Smith (1939)— see also Smith (1939, 1940a, 1940b, 

 1941). 



The origin of these canyons is still an open ques- 

 tion, but most recent authors Ijelieve that they were 

 formed by a combination of fluvial processes deliv- 

 ering sediment during lower stands of the sea and 

 submarine transport of the sediment by mass move- 

 ment and turbidity currents seaward of the shelf. 

 Review articles on the canyons as well as on the 

 Continental Slope and Rise have been made by 

 Johnson (1938-1939, 1939), Veatch and Smith 

 (1939), Stetson (1949), Deitz and Menard (1951), 

 Dietz (1952, 1963a), Kuenen (1953), Drake et al. 

 (1959), Heezen et al. (1959), Shepard (1963), 

 Guilcher (1963a, 1963b), Heezen (1963), Moore 

 and Curray (1963), Hoskins and Hersey (1965), 

 Emery (1966b), Krause (1966), and Heezen, Hol- 

 lister, and Ruddiman (1966) . 



The surface sediments of the slope and canyons 

 consist of rock outcrops, deltaic deposits, and 

 slumping debris, all of which are more or less 

 covered by a veneer of late Pleistocene and present- 

 day muds and organic oozes. 



Terraces and Shore Features 

 on the Inner Shelf 



For the most part the inner shelf is made up of 

 alluvial plains that have been modified by glacial 

 outwash and by the Holocene transgi-ession. Much 

 of this has been discussed in preceding sections, 

 but some of the better defined features deserve fur- 

 ther mention. Although trausgressive featui'es oc- 

 cur on the inner shelf at almost every level between 

 the present shore and about 40 fm., they seem to 

 be concentrated in at least four major bands that 

 occur at about 6 to 15, 15 to 27, 28 to 33, and 33 

 to 40 fm. 



The shallowest of these bands (6-15 fm.) has 

 been described by McMaster and Garrison (1967) 

 who noted evidence of a barrier spit and lagoon 

 south of Block Island at about 13 fm. (chart 

 0808N-51 ) . Similar spits can also be found at about 

 13 fm. southeast of Cape May (chart 0807N-56), 

 across the Great Egg Harbor River Channel and 

 east of Brigantiue Shoal (chart 0807N-55 ), south- 

 east of Montauk Point (chart 0808N-53), east of 

 Point Judith and south of Nomans Land (chart 

 0808N-51). Furthermore, Elliott ctal. (1955) have 

 noted a ridge, which crosses tlic Delaware Channel 

 at a depth of about 15 fm., and luive suggested that 



this ridge may be the remains of a submerged 

 coastal terrace ( chart 0807N-57 ) . 



The 6- to 15-fm. band is also well represented 

 by channel bars and small depressions off the coasts 

 of Delaware and New Jersey, by the barred terrace 

 below Cholera Bank south of western Long Island 

 (chart. 0808N-55), by the tidal delta between 

 Martha's Vineyard and Nantucket Island (chart 

 0808N-51), and by the higher parts of Nantucket 

 Shoals. Most of these features are probably of late 

 Holocene age. 



The second band (15-27 fm.) is represented by : 

 many apparent channel bars, barrier beaches, and 

 lagoons oft' the coasts of Delaware and southern 

 New Jersey ; by spits and bars above Tiger Scarp 

 (chart 0807N-52) ; by Cox Ledge south of Nar- 

 ragansett Bay and the tidal deltas in the Block 

 Channel system (chart 0808N-51) ; and by a plat- 

 form witli numerous sand ridges south of the south- 

 eastern part of Nantucket Shoals (chart 0708N- 

 52). These features are probably of Holocene age, 

 with the possible exception of the platform south 

 of Nantucket Shoals. This platform may represent 

 the old silt beds under the Shoals and may be as 

 old as the Sangamon (Livingstone, 1964) ; how- 

 ever, its covering of sand ridges is probably Holo- 

 cene (Groot and Groot, 1964). 



A Holocene age estimate for the features in this 

 band is supported by the discovery of fossil oysters, 

 Crassostrea rirginica, some with radiocarbon ages 

 of 7,300 to 10,300 years, at depths of 18 to 24 fm. 

 throughout the mapped area (Merrill et al., 1965: 

 Emery and Garrison, 1967). Living oysters of this 

 species are found almost entirely in shallow in- 

 shore waters. Old fresh-water peat deposits, with 

 radiocarbon ages of 8,600 to 11,000 years, have 

 also been found in this band on Nantucket Shoals 

 (Emery. Wigley, Bartlett, Rubin, and Barghoorn, 

 1967)." 



The third band (28-33 fm.) is represented by 

 bars and lagoons oft' southern New Jersey and by 

 barred terraces south of Long Island and Massa- 

 chusetts. These features are also probably of Holo- 

 cene age. Fossil oysters, some with radiocarl)()n 

 ages of 9,800 to 10,800 years, have been found con- 

 centrated in this band throughout the area (Mer- 

 rill et al., 1965; Emery and Garrison, 1967). An 

 old peat deposit has been found at a depth of about 

 32 fm. on Georges Bank, just to the east of the 

 region discussed in the present report : this has a 



60 



U.S. FISH AND WILDLIFE SERVICE 



