Terrains Southwest of the Hudson Channel 



Off the coasts of New Jersey, Delaware, and 

 Maryland, the bottom above about 50 fm. consists 

 of alternate ridges and longitudinal depi-essions, 

 whicli generally run northeast-southwest and are 

 interspaced by flat areas, escarpments, embay- 

 ments, and former channels. The sediments on 

 this part of the shelf are predominantly sands 

 with some coarser material. Muds are infrequent 

 above about 50 fm. and are not dominant shal- 

 lower than the shelf break. 



The terrains in this area are similar to present 

 nearshore and modified subaerial alluvial terrains ; 

 this similarity is not surprising because the surf- 

 zone, the complex of lagoons and coastal marshes, 

 and the subaerial river regimes must have repeat- 

 edly migrated back and forth acro.ss the shelf. 

 Flint (1940) noted that north of the James River 

 the Pleistocene formations on the emerged coastal 

 plain are typical of compound alluvial deposits. 

 It seems that this is also true of the submerged 

 shelf, with the addition of numerous transgressive 

 marine features (see also MacClintock, 1943, and 

 Schlee, 1964) . 



Delaware River channels. — From the mouth of 

 Delaware Bay a channel may be traced south- 

 eastward about 40 nautical miles (Lindenkohl, 

 1891; charts 0807N-56 and -57). Below 20 fm. 

 this channel is lost in a series of what appear to be 

 old lagoons and barrier beaches which continue 

 down to about 40 fm. To the northeast the chan- 

 nel is bounded by a scarp as much as 15 fm. high. 

 A well-defined ridge backing this scarp can be 

 traced 30 nautical miles soutlieastward from Cape 

 May, and its remnants extend for another 30 or 40 

 nautical miles. 



Northeast of this ridge is a shallow embayment 

 that has a diffuse channel below 5 to 7 fm. (charts 

 0807N-55 and -56). Deeper than 20 fm. this 

 embayment flattens out and merges with what 

 appears to be a series of lagoons and barrier 

 beaches. Possibly this bay represents an older Dela- 

 ware River estuary which might be correlated 

 with a post-Sangamon channel in the Cape May 

 Formation on the Cape May Peninsula (Rich- 

 ards, 1962). 



Great Egg Ilarhor Hirer rhannel. — Running 

 southeast from near Great Egg Harbor Inlet is 

 a smooth embayment that extends to a depth of 

 12 or 14 fm., where a bar has been built across its 



54 



mouth (chart 0807N-55). Beyond this bar the bay 

 narrows and a shallow channel continues south- 

 southeastward. Between 18 and 22 fm. a ridge, 

 about 20 nautical miles long, appears to have been 

 a large barrier beach. It encloses what was prob- 

 ably a former lagoon, now as much as 2 or 3 fm. 

 deeper than the surrounding bottom. Below this 

 feature, the channel is lost in a deeper series of 

 what seem to be lagoons and barrier beaches. The 

 northeast boundary of the embayment off Great 

 Egg Harbor Inlet is a low ridge extending south- 

 easterly from Brigantine Shoal ; it appears to be 

 composed of a series of submerged sand spits and 

 barrier beaches. 



The old and new Delaware embayments and the 

 Great Egg Harbor embayment are each well 

 defined between about 10 and 20 fm. Below about 

 20 fm., however, the new Delawai-e embayment is 

 lost, and the old Delaware and Great Egg Harbor 

 embayments are combined, first into a large shal- 

 low depression (about 35 nautical miles long) 

 between 24 and 27 fm. and then into a single open 

 embayment between 27 and 29 fm. (charts 08O7N- 

 55 and -56). Below about 28 fm., this open embay- 

 ment narrows into a slender channel which con- 

 tinues southward to about 35 fm., where it is lost 

 in what may be a comjalex of fonner lagoons. 



The Shelf northeast of Brigantine Shoal. — 

 Northeast of Brigantine Shoal the shelf is domi- 

 nated by several large northeastward trending 

 embayments, and by two north-south trending 

 channels, which are associated with a submerged 

 alluvial gravel deposit (Schlee, 1964; charts 

 0807N-54 and -55) . One of the north-south trend- 

 ing channels heads offshore near lat. 39°45' N. and 

 may be traced southward for about 30 nautical 

 miles, roughly along long. 73°50' W. 



West of this channel is a very smooth and flat "1 

 plain, whose shallow limit is defined by the 10- or 

 11-fm. isobath. On the east it is bounded by a low- 

 scarp and backed by a north-south ridge with a 

 minimum depth of less than 9 fm. This ridge is 

 distinct for at least 35 nautical miles along the 

 l^ottom, and remnants of it extend even farther 

 both nortli and south. 



East of this ridge is the second of the north - 

 south channels mentioned above. It originates near 

 lat. 39°50' N. and runs southward for about '-W 

 nautical miles between long. 73°28' and 73°33' ~\V. 

 This channel is defined by the 19- to 21-fm. iso- 



U.S. FISH AND WILDLIFE SERVICE 



