed above, was fed relatively large volumes et al., 1984; Rowan et al., 2004). This evolv- Seven canyon-and-channel systems have of coarse-grained sediment during subglacial ing wedge shape maintains an approximately very concave profi les (Laurentian [13], La Jolla transitions (Skene and Piper, 2006; Piper et al., convex regional profi le, which is also refl ected [14], Carlsbad [15], Oceanside [16], Newport 2007; Piper and Normark, 2009) (Table 1). The by canyon-and-channel longitudinal profi les [17], Var [18], and Ascension [19]), which Laurentian (13) conduit is remarkable for its (Fig. 9). In unstable progradational, or supply- are relatively steep in their proximal reaches straightness, 25-km width, residual buttes, fl at dominated (Carvajal et al., 2009), passive- but are fl at in their distal reaches (Fig. 8). All erosional fl oor, and spillover channels (Piper margin slope settings, gravitational instabilities seven profi les are best fi t to logarithmic func- and Normark, 2009). can facilitate gravity-driven diapirism, growth tions (Fig. 2). Six of these systems are rich in faulting, and fold-and-thrust–related uplift and sand and developed across the California and Development of Longitudinal Profi les deformation (e.g., the western Gulf of Mexico French Mediterranean margins. These margins and Their Relationships to Continental for East Breaks [1] and offshore west Africa are characterized by relatively steep slopes out- Margin Types and Depositional Styles for Nigeria X [2]; Hedberg, 1970; Winker and board of narrow shelves and nearby hinterlands Edwards, 1983; Rowan et al., 2004). In con- from which relatively coarse-grained sediment Because we examined canyon-and-channel vergent margins, tectonic processes including is shed (La Jolla [14], Carlsbad [15], Ocean- systems on the modern seafl oor, they refl ect basin-localized subsidence, fault-supported side [16], Newport [17], Var [18], and Ascen- processes and forcings that operated since the inner and outer margin uplift (e.g., Melnick sion [19]) (Table 1 and Fig. 8). Five of these last glacial cycle (e.g., <100 ka; Lambeck and et al., 2006; Collot et al., 2008), and construc- systems, La Jolla (14), Carlsbad (15), Ocean- Chappell, 2001). However, effects of the more tion of a frontal prism of accreted sediment side (16), Newport (17), and Var (18), have distant past—for example, millions of years of (Dahlen et al., 1984; Rowan et al., 2004) can canyons that transition to channels with modest sedimentary-basin fi lling or uplift of an accre- steepen the lower slope and work in concert with levee and overbank relief and terminate as tionary wedge—also had a profound infl uence deep-sea canyon–and–channel-related sedimen- depositional lobes. The Ascension (19) system on some of these recently developed sediment- tary processes to produce the characteristic con- offshore central California also exhibits a well- delivery systems by establishing the seafl oor vex expression of longitudinal profi les (Ranero developed canyon-and-channel system that template and morphology across which canyons et al., 2006; von Huene et al., 2009). In particu- does not terminate as depositional lobes; rather, and channels developed. The groups of normal- lar, time-transgressive landward migration of it is a signifi cant tributary to the Monterey (20) ized canyon-and-channel longitudinal profi les the trench (e.g., Soh and Tokuyama, 2002; Noda system (Normark et al., 1985c; Nagel et al., of this study generally refl ect varying degrees of et al., 2008), consequent margin steepening, and 1986; Greene et al., 2002; Fildani and Normark, seafl oor uplift and deformation, construction of truncation of the submerged forearc caused by 2004). The six aforementioned systems were depositional relief, and degradation of the sea- frontal subduction erosion can be fundamentally subjected to synsedimentary tectonic defor- fl oor by erosion associated with sediment grav- important to longitudinal profi le development in mation; however, the Laurentian (13) system ity fl ows and other mass movements (Fig. 9). convergent margins (Ranero et al., 2006; von developed across the Atlantic passive margin These infl uences are explained below in the Huene et al., 2009).

Geosphere, April 2011 323 Covault et al.

