SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES ? NUMBER 11 Underwater Television Survey of the Atlantic Outer Continental Margin near Wilmington Canyon Daniel J. Stanley and Peter Fenner AUGf SMITHSONIAN INSTITUTION PRESS City of Washington 1973 ABSTRACT Stanley, Daniel J., and Peter Fenner. Underwater Television Survey of the Atlantic Outer Continental Margin near Wilmington Canyon. Smithsonian Contributions to the Earth Sciences, number 11, 54 pages, 18 figures, 1973.? The study summarizes the results of an underwater television survey of the sea floor at the shelfbreak and at the head of Wilmington Canyon off the Middle Atlantic States. Distributions are shown for bottom currents and sedimentary structures, suspended matter, bottom firmness, bottom lithology, shell percent- age, and fauna. A number of man-made objects on the sea floor in this area is documented. The Appendix is a listing of observations made at 26 stations. These data, based on direct visual observation of the sea floor, serve to comple- ment earlier marine geological investigations made in this region. Mapping shows that surficial outer shelf and canyon head sediments at the shelfbreak are undergoing modification by both bottom current processes and bioturbation and that at the present time the Wilmington Canyon is receiving sediment mainly from the adjacent margin. Gravel, oyster banks, and near-vertical cavernous cliffs occurring at depths between 100 and 200 m are relict features related to eustatic changes of sea level that affected the outer continental margin during the Pleistocene. OFFICIAL PUBLICATION DATE is handstamped in a limited number of initial copies and is recordedin the Institution's annual report, Smithsonian Year. SI PRESS NUMBER 4785. SERIES COVER DESIGN: Aerial view of Ulawun Volcano, New Britain. Library of Congress Cataloging in Publication Data Stanley, Daniel J.Underwater television survey of the Atlantic outer continental margin near Wilmington Canyon.(Smithsonian contributions to the earth sciences, no. 11) 1. Continental margins?United States. 2. Television in oceanography. I. Fenner, Peter,1937? joint author. II. Title. III. Series: Smithsonian Institution. Smithsonian con- tributions to the earth sciences, no. 11.QE1.S227 no. 11 [GC84.2.U5] 550'.8s [551.4'614'6] 72-13421 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 - Price 65 cents (paper cover) Underwater Television Survey of the Atlantic Outer Continental Margin near Wilmington Canyon Daniel J. Stanley and Peter Fenner Introduction This publication represents an effort to make available in one place all of the source data ob- tained during an underwater television survey as one of a series of investigations concerned with sedi- mentation patterns on the outermost reaches of the broad continental shelf bordering the Middle At- lantic States. Direct visual observations relating to bottom sediment types and the distribution of faunal elements are presented here for the first time. The present series of investigations includes a morphologic and subbottom reconnaissance (Kel- ling and Stanley, 1970), a photographic and bottom- sampling program (Stanley and Kelling, 1968), and water-mass configuration and movement studies (Fenner et al., 1971; Lyall et al., 1971). Direct ob- servation of bottom neocurrent activity, water-mass movement, and sediment transport was made by underwater television and was in part reported on elsewhere (Stanley et al., 1972). This, a relatively novel observational technique, has been used with success in other areas (Stamp, 1953; Eddy et al., 1967; Drapeau, 1970). The specific area we examined by the underwater television technique is about 175 km southeast of Delaware Bay, at the head of Wilmington Canyon Daniel J. Stanley, Division of Sedimentology, Smithsonian Institution, Washington, D. C. 20560. Peter Fenner, Governors State University, Park Forest South, Illinois 60466. and at the break between the outermost continental shelf and upper continental slope (Figure 1). It was selected in accordance with the overall plan for this series, in which successive cruise itineraries were conditioned by the results of previous deter- minations, e.g., of bathymetry, structure and strati- graphic setting, water mass, and bottom type and aspect. Sedimentation in canyons heading in deep water far from land remains enigmatic. Our studies have led us to infer that the head of the Wilmington Canyon has, both now and in the recent geologic past, trapped sediment moving on the outer shelf. The hypothesis that sediment is being funneled downslope through the Canyon was