DROWNED VALLEYS OR FJORDS. Ill 



From the Susquehanna the special study of the writer begins. Its 

 okl cliannel is now buried and passes under the i)eninsuhi of INhirjdand, 

 where the deposits of sand have extended the surface of tlie hind. Tlie 

 coastal currents have done much to obscure the old channels by dei)osit- 

 ing sand in them, for the water is deeper than 200 or 300 feet only on 

 approacliing the margins of the continental shelves, and there, as well as 

 on the lower sloi)es of the plateaus, the drowned valleys reappear. Thus 

 the Susquehanna fjord is 6,420 feet where the plateau rises 1,800 feet 

 above the channel. iVgain, where the depth reaches 9,846 feet, the rocky 

 boundary of the canyon is still 1,500 feet above its drowned floor. Even 

 at 12,000 feet the fjord opens into an embay ment in the edge of the 

 plateau, and has a width of 40 or 50 miles, or about that of the lower 

 Mississii)pi flood-plain. 



The fjords of Blake plateau are especiall}^ remarkable. In spite of 

 the tendency of the Gulf Stream to silt up the transverse channels 

 and the flUing produced b,y the coastwise drifting sands, and in spite of 

 the sometimes incomplete soundings, several im^jortant drowned vallej^s 

 have been discovered. The Santee and Pee Dee rivers formerly joined 

 and cut a dee]) channel across Blake plateau, the soundings indicating 

 channels still open to the depth of several hundred feet. The old Sa- 

 vannah valley has cut its way through the whole remnant of Miocene 

 formation, as shown by well-borings submitted to Mr Louis W^oolman, 

 who has found in the higher limestones the characteristic microscopic 

 Upi)er P]ocene shells, and is now buried to a depth of 250 feet by more 

 recent sandy deposits. We do not know that this is the greatest depth, 

 since the wells may not be in the center of the buried valley, which is 

 several miles wide. Crossing Blake plateau, a submerged valley in line 

 with the Savannah embayment is still left open to a depth of over 1,650 

 feet, with the ])lateau de})ressed to 1,950 feet more below the surface of 

 the sea. After traversing Blake plateau for a distance of 250 miles, this 

 tjord enters the deep embayment in the edge of the continental shelf. 



Another remarkable submarine valley is that in line with Altamaha 

 river.* At a point where the i)lateau is sul^merged 2,500 feet this canyon- 

 like depression reaches a depth of more than 7,800 feet beneath the sea- 

 level, and 300 miles farther off" shore tlie depth is 13,560 feet, with the 

 outer embayment considerably dee})er. This valley is comi)aral)le to the 

 canyon of the Colorado river of the west. The depression which the 

 writer has called the Bahaman fjord also crosses the same plateau just 

 north of the group of small insular remains of the coastal plain which 



• Eastward of thi« region the soun<lings are not numerous, hut at the edge of the phiteau evidence 

 appears to show that tiie canyon is much deeper. Although tliis depression at 7,800 feet is not con- 

 firmed hy ft chain of soiindin;?s, its a))S<'nce would not aHect any other portion of the argument, us 

 it was an after observation. 



XVI-FiuM,. (iy.DL. Soc. Am.. Voi,. G, 1894. 