NORMALIZED DOWN-SYSTEM LENGTH proximal reach of mature passive-margin lon- A gitudinal profi les relative to profi les from the 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 immature, underfi lled margin offshore southern 0.0 California characterized by steeper slopes and 1 (1) East Breaks (8) Rhone narrower shelves (Fig. 4B). Thus, progradation 0.1 (2) Nigeria X (11) Zaire of these sediment supply–dominated passive (3) Barbados A (12) Amazon margins associated with slope clinothem and fan 0.2 (4) SanAntonio (14) La Jolla accretion favors the development of a relatively 3 (5) Kushiro (15) Carlsbad convex seafl oor across which channels subse- 0.3 6 (6) Aoga (16) Oceanside quently incise and create a slightly concave profi le shape (cf. Carvajal et al., 2009; Gerber et al., TH 8 (17) Newport 0.4 4 (19) Ascension 2009; Ryan et al., 2009a). 5 Very concave profi les predominantly devel- 0.5 Relatively convex profiles oped on immature, or erosional (Ryan et al., 12 2009a), continental margins, some of which 11 are dominated by strike-slip deformation (e.g., 0.6 La Jolla [14], Carlsbad [15], Oceanside [16], 17 15 Newport [17], Var [18], and Ascension [19]) NORMALIZED DEP 0.7 19 14 2 (Fig. 9). In such settings, deformation contrib- utes to steep slopes outboard of narrow shelves 0.8 (cf. erosional margins of Ryan et al., 2009a). The narrow shelves offshore California and the Relatively concave profiles 0.9 French Riviera and nearby hinterlands suggest 16 that relatively coarse-grained sediment is contin- 1.0 uously fed to canyon-and-channel systems during both high and low stands of sea level (Savoye et al., 1993; Covault et al., 2007). Gerber et al. B NORMALIZED DOWN-SYSTEM LENGTH NORMALIZED DOWN-SYSTEM LENGTH (2009) demonstrated the infl uence of erosion 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.0 by sediment gravity fl ows across steep slopes of (8) Rhone (8) Rhone the Catalan margin in the Mediterranean Sea on (11) Zaire (11) Zaire 0.2 (12) Amazon 0.2 (12) Amazon the development longitudinal-profi le concavity. (14) La Jolla H (14) La Jolla Because the degree of degradation is related to (15) Carlsbad (15) Carlsbad EPTH the cumulative shear stress imposed by a number D 0.4 8 (16) Oceanside 0.4 (16) Oceanside (17) Newport (17) Newport of sediment gravity fl ows on the seafl oor (Mid- 12 (19) Ascension (19) Ascension dleton and Southard, 1984; Leeder, 1999; Boggs, 0.6 0.6 2001), relatively coarse grain sizes, more con- 17 15 11 14 tinuous erosion by sediment gravity fl ows, and

NORMALIZED 0.8 19 NORMALIZED DEPT 0.8 steep slopes inherent to these immature margins promoted more signiﬁ cant seaﬂ oor degradation 16 than in other settings (cf. Gerber et al., 2009). 1.0 1.0

Figure 4. Canyon-and-channel longitudinal-profi le normalization on the basis of pro- Exceptional Canyon-and-Channel Systems fi le length from canyon head to the end of the confi ned portion of the system (e.g., at the channel-to-lobe transition zone). (A) Only 14 profi les include the entire confi ned segments of There are a couple of exceptional canyon-and- their canyon-and-channel systems. (B) Closer inspection of relatively concave profi les shows channel systems documented in this study that that some profi les are distinctively more convex in their proximal reaches (dashed black exhibit more concave profi les than one might box; <0.4 of their total down-system length) relative to other profi les. predict on the basis of their continental-margin setting: the Astoria (7) and Laurentian (13) systems (Figs. 7, 8, and 10). Both are relatively high-latitude systems and, as a result, were par- Slightly concave profi les are commonly asso- progradational, or supply-dominated margins, ticularly sensitive to climatic variability associated with mature passive continental margins which have thick sedimentary prisms composed ciated with the latest Pleistocene-to-Holocene not subjected to appreciable tectonic uplift, but of well-developed clinothem and fan sequences glacial-to-interglacial transition (Table 1 and gradual subsidence as a result of thermal cool- (Hedberg, 1970; Ross et al., 1994; Carvajal Fig. 10). The slightly concave, rather than the ing of the lithosphere (e.g., Rhone [8], Hudson et al., 2009; Gerber et al., 2009; Ryan et al., expected convex, profi le of the Astoria (7) sys- [9], Mississippi [10], Zaire [11], and Amazon 2009a). Such preexisting depositional archi- tem might have resulted from the margin receiv- [12]) (Fig. 9). However, they can have pro- tecture establishes a relatively convex seafl oor ing pulses of coarse-grained sediment and water nounced relief as a result of preexisting deposi- template across which canyons and channels from periodic catastrophic fl oods of the Colum- tional architecture. This preexisting depositional extend. This seafl oor template facilitates the bia River since the Last Glacial Maximum architecture is characteristic of constructional, development of a distinctively less concave (Nelson et al., 1970; Piper and Normark, 2009).