assessed in a previous paper (Stanley and Kelling, 1968). Data presented herein were gathered during a cruise (RoS4) made aboard the USCGC Rockaway (WAGO377) from 11 to 18 July 1968. ACKNOWLEDGMENTS.?We thank the U.S. Coast Guard Oceanographic Unit for ship time and the captain, officers, and men of the USCGC Rockaway for their help in carrying out the work at sea. Dr. G. Kelling, University of Wales, helped in the planning phases of this cruise as well as in the collection of data. We were also aided by Dr. D. J. P. Swift, Marine Geology and Geophysical Laboratory, National Oceanographic and At- mospheric Administration, Mr. J. A. Good, Hydro Products, and Messrs. G. Bloomer, D. Eby, E. Gruenstein, and D. Kersey. Messrs. H. Sheng and SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES 38?40' 38*30' TV STATION (DEPTH IN FATHOMS) N. MILES 2 3 0 12 3 KILOMETERS 73?30' NUMBER 11 <- FIGURE 1 Television stations occupied in and near the head of Wilmington Canyon east of the Middle Atlantic States in July 1968. Data collected along the station tracks are shown in Appendix. Depth in this and other charts given in fathoms (1 fathom ? 1.83 m). L. B. Isham, Smithsonian Institution, helped with drafting. Dr. G. Kelling and Dr. H. D. Palmer, Westinghouse Ocean Research Laboratory, criti- cized the manuscript. We alone take responsibility for errors that may remain. Financial support was provided by Smithsonian Research Foundation grant nos. 233770 and 234230 (D. J. S.) and Gov- ernors State University (P. F.). Area of Study Details of the physiography and topography of the area studied are given by Kelling and Stanley (1970). Figure 1 shows the ship's track at the 26 television stations occupied during a period of very low wind and fairly calm seas. Bottom control, necessary to keep to a planned track, was based on bathymetric records and PESR (Precision Echo Sounding Recorder) records taken continuously throughout the cruise. Methods and Techniques Video monitoring and recording equipment were continuously manned during all times when the underwater television rig was submerged (at depths to 426 m). The system included a light source, suspended penetrometer, and vaned compass at- tached to the frame on which the camera was mounted (Figure 2). The compass (diameter, 7.5 cm) serves as scale. Greenwich Mean Time was used as the basic reference for all notations and recordings of continuously monitored data?bathymetry and bottom-viewing?and for regularly made observa- tions?navigational fixes, course changes, weather observations, and hourly expendable bathythermo- graph, surface-water temperature, and salinity rec- ords. In addition to written notes, the videotape re- corder was used to record a running commentary of sightings, data collected, and speculations on explanations of observations. The audio track of B FIGURE 2.?Photographs on deck of USCGC Rockaway showing underwater rig used on cruise RoS4: A, television gear, mounted in a steel frame (120 cm x 120 cm x 120 cm), and large stabilizing vane was lowered off the stern and kept just above the sea floor as the ship drifted; B, camera (a) [Hydrp Products Model TC 100], 1000-watt mercury vapor light (b) mounted in cage and attached to 460 m long cable. Compass (c) was suspended far enough from frame to be free from the effects of its magnetic field. Tapered and scaled shaft (penetrometer, d) was hung below all other equipment so as to be in view when striking sea floor. SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES FIGURE 3.?Features such as oriented polychaete tubes (Sta- tion 19, 346 m), on upper slope west of the Canyon, provide information on botton currents. In this sequence, note the realignment of tube (in rectangle) resulting from turbulence caused by the cage motion above the sea floor. the videotapes was later found to be extremely helpful in reconstructing observations and organiz- ing conclusions. Details on light and camera angles, technical data on instruments used, and operating conditions for the gear are given elsewhere (Stanley et al., 1972). The photographs in the plates of the pres- ent paper are, for the most part, reproductions of images stored on one tape, transferred to another, kinescoped, photographed, then enlarged and made into new negatives with prints for use here. These fifth generation reproductions have suffered much in the process. Data concerning most variables, save navigational specification (see Figure 1, for all locations), are FIGURE 4.?Sequence of photographs made from video tapes shows turbulence initiated as compass strikes muddy bottom (A) (Station 