The Natural Range of Submarine Canyon-And-Channel Longitudinal Profi Les
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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 da tion 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. For permission to copy, contact [email protected] 313 © 2011 Geological Society of America Covault et al. 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. 4 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.