324 Geosphere, April 2011 Canyon-and-channel longitudinal proﬁ les

NORMALIZED ACROSS-SLOPE LENGTH A similar situation exists for the Laurentian (13) A system, which exhibits a very concave profi le, 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 even though it developed across the Atlantic 0.0 passive margin (Table 1; Figs. 8 and 10B). For 1 (1) East Breaks (8) Rhone both high-latitude systems, numerous sandy and (2) Nigeria X (9) Hudson 0.1 coarser-grained, thick mass movements initiated (3) Barbados A (10) Mississippi during glacial-to-interglacial transitions, which (4) SanAntonio (11) Zaire 0.2 promoted seafl oor erosion and the develop- 3 (5) Kushiro (12) Amazon (6) Aoga (13) Laurentian ment of relatively concave longitudinal profi les 0.3 6 (7) Astoria (14) La Jolla (Skene and Piper, 2006; Piper et al., 2007; Piper 9 and Normark, 2009). 8 0.4 (15) Carlsbad The Monterey (20) system is unique rela- 12 5 (16) Oceanside tive to other slightly concave profi les in that it (17) Newport is sand rich and developed across the California 0.5 13 11 4 (18) Var transform margin (Table 1 and Fig. 7). However, 7 (19) Ascension the Monterey (20) system feeds a large deep- 0.6 17 15 10 (20) Monterey sea fan (Fildani and Normark, 2004). Volumi- 2 nous preexisting fan deposits likely fostered a 0.7 14 relatively convex proximal segment of the Mon- NORMALIZED DEPTH terey (20) profi le, and turbidite deposition was 0.8 LENGTH (km) recently focused in the proximal reaches of the 0 400 800 canyon (Paull et al., 2005) (Figs. 2 and 7). The 0 0.9 19 distal reaches of the profi le are more steeply 2 16 concave, which is common in strike-slip settings. Gerber et al. (2009) related such a convex- 1.0 20 4 18 to-concave longitudinal-profi le shape across the 6 Ebro margin in the Mediterranean Sea to sedi-

WATER DEPTH (km) ment–gravity-fl ow deposition in a prograding canyon. Similarly, the Monterey (20) profi le B NORMALIZED ACROSS-SLOPE LENGTH shows that the seafl oor might be raised as a 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 result of very recent localized deposition (i.e., 0.0 during the Holocene, <10 ka; Lambeck and Chappell, 2001; Paull et al., 2005; Fildani et al., Convex profiles 0.1 2006). These observations suggest that canyons Slightly concave profiles and channels are not merely conduits for sediment transport, but can be sites of deposition 0.2 Very concave profiles that might be detectable from profi le analysis. Tectonic circumstances have also been inter- 0.3 preted to govern Monterey (20) profi le morphology (Greene et al., 2002). Monterey Bay 0.4 of the central California continental margin includes two contrasting physiographic and 0.5 tectonic provinces separated by the Palo Colo- rado–San Gregorio fault zone: (1) the eastern 0.6 Salinian Block comprises metamorphic and granitic plutonic rocks; and (2) the western San 0.7 Simeon Block comprises Franciscan volcanic,

NORMALIZED DEPTH metamorphic, and sedimentary rocks (Mullins and Nagel, 1981; Greene et al., 2002). The Palo 0.8 Colorado–San Gregorio fault zone crosses the axis of Monterey (20) Canyon at ~2000-m water 0.9 depth, which approximately coincides with the infl ection point between relatively convex and 1.0 concave segments of the canyon-and-channel system (Paull et al., 2005) (Fig. 2). Greene et al. Figure 5. (A) All canyon-and-channel longitudinal profi les normalized across their conti- (2002) noted different Monterey (20) Canyon nental slopes. Bases of slopes were not measured at arbitrary or unit lengths; they were morphologies across the fault zone: the eastern –7 defi ned at the points where profi les reached gradients <0.25° and curvatures between –10 Salinian Block displays steeper, V-shaped can- –7 and 10 . Inset: Full-length profi les from Figure 3. (B) Profi le groups based on relative con- yon cross-sectional morphology; the western vexity or concavity from visual inspection. San Simeon Block displays broader, U-shaped

Geosphere, April 2011 325 Covault et al.