18, 134 m). After a few seconds (B) mud brought into suspension is slowed by SSE moving current and then (c) the cloud begins movement to the S and SSW (about 10 cm/sec) and out of view. Compass diameter, 7.5 cm. 38?40' 38?30 38?IO' ?? current w ripple marks worm tubes aligned shells (DEPTH IN FATHOMS) N. MILES 012 3 KILOMETERS FIGURE 5.?Chart showing evidence of neocurrent activity in and near the head of Wilmington Canyon (from Stanley et al., 1972). Arrows depict direct observation of sediment movement of currents above the bottom (based on sediment movement or heeling over of sessile fauna). Indirect evidence of recent current activity (based on alignment of ripple mark crests, poly- chaete tubes and aligned shells) is also depicted. SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES listed in the Appendix. Summarized are raw ob- servational and interpretative data such as: station number and physiographic location; date and time; depth; inferred bottom-sediment texture; resistance to penetration (firmness); the nature, orientation, and dimension of ripple marks and other features indicating current movement, including oriented organic structures; velocity of suspended sediment movement along the bottom; nature and distribu- tion of shell fragments; and the relative amounts of materials suspended in the water near the bot- tom. A partly edited, untitled version of a short film, and the more than 20 hours of videotapes from which it was made, are available from the Sedi- mentology Laboratory, National Museum of Natu- ral History. Suspended Matter and Bottom Currents Suspended matter and current activity were ob- served everywhere throughout the area of study? on the outermost continental shelf, shelf break, canyon head proper, and upper slope?but not uni- formly developed. Ripple marks, aligned poly- chaete tubes (Figure 3), and shells were used to infer current directions, and particles streaming along the sea floor past a fixed object of known size provided a means for measuring bottom-current velocities (Figure 4). Data included in the Appen- dix are fully discussed in Stanley et al. (1972). In sum, current activity ranged from barely de- tectable to about 20 cm/sec and did not follow a uniform pattern (Figure 5). There is, however, a net southerly and downslope orientation to cur- rent flow within the Canyon. Medium to large concentrations of suspended matter just above the sea floor (Figure 6) help explain the generally poor clarity of photographs made in earlier surveys of this area (Stanley and Kelling, 1968). Figure 6 de- picts a rather subjective classification of concen- trations of suspended matter, and shows that higher concentrations most often occur higher on the shelf side of the shelfbreak. There is also a suggestion of a slight westward offset of the medium-clarity water from the Canyon axis, particularly in the headward part, which may reflect large scale mo- tion of shelf and slope water in this region during the period of the survey. 38*30' FIGURE 6.?Chart showing distribution of layer of suspension- rich water above the sea floor as observed by television. During the period of the cruise (11 to 18 July 1968) some- what higher concentrations of suspended sediment were noted in the area landward of the shelfbreak than in the Canyon head proper. A slight westward offset away from the Canyon is also observed. Firmness of the Sea Floor Penetration into the sea floor of a scaled stain- less steel shaft (see penetrometer in Figure 2nd) provides a relative scale of bottom firmness. Areas of deep (> 24 cm), medium (15-24 cm), and shal- low penetration (< 15 cm) were thus designated and mapped (Figure 7). Data summarized in the Appendix show that most of the sea floor of the outer shelf and upper- most slope regions not near the Canyon is char- acterized by low to very low penetration. This firm surface is indicative of a shelly, gravelly sand cover. A zone of medium penetration occurs at the very head of the Canyon and along much of its eastern wall to a depth of about 200 to 450 m and appears to be indicative of sandy mud, silt, clay, or mixtures of these grades. The least firm sedi- NUMBER 11 38*30' PENETRATION shollow | 1 dttp medium (DEPTH IN FATHOMS) N. MILES FIGURE 7.?Chart indicating bottom firmness, based on amount of penetration of scaled shaft into the surficial sedi- ment. Generally firmer sediment on the east canyon wall reflects the presence of coarser sediment tongues draping on that wall as opposed to the west wall. ments occur in the Canyon proper and a distribu- tary canyon cut into the shelf west of the