56 Fred B Phleger 



Some useful generalizations may be made from these data. The amount of post- 

 glacial deposition is smallest away from the major source of supply, the Mississippi 

 River, and near the centre of the basin ; there is a general increase in amount of 

 deposition closer to the source, as expected. In all but one core shoaler than 1,400 m 

 the coring tube did not penetrate through post-glacial sediment. There is considerable 

 local variation in the amount of post-glacial deposition. For example, in core 5 in the 

 basin there is two to four times as much post-glacial deposition as in nearby cores 

 from similar depths. Core 14 on the upper part of the continental slope has consider- 

 ably less post-glacial sedimentation than nearby cores at similar depths and position. 

 The amount of post-glacial deposition in the cores from the basin and lower continental 

 slope in the present cores is comparable to that shown in cores from the basin and 

 lower slope reported previously from the northwestern area (see Phleger, 1951, 

 Figs. 29-33). The amount of such deposition on the upper slope appears to be larger 

 than in the western area, although there are exceptions. 



Cores 9 and 10 contain sediments and faunas in their lower sections which appear 

 to have been displaced downslope from shoaler depths, presumably in the form of 

 turbidity currents. The presence of abundant sand, wood fibres and abundant shallow- 

 water benthonic Foraminifera at water depths of 1,298 m and 1,372 m appears to be 

 conclusive evidence for such displacement. Most of the benthonic Foraminifera are 

 species normal for the depth at which the core was taken ; this demonstrates that the 

 displaced material was deposited at the present water depths at those stations. The 

 age of the displacement is post-glacial (W 1), as shown on Fig. 3. 



Cores 9 and 10 occur in the bottom of Mississippi Canyon (Fig. 2). Other cores 

 in this traverse do not have displaced sediment, at least in significant amounts, and 

 these are located on topography other than the canyon floor. This suggests that the 

 turbidity flow was localized in the canyon. Studies by Shepard (1951) and Ludwick 

 (1950) in the San Diego area have shown that displacement of sediment from shallow 

 to deep water appears to be funnelled down the canyons in that area, and it seems 

 probable that much displaced sediment flows down the channels of submarine canyons 

 in other areas of the world. The restriction of displaced sediment to the Mississippi 

 Canyon floor in the present cores is evidence in this connection. 



The lower section of core 15, below approximately 165 cm, contains abundant sand 

 grains and plant fibres; this sediment contains no benthonic Foraminifera which are 