A DOWN-SYSTEM LENGTH (m) C United States Gulf Coast 0 400000 800000 1200000 0 30°N (1) East Breaks Passive-margin slopes with Mississippi Canyon (2) Nigeria X gravity-driven diapirism and 1000 East Breaks 2 fold-and-thrust deformation canyon-and-channel 2000 1 system 0 400000 800000 1200000 0 (3) Barbados A (4) SanAntonio 1000 Tectonically active (5) Kushiro convergent margins (6) Aoga 2000

3000 25°N WATER DEPTH (m) 6 3 –2000 m 4000 5 –1000 m 4 0 80 160 MILES –3000 m 5000 0 80 160 KILOMETERS 6000 95°W90°W 85°W 7000 NORMALIZED DOWN-SYSTEM LENGTH B D Hokkaido, Japan 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 0.0 Kushiro m 1 (1) East Breaks –1000 0.1 (2) Nigeria X Canyon-and-channel –2000 m (3) Barbados A system 0.2 (4) SanAntonio –3000 m (5) Kushiro 0.3 (6) Aoga –4000 m m –5000 42°N 0.4 3 –6000–7000 m m 5 0.5 4 Convex profiles 0.6

0.7 2 6

NORMALIZED DEPTH 0.8 0 30 60 MILES

0.9 03060KILOMETERS

1.0 142°E 144°E 146°E 148°E

Figure 6. Convex longitudinal profi les. (A) Profi les before normalization. (B) Profi les normalized across their continental slopes. (C) Example bathymetry from the Gulf of Mexico passive margin dominated by diapirism and gravity-driven, fold-and-thrust-related tectonic deformation. Contour interval is –1000 m. East Breaks (1) system is yellow (Pirmez et al., 2000). Bathymetry from GeoMapApp, http://www.geomapapp.org (Ryan et al., 2009b). (D) Example bathymetry from the Tokachi-oki forearc basin and accretionary wedge offshore Hokkaido, Japan. Contour interval is –1000 m. Kushiro (5) system is yellow (Noda et al., 2008). Bathymetry from GeoMapApp, http://www.geomapapp.org (Ryan et al., 2009b). morphology. Paull et al. (2005) also noted that Schlager, 2000). Profi les that were grouped Rhone (8), Hudson (9), Mississippi (10), Zaire bends in the upper Monterey (20) Canyon are based on visual inspection generally correspond (11), and Amazon (12) profi les (Fig. 2). The oriented parallel to regional structures, presum- with continental-margin type and depositional Nigeria X (2), San Antonio (4), Kushiro (5), and ably as a result of differential erosion along architecture, with a few exceptions. More objec- Aoga (6) systems developed in the Niger Delta fault-generated weaknesses (Greene, 1990). tive curve-fi tting methods do an adequate job passive margin affected by gravity-driven tec- of differentiating the most convex and concave tonics and tectonically active convergent mar- Methods of Grouping Longitudinal Profi les profi les; however, there is more ambiguity asso- gins, and contributed to distinctively different ciated with differentiating between less convex depositional architectures relative to the Rhone We employed two methods in order to group and slightly concave profi les (Fig. 2). For exam- (8), Hudson (9), Mississippi (10), Zaire (11), longitudinal profi les: (1) visual inspection and ple, visual inspection of the Nigeria X (2), San and Amazon (12) systems. categorization on the basis of relative convexity Antonio (4), Kushiro (5), and Aoga (6) profi les More objective numerical methods, however, or concavity; and (2) more objective categori- indicates that they are convex (Fig. 5); however, have been shown to adequately differentiate zation on the basis of best-fi tting mathemati- they are objectively best fi t to linear functions submarine geomorphic features. Adams and cal functions (cf. Shepherd, 1985; Adams and and, therefore, are linear profi les along with the Schlager (2000) grouped 19 passive continental-