head and reflect a soft clay or ooze bottom (Figure 8). On the western margin, the contact between firm and soft surfaces is more abrupt, and tends to occur at a shallower depth than on the eastern wall, ap- pearing near the shelfbreak. Organic mounds and tracks, ripple marks, other primary sedimentary structures, and the nature of the sediment cloud produced by instruments hit- ting the sea floor, all aided in further interpreta- tion of the bottom firmness. These techniques help to define the generally abrupt "mud line," a boundary, despite tradition, not strictly parallel to the shelfbreak. Major Lithological Types The contoured regional distribution of major surficial sediment textural types is shown in Figure FIGURE 8.?Sequence showing deep penetration (at least 24 cm) of scaled shaft in soft sediment on the west wall of the canyon head (Station 16A, 256 m) . 9. The categories shown are: (a) rock ledges (Fig- ure 10) and bedrock obviously discernible directly from the videotapes, and large broken rock talus (Figure 11); (b) admixtures of pebbles, shell and 73*,30' 38*30' FIGURE 9.?Chart showing distribution of major lithological types in the study area. Note presence of rock outcrops in the canyon head near the shelfbreak, and the draping of sand and gravel on the east wall well into the canyon. The "mud-line" is not strictly parallel to the shelfbreak indi- cating that spill-over and off-shelf processes have been active in recent time. FIGURE 10.?Sequence showing cavernous rock outcrop just below the shelfbreak on the west wall of the Canyon (Sta- tion 16, 120-130 m). This unit forms low "cliffs" with a relief of 5 to 10 m, and is populated by numerous fish and occasional lobsters. The rock is poorly consolidated at the surface as indicated by breaking of outcrop by the pene- trometer. NUMBER 11 coarse sand (also directly discernible from tape), locally including finer sediment (Figure 12); (c) admixtures of medium to fine sand and sandy silt, generally indicated by degree of penetration of the penetrometer, and the presence of associated fea- tures such as ripple marks amply illustrated in Stanley and Kelling (1968; and also detected by direct observation when cage is at rest on sea floor); and (d) mud, including silty and stiff clay, as judged by appearance on the monitor, amount of penetration, and as indicated by the character of the mark made on the bottom or the nature of the sediment cloud raised by the cage and suspended instruments (Figure 8). Categories b and c generally include shelly sands. The character of sedimentary structures and or- ganic tracks, burrows and mounds ("lebensspuren") provide additional evidence of the nature of bot- tom sediment type. Views of rock outcrops along the canyon walls provide some of the more spectacular footage of the television tapes. The most obvious outcrops of bedrock occur on the west side of the canyon wall. There, large clifflike protruding edges of some ex- posures of cavernous rock occur at depths ranging from 110 to 135 m (Figure 10). Locally, the ex- posures are sufficiently friable to be easily broken by the weight of the penetrometer. On the eastern side of the canyon, rock exposures were found to be different in character; they form isolated patches with numerous flat-lying surfaces frequently bur- rowed but not particularly cavernous. Texture of the bedrock appears to be medium to fine. The patchy occurrence of outcrops shown in Figure 9 is in part an artifact resulting from the sample net and subsequent plotting. Furthermore, in the areas west of the canyon where we found outcrops, they tended to be continuous, running perhaps for hundreds of meters; on the eastern side, however, the outcrops occur as smaller patches (< 1000 m2) throughout the area where they are plotted. The paired nature of outcroppings across the canyon is also, in part, an artifact resulting from the sample grid. The coarser surficial sediment consisting of gravel and coarse sand (areas of very low penetra- tion) was found covering much of the outermost shelf area in the vicinity of the canyon, in waters generally less than 180 m deep; however, these FIGURE 11.?Rock outcrops of the type shown in Figure 10 fail ("rock fall"), thus producing boulders and cobbles encountered at deeper depths in the Canyon and on the upper slope. Here a sequence of photographs (Station 12, 278 m) show a large (> 1 m diameter) shell-encrusted block resting on mud. Note fish on rock (B) . 