I. INTRODUCTION 



Submarine canyons are large, steep-sided, 

 generally sinuous depressions incised into the 

 continental slope and rise and often heading on 

 the shelf. They occur on the margins of most 

 continental regions and their mode of origin 

 has long been a source of debate and contro- 

 versy among geologists and others concerned 

 with the morphology of the sea floor (Lawson, 

 1893; Pruvot, 1894; Daly, 1936; Johnson, 1938; 

 Kuenen, 1950; Shepard, 1963; and others). 

 More recently it has been suggested that sub- 

 marine canyons are responsible for funnelling 

 sediment from shallow shelf regions, down the 

 continental slope and onto the deep ocean floor 

 of the rise and abyssal plain beyond (Shepard, 

 1965a). Submarine canyons best studied to 

 date are of the type that head on relatively 

 narrow shelves in tectonically active areas 

 (Shepard and Dill, 1966). Canyons located off 

 wide shelves in structurally stable areas have 

 received less attention. 



A program of investigation undertaken by 

 staff of the Division of Sedimentology, U.S. 

 National Museum, Smithsonian Institution, 

 with active cooperation and support of the U.S. 

 Coast Guard Oceanographic Unit, has as long- 

 term objective, the detailing of the geometry 

 and sedimentary processes associated with can- 

 yons in general. One of the major purposes of 

 this study is the formulation of a sedimentary 

 model for modern canyons located on shelves 

 off low coastal regions which are apparently 

 tectonically stable. Four submarine canyons 

 (from North to South: Wilmington, Baltimore, 

 Washington and Norfolk) located on the At- 

 lantic seaboard of the United States southeast 

 of Delaware and Chesapeake Bays are of parti- 

 cular interest in this respect (see inset, Fig. 1). 

 All four of these canyons, mapped in consider- 



able detail by Veatch and Smith (1939), are 

 deeply incised as much as 12 nautical miles 

 into the outer edge of the wide continental 

 shelf. The canyons form two distinct paired 

 systems (Wilmington-Baltimore and Washing- 

 ton-Norfolk), each consisting of a long and a 

 closely associated shorter canyon, as noted by 

 Pratt (1967). The selection of these specific 

 canyons for study was, in part, determined by 

 logistics, i.e., their proximity to major ports 

 which facilitates repetitive runs over the same 

 area and ease of monitoring with different ma- 

 rine geological and oceanographic techniques. 



The cruise described in the following ac- 

 count was made by the USCGC ROCKAWAY 

 (WAGO 377) during the period 4 to 10 Decem- 

 ber, 1967 and is referred to as cruise RoS : . 

 The purpose of this cruise was to obtain photo- 

 graphic records of the ocean floor in the vicin- 

 ity of Wilmington submarine canyon, the most 

 northerly of the 4 features. Free-fall cores of 

 the bottom sediment were also collected at sev- 

 eral of the photographic stations. This, the sec- 

 ond of a series of 5 cruises in this area, was 

 preceded by a morphological-subbottom inves- 

 tigation (RoS,, Kelling and Stanley, in prepa- 

 ration) and followed by bottom sampling 

 (RoS,) and underwater television (RoS,) 

 programs (data presently under examination 

 at the Division of Sedimentology, Smithsonian 

 Institution and Department of Geology, Uni- 

 versity of Wales at Swansea). This report pre- 

 sents photographic data obtained during RoSj 

 and a summary of results. 1 



1 A published presentation made by the authors at 

 the Ocean Sciences and Engineering of the Atlantic 

 Shelf Symposium, Marine Technology Society, Phila- 

 delphia (Stanley and Kelling, 1968b) is an interpre- 

 tative summary of the data presented in this Report. 