326 Geosphere, April 2011 Canyon-and-channel longitudinal proﬁ les

A –4000 m

–3000 m

–2000 m 5°N –1000 m Amazon Canyon-and-channel system

Brazil

0° 0 100 200 MILES

0 100 200 KILOMETERS

55°W 50°W 45°W B DOWN-SYSTEM LENGTH (m) 0 400000 800000 1200000 0 (8) Rhone (9) Hudson 1000 (10) Mississippi Mature passive margins (11) Zaire 8 2000 (12) Amazon 10

3000 7 9 20 4000 11 12 5000 (7) Astoria (20) Monterey Exceptional systems

WATER DEPTH (m) 6000

7000 C NORMALIZED DOWN-SYSTEM LENGTH (Normalized from canyon head to end of channel) (Normalized across slope)

0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.0 (8) Rhone (7) Astoria (11) Zaire (8) Rhone 0.2 8 (12) Amazon 0.2 (9) Hudson (10) Mississippi 0.4 0.4 (11) Zaire 10 12 (12) Amazon (20) Monterey 0.6 0.6 9 12 7 8 11 0.8 0.8 20 11 Slightly concave profiles Slightly concave profiles NORMALIZED DEPTH 1.0 NORMALIZED DEPTH 1.0

Figure 7. Slightly concave longitudinal profiles. (A) Example bathymetry from the Amazon deep-sea fan (GeoMapApp, http:// www.geomapapp.org; Ryan et al., 2009b). Contour interval is –1000 m. Amazon (12) system is yellow (Pirmez and Imran, 2003). (B) Profi les before normalization. (C) Left: Profi les normalized from canyon heads to ends of channels. Right: Profi les normalized across their continental slopes.

Geosphere, April 2011 327 Covault et al.

A -1000 m

-2000 m 44°N

France

Var Canyon-and-channel system 43°N

0 30 60 MILES

03060KILOMETERS

6°E 7°E 8°E 9°E 10°E B Southern California 0 10 20 MILES 01020KILOMETERS -100 m

-500 m Figure 8. Very concave longitudinal profi les. (A) Example bathymetry from the Mediterranean Sea (GeoMapApp, http://www.geomapapp.org; Ryan et al., 2009b). Con- tour interval is –1000 m. Var (18) system is yellow Newport systemm (Savoye et al., 1993). Notice proximity to Alpine sediment source area, narrow shelf, and steep slope. (B) Example bathymetry from offshore southern California (Gardner and Dartnell, 2002; Divins and Metzger, 2009). Contour anside system e Carlsbad system interval is –100 m. Carlsbad (15), Oceanside (16), and Oceanside system Newport (17) systems are yellow (Graham and Bachman, 33°N 1983; Covault et al., 2007; Covault et al., 2010). (C) Pro- 118°W 117°W fi les before normalization. (D) Left: Profi les normalized C DOWN-SYSTEM LENGTH (m) from canyon heads to ends of channels. Right: Profi les 0 400000 800000 1200000 normalized across their continental slopes. 0 15 (14) La Jolla (15) Carlsbad 16 Young margins with 1000 (16) Oceanside steep slopes and 17 (17) Newport 16 narrow shelves 2000 (18) Var (19) Ascension

3000 18 19 (13)Laurentian Exceptional system 4000 13 WATER DEPTH (m) D NORMALIZED DOWN-SYSTEM LENGTH (Normalized from canyon head to end of channel) (Normalized across slope)

0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.0 (14) La Jolla (13) Laurentian

(15) Carlsbad PTH (14) La Jolla 0.2 (16) Oceanside 0.2 (15) Carlsbad (17) Newport (16) Oceanside 0.4 0.4 (17) Newport (18) Var 14 (19) Ascension 0.6 0.6 17 15 14 16 15 0.8 0.8 19 16 17 Very concave profiles Very concave 18 NORMALIZED DE NORMALIZED DEPTH 1.0 1.0 profiles 13

328 Geosphere, April 2011 Canyon-and-channel longitudinal proﬁ les

Dominant control Long-profile shape Margin profile and architecture

NORMALIZED ACROSS-SLOPE LENGTH Slightly concave 0.0 1.0 Appreciable pre-existing depositional relief associated with mature Preexisting 0.0 margins

depositional Slightly concave Extensive leveed channel relief Preexisting fan deposits NORMALIZED DEPTH 1.0