10 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES FIGURE 12.?Concentrations of large pelecypod valves including oysters (A) and gravel on the upper slope just west of the Canyon (Station 19, 196 m). These patches of anomalous sediment types are relict deposits probably related to eustatic lower stands of sea level. coarser grade sediments tend to drape into deeper water along the eastern canyon wall. Pebbles and cobbles were observed to depths of at least 320 m at Station 8. Medium to finer grade sand and sandy silt tend to cover the upper margins of the canyon proper and are, in fact, the predominant textural types serving as the upper canyon head fill. This litho- logical type is also the predominant facies in those areas of the shelf not covered by gravel and coarse sand. The predominantly muddy facies are located axi- ally and extend shelfward to depths of about 90 m at the very northward sector of the canyon head. Similarly, mud can be found in tributary canyons entering the canyon proper. The "mud line" can- not be well defined on the west canyon wall because television stations generally did not extend to the same depths as on the east wall (i.e., drift of the ship prevented the television cage from hanging vertically). The sediment textural distribution confirms ear- lier conclusions based on bottom photography (Stanley and Kelling, 1968), subbottom (Kelling and Stanley, 1970) and current studies (Fenner et al., 1971), and more generalized data that sand NUMBER 11 11 spill-over from the outer shelf into the Canyon has continued until recent time and may still be an active process at present. As a result, sand is a predominant fraction in certain parts of the canyon head. Shell Fraction in Surficial Sediments Shell is one of the predominant components of surficial sandy sediment on the continental shelf. This fraction, mostly whole or fragmented disar- ticulated pelecypod valves, accounts for more than 30 percent of the total sediment. Shell content tends to vary inversely with depth, the decrease of shell amount coinciding roughly with the break in slope. On the eastern canyon margin, however, the distribution of shell-rich sediment coincides with that of the sand-rich sediment, draping from the shelf edge into deeper water. A scale of relative shell abundance was devised (Figure 13). Outermost shelf sediment was found generally to contain more than 25 percent shell, while patches of shell-deficient sediment occur on the shelf in the vicinity of gravel and coarse sand patches. Local concentrations of large pelecypods and gravel occur between about 130 and 200 m (Figure 12). It is possible that certain of these may be remnant oyster banks of the type found in other sectors of the Atlantic shelf at lesser depths (Mer- rill et al., 1965; Emery, 1968) and dating from low stands of sea level during the Pleistocene Epoch. Fauna and Bioturbation Living fauna is a common element in all video- tapes, and the organic forms observed have been grouped into four generalized categories and their distribution is summarized on Figure 14: (a) non- shelled swimming forms, mostly fish (Figures 10; 15c, D; 17C) and, locally, squid (Figure 16); (b) shelled bottom dwellers, e.g., pelecypods (Figure 38"40'. 38*30' 73",30' 38*4O'/ 28-tOX I I I N >25X (DEPTH IN FATHOMS) N. MILES FIGURE 13.?Chart showing distribution of shell (including whole and fragmental matter) , in surficial sediment. Note rapid decrease in shell percentage in water depths below shelfbreak. 38*30" cru.tac.ans \JIJ\ ^ypoj:ChlnOld>1 []?] ?l?h n??ft (DEPTH IN FATHOMS) N. MILES KILOMETERS FIGURE 14.?Distribution of major benthic organisms as ob- served with television. Note sharp faunal breaks between th~ outer shelf and the Canyon head. 12 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES FIGURE 15.?Organisms in the water mass above the sea floor: A, concentration of planktonic forms at northern end of Canyon head (Station 7, 238 m) ; B, shrimp on east wall of Canyon (Station 11A, 302 m) ; c, D, school of small fish on the upper slope west of Canyon (Station 19, 347 m). 