NORMALIZED ACROSS-SLOPE LENGTH Convex 0.0 1.0 Tectonic uplift and deformation in passive-margin gravity-driven Tectonic uplift 0.0 and convergent margins

and deformation Convex Turbidites in pockets of accommodation NORMALIZED DEPTH 1.0

NORMALIZED ACROSS-SLOPE LENGTH Very concave 0.0 1.0 Enhanced sediment-gravity-flow erosion associated with young, Erosional 0.0 underfilled margins with steep slopes and close proximity to source areas sedimentary Very concave processes Narrow shelf Sediment gravity flow accelerating down the steep slope Nearby Coarse-grained hinterland fan NORMALIZED DEPTH 1.0

Figure 9. Summary chart of controls on longitudinal-profi le shape: preexisting depositional relief, tectonic uplift and deformation, and erosional sedimentary processes. Although profi les refl ect varying degrees of controlling factors, and exceptional profi les exist, profi le groups are located adjacent to dominant controls and general continental-margin types with characteristic depositional architectures. Average profi les for each group are represented by bold black lines.

margin profi les on the basis of three functions: low a Gaussian curve as a result of perturbing and predictive groups relative to similar meth- linear, exponential, and Gaussian distribution. extrinsic processes at the shelf edge (e.g., wave- ods applied to canyon-and-channel longitudi- Linear functions describe unstable margins reworking processes and shelf-edge instabili- nal profi les of this study? Adams and Schlager that are interpreted by Adams and Schlager ties; Adams and Schlager, 2000). Quantitative (2000) only examined passive continental (2000) to rest at the angle of repose. Exponen- characteristics of margins are effective at pre- margins in order to avoid tectonic infl uences tial functions represent the exponential decay of dicting depositional architecture and sediment on primary depositional setting (Pratson and sediment transport capacity or competence with caliber (Adams and Schlager, 2000). Why were Haxby, 1996). If we were to exclude canyons increasing distance across a margin (Adams and objective curve-fi tting methods of entire-margin and channels of tectonically active continental Schlager, 2000). The majority of margins fol- profi les more effective at creating meaningful margins from our analysis, profi les would be

Geosphere, April 2011 329 Covault et al.

neatly differentiated into two groups: (1) linear profi les across mature margins with large depositional fans (e.g., Rhone [8], Hudson [9], Mis- 0 200 400 MILES sissippi [10], Zaire [11], and Amazon [12]); and A (2) logarithmic profi les across settings domi- 0 200 400 KILOMETERS nated by erosional sedimentary processes (e.g., Laurentian [13] and Var [18]). Visual inspection of longitudinal profi les, 50°N therefore, is relatively useful in differentiating profi les into groups with some predic- Astoria Western tive capability of continental-margin type and Canyon-and-channel North America depositional architecture; however, exceptional system Columbia River longitudinal profi les dominated by erosional drainage basin sedimentary processes (e.g., Astoria [7] and Laurentian [13]) show the shortcomings of sim-

–

1 ple visual inspection, and highlight the need for

0 45°N –2000 m

0 more rigorous and objective numerical methods 0 for differentiating proﬁ les. Gerber et al. (2009)

m developed a morphodynamic model that pre- dicts submarine canyon-and-channel longitudinal profi les affected by continental-margin progradation and the downslope evolution of turbidity currents. Such a model is an important step toward assessing the relative contributions 130°W 120°W 110°W of forcings to longitudinal-profi le character, including preexisting depositional relief, margin B 0 200 400 MILES evolution, and erosional sedimentary processes. Subsequent modeling efforts should focus on 0 200 400 KILOMETERS Eastern balancing those effects with tectonic uplift and North America 50°N deformation (cf. Fig. 9). Such models can be used in order to more precisely and meaning- Glacia fully differentiate profi les and test some of the lly ex c interpretations of this study, which were devel- av a oped from more empirical observations and te d ch quantifi cation of profi les. a n Laurentian n e l system CONCLUSIONS Scotian shelf Canyon-and-channel systems on the mod- –1000 m ern seafl oor, and their characteristic longitudinal profi les, refl ect processes and forcings that operated approximately since the last glacial cycle, for example, sediment–gravity-fl ow ero- –5000 m 40°N sion (Fig. 9). However, effects of the more distant past can also have a profound infl uence on more recent sediment-delivery systems by 70°W 60°W 50°W establishing the seafl oor template across which canyons and channels develop (Fig. 9). Longi- Figure 10. High-latitude continental margins conducive to the development of exceptionally tudinal profi le groups generally correspond with concave canyon-and-channel longitudinal profi les. (A) Western North America topography continental-margin types and depositional archi- and offshore Cascadia margin bathymetry from GeoMapApp, http://www.geomapapp.org tectures, with a few exceptions. Furthermore, our (Ryan et al., 2009b). Contour interval is –1000 m. Columbia River drainage basin is outlined assessment of methods of grouping profi les indi- in white. Astoria (7) system is a dashed white line offshore (Nelson et al, 1970). (B) Scotian margin cates that empirical observations of profi les are bathymetry offshore eastern North America from GeoMapApp, http://www.geomapapp.org an effective means of constructing groups that (Ryan et al., 2009b). Contour interval is –1000 m. Notice the prominent glacially excavated have some predictive capability of continental- channel leading to the Laurentian (13) system (dashed white line; Skene and Piper, 2006). margin type and depositional architecture. How- ever, exceptional longitudinal profi les dominated by erosional sedimentary processes highlight the need for more rigorous and objective numerical methods for differentiating profi les and