12), bryozoans, and echinoderms; (c) soft-bodied bottom dwellers, e.g., sea pens (Figure 17A), CO- elenterates (Figure 17B), and worms; (d) crusta- ceans, including mainly crabs (Figure 17D), shrimps (Figure 15B), lobsters, and sea spiders. The nonshelled swimming forms are most com- mon just within the Canyon proper, and especially on the west margin of the Canyon. Localized con- centrations of fish and plankton (Figure 15A) are also noted on the shelf north of the canyon re- entry. Like the fish themselves, fish "nests" are concentrated in fine-grained sediment below the shelfbreak. As detailed in the previous section, pelecypod and related fragments dominate the sur- ficial shelf sediments and decrease notably beyond the shelfbreak. The distribution of echinoderms is generally irregular and patchy, but locally single faunal types predominate (see Appendix). Crustaceans are more commonly observed below the shelfbreak, the larger forms (i.e., lobsters) fre- quently concentrating in or near the cavernous rock outcrops where benthic fish are also abundant. Sea pens and coelenterates are limited depth- wise below the shelfbreak and, together with worms, are most abundant in finer grained sedi- ment within the Canyon. They locally dominate FIGURE 16.?Sequence showing squid moving past television cage and releasing ink, in the head of Canyon (Station 6, 148 m). the faunal assemblage along the west margin of the Canyon. One area distinguished by this as- semblage was also observed just northeast of the very head of the Canyon. The concentration of worm burrows increases canyonward beyond the shelf break (Stanley, 1971a). These burrowing or- ganisms not only modify the strength of sediment, but also contribute to the addition of suspended sediment in the water mass (worms were seen eject- ing small clouds of mud as the cage moved slowly above the bottom). Fish also were seen stirring the bottom, and they are important in modifying the sea floor and contribute in a small way to the sedi- ment in suspension (Stanley, 1971b). Man-made Objects Human artifacts constitute minor but, in our opinion, significant components of the sea floor in the study area which lies below the east coast shipping lane. Considering our very limited field of view, even the dozen or so whole, large, objects observed during a 5-day period suggest that there is a growing amount of material accumulating even at this distance from shore. Observations of such materials included bottles (Stations 5, 12), cans (Station 3A), paper (Station 19; Figure 18), and a large polelike object. Ma- terials of smaller size were not recorded, and in most cases would have been very difficult to ob- serve due to the camera's motion through the water. The high percentage of artificial fibers filtered from water samples collected in this area on a subsequent cruise (Lyall et al., 1971) attests to the importance of man-introduced materials on this sector of the outer continental margin. Fenner et al. (1971) have shown that this region is one of significant bottom-current activity, hence we can speculate that only a short period of time has elapsed since the objects observed were de- posited. The origin of one bottle with a distinct shape was identified, though not recorded on video- tape (this type of bottle had been commercially 14 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES D FIGURE 17.?Example of benthic organisms in the study area: A, large worm tubes extruding from the sea floor on east wall of Canyon (Station 8, 320 m) ; B, anemones on uppermost slope east of Canyon (Station 12, 312 m) ; c, benthic fish (outlined) extending out of large mud depression on west wall of Canyon (Station 13, 267 m) ; and D, crab moving past penetrometer on upper slope east of Canyon (Station 12, 311 m). introduced only a half-year or so before the cruise). Considerably more man-made objects are presuma- bly buried in the sediment. Conclusions Examination of the sea floor and mapping of the outer Atlantic margin near the head of Wilming- ton Canyon with underwater television supple- ments observations made in earlier surveys of this region. Among features of particular interest are: (1) the apparent intensity of bottom-current ac- tivity and the abundance of suspended matter above the sea floor in the depth range from G5 to 430 m, even though the survey was made in very calm weather and low sea state; (2) the abundance of benthic organisms and intensity of reworking (bioturbation) throughout the study area; (3) the draping of sandy sediment tongues on the east wall into the Canyon axis, and the shallower position of the "mud line" near the shelfbreak on the west Canyon wall; (4) the exposure of cavernous rocky NUMBER 11 15 cliffs on the west wall concentrated between 110 and 135 m depth; (5) the concentration of pelecy- FIGURE 18.?Sequence (A-C) of videotape showing compass catching long paper on the upper slope west of Canyon (Station 19, 200 m) . pods, including oysters, and gravel in pockets be- tween 130 and 200 m; and (6) the significant number of large man-made objects even in this area located far from land. The first three observations listed above indi- cate that surficial sediments, including sand, are being actively moved by the water mass and