330 Geosphere, April 2011 Canyon-and-channel longitudinal profi les assessing controls on their development. Results Covault, J.A., Romans, B.W., Fildani, A., McGann, M., and Huyghe, P., Foata, M., Deville, Mascle, G., and Caramba of this study provide a new catalog of the breadth Graham, S.A., 2010, Rapid climatic signal propaga- Working Group, 2004, Channel profi les through the tion from source to sink in a southern California sedi- active thrust front of the southern Barbados prism: and general controls of the shapes of submarine ment-routing system: The Journal of Geology, v. 118, Geology, v. 32, p. 429–432. sediment-delivery systems, which can be related p. 247–259, doi: 10.1086/651539. Inman, D.L., 2008, Highstand fans in the California border- Dahlen, F.A., Suppe, J., and Davis, D., 1984, Mechanics of land: Comment: Geology, Online Forum, e166. to the depositional architecture of different con- fold-and-thrust belts and accretionary wedges: Cohe- Inman, D.L., and Jenkins, S.A., 1999, Climate change and tinental margins. sive Coulomb theory: Journal of Geophysical Research, the episodicity of sediment fl ux of small California v. 89, p. 10087–10101, doi: 10.1029/JB089iB12p10087. rivers: The Journal of Geology, v. 107, p. 251–270, ACKNOWLEDGMENTS Damuth, J.E., 1994, Neogene gravity tectonics and deposi- doi: 10.1086/314346. tional processes on the deep Niger Delta continental Klaus, A., and Taylor, B., 1991, Submarine canyon devel- The authors would like to thank the Clastic Stra- margin: Marine and Petroleum Geology, v. 11, p. 320– opment in the Izu-Bonin forearc: A SeaMARC II and tigraphy Research and Development Team at Chevron 346, doi: 10.1016/0264-8172(94)90053-1. seismic survey of Aoga Shima Canyon: Marine Geo- Dartnell, P., Normark, W.R., Driscoll, N.W., Babcock, J.M., physical Researches, v. 13, p. 131–152. Energy Technology Company (ETC) and the larger Gardner, J.V., Kvitek, R.G., and Iampietro, P.J., 2007, Lambeck, K., and Chappell, J., 2001, Sea level change family of Earth scientists at ETC. In particular, Julian Multibeam Bathymetry and Selected Perspective through the last glacial cycle: Science, v. 292, p. 679– Clark, Angela Hessler, Michael Pyrcz, Brad Ritts, Will Views Offshore San Diego, California: U.S. Geologi- 686, doi: 10.1126/science.1059549. Schweller, and Yongjun Yue shared ideas, comments, cal Survey Scientifi c Investigations Map 2959, http:// Laursen, J., and Normark, W.R., 2002, Late Quaternary and stimulating discussions with the authors. 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MANUSCRIPT RECEIVED 4 MAY 2010 tems and implications for the architecture of deepwater Shanmugam, G., and Moiola, R.J., 1988, Submarine fans: REVISED MANUSCRIPT RECEIVED 24 OCTOBER 2010 reservoirs: Gulf Coast Section SEPM (Society of Sedi- Characteristics, models, classifi cation, and reservoir MANUSCRIPT ACCEPTED 17 NOVEMBER 2010

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