con- tinuously reworked by organisms. This current ac- tivity results in a net downslope transport from the shelf edge onto the upper slope and into the Wilmington Canyon proper. Spill-over from the shelf onto the east Canyon wall is prevalent. Or- ganisms apparently accelerate this off-shelf process by modifying the physical properties of the sedi- ment wedge. The submerged cliffs, gravels, and oyster banks are relict features resulting from events related to eustatic lowering of sea level in Pleistocene time. The cliffs are at depths that suggest that they were subaerially exposed river- and ocean-cut bluffs. The gravels, undoubtedly of river origin, help pinpoint the position of fluvial deposits and coarse deltaic concentrations formed at the shelfbreak by major rivers that drained the northeastern United States and traversed the subaerially exposed continental shelf during the Pleistocene. The localized oyster "patches" and other pelecypod concentrations were also formed when sea level was considerably lower (at least about 120 m lower), in Wisconsin time. The presence of man-made objects on the sea floor below shipping lanes is not in itself surpris- ing. It does serve to emphasize, however, the im- portance of this type of refuse as an important ele- ment of surficial sediments and one likely to increase unless dumping from ships is more tightly controlled. Underwater television has proved a valuable tool, and its use by marine scientists who plan recon- naissance mapping and regional surveys is advo- cated. Nothing can surpass this direct visual examination of the ocean floor. Literature Cited Drapeau, G. 1970. Sand Waves on Browns Bank Observed from the Shelf Diver. Maritime Sediments, 6:90-101. Eddy, J. E., V. J. Henry, J. Hoyt, and E. Bradley 1967. Description and Use of an Underwater Television System on the Atlantic Continental Shelf. U. S. 16 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES Geological Survey Professional Paper, 575-C:G72- C76. Emery, K. O. 1968. Positions of Empty Pelecypod Valves on the Con- tinental Shelf. Journal of Sedimentary Petrology, 4:1264-1269. Fenner, P., G. Kelling, and D. J. Stanley 1971. Bottom Currents in Wilmington Submarine Can- yon. Nature, Physical Sciences, 229:52-54. Kelling, G., and D. J. Stanley 1970. Morphology and Structure of Wilmington and Bal- timore Submarine Canyons, Eastern United States. Journal of Geology, 78:637-660. Lyall, A., D. J. Stanley, H. N. Giles, and A. Fisher, Jr. 1971. Suspended Sediment and Transport at the Shelf- break and on the Slope. Marine Technology So- ciety Journal, 5:15-27. Merrill, A. S., K. O. Emery, and M. Rubin 1965. Ancient Oyster Shells on the Atlantic Continental Shelf. Science, 147:398-400. Stamp, W. R. 1953. Underwater Television. Scientific American, 188: 32-37. .Stanley, D. J. 1971a. Bioturbation and Sediment Failure in Some Sub- marine Canyons. Vie et Milieu, supplement 22, 541-555. 1971b. Fish-produced Markings on the Outer Continental Margin East of the Middle Atlantic States. Journal of Sedimentary Petrology, 41:159-170. Stanley, D. J., P. Fenner, and G. Kelling 1972. Currents and Sediment Transport at the Wilming- ton Canyon Shelfbreak, as Observed by Underwater Television. Pages 621-644 in D. J. P. Swift, D. Duane, and O. H. Pilkey, editors, Shelf Sediment Transport: Process and Pattern. Stroudsburg, Pennsylvania: Dowden, Hutchinson & Ross. Stanley, D. J., and G. Kelling 1968. Photographic Investigation of Sediment Texture, Bottom Current Activity, and Benthonic Organisms in the Wilmington Submarine Canyon. U.S. Coast Guard Oceanographic Report, 22: 95 pages. Appendix PAGES 17-28 Data recorded on videotape at 26 stations, outer continental margin near Wilmington Canyon (period 12 to 16 July 1968 on USCGC Rockaway cruise RoS4) . See Figure 1 for station location. 18 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES E | ?e "E 3 ? S: -es ismse a Org co ati 5 S 2 a -s M 4J 13 M- ?2 s S o ? .5 I! III I 6B S 3 ?S re NUMBER 11 21 ? 1 B i o o D O U O -3 ?> a e a ~ E J3 -? as 2 A 2 C ?n ?^ "3 ?a a-s-g s - a 22 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES K ?S c "2?? e 1 s t3 Ca S3JL 1K and E tuv: O ? Drift from Log I3 arks 3 '?5, HO 'a E .S"3 ?S ion rbat ^3 (5 shell o 1 pen ?, I5"S ?g *<> ^> ?5?E ?S^~ compass ?ft F) in fm K ___ -5"3 _e co U 73pi J 5 g 3 .y a T3 S g c is 3 U 3 !" J3 'S ? a " s ^ u M S y ? jj S ?f & M a a E s a M CM ? ? n S I ., e e ?? u *3 S >2 ^ SEi ai TJ< to oo t oit en o> o i?i ? ?-? CM CM NUMBER 11 S M ? ? 8 S g8 B e is _ s g -E -S i a 3l ?3 ? B s s -a K s a??? 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