Foraminiferal faunas in cores offshore from the Mississippi Delta 57 



characteristic of water shoaler than that at which the core was collected (298 m). It 

 is possible that this sediment was displaced from shallow water, but the absence of 

 displaced Foraminifera suggests that a turbidity current was not the mechanism of 

 deposition. It appears more likely that this material may be river sediment which was 

 carried offshore (approximately 20 miles) during flood stages of the Mississippi 

 River. Shallow-water Foraminifera would not be expected under these conditions. 



It is suggested that the occasional specimens of shallow-water Foraminifera found 

 in cores 3-8 and 13-14 do not indicate the presence of appreciable amounts of dis- 

 placed sediment in these cores. These specimens may have been deposited by one or 

 more of the following mechanisms : 



(1) They may have been carried somewhat beyond the limit of turbidity flows 

 because of slow settling velocity or low effective specific gravity. If the specimens 

 contained protoplasm this mechanism would be aided. 



(2) They may have been put in suspension by wave action when they contained 

 protoplasm, and were carried to their present positions by currents. A few 

 specimens of living, shallow-water benthonic Foraminifera have been reported 

 in offshore plankton tows in the northwestern Gulf of Mexico (Phleger, 1951, 

 p. 36). 



(3) They may have been deposited by several very small-scale turbidity currents 

 which transported small amounts of sedimentary materials. 



The presence of specimens of Gumbelina in core 10 is diflicult to explain. These 

 may have been carried out by the river and deposited at their present position, or they 

 may possibly be contaminated by a salt plug bringing early Tertiary or Cretaceous 

 sediments to the surface. 



REFERENCES 



FuGLiSTER, F. C. (1947), Average monthly sea surface temperatures of the western North Atlantic 



Ocean. Papers in Phys. Oceanogr. and MeteoroL, Mass. Inst. Tech. and Woods Hole Oceanogr. 



Inst., 10 (2), 5-25. 

 Gealy, B. L. (1955), Topography of the continental slope in northwest Gulf of Mexico. Bull. Geol. 



Sac. Amer., 66, 203-228. 

 HvoRSLEV, M. J. and Stetson, H. C. (1946), Free-fall coring tube: a new type of gravity bottom 



sampler. Bidl. Geol. Soc. Amer., 57, 935-950. 

 LuDWiCK, J. C. (1950), Deep water sand layers off San Diego. Univ. of Calif, at Los Angeles, Doctor's 



Thesis. 

 Parker, F. L. (1954), Distribution of the Foraminifera in the northeastern Gulf of Mexico. Bull. 



Mus. Comp. Zool., Ill (10), 453-588. 

 Parr, A. E. (1935), Report on the hydrographic observations in the Gulf of Mexico and the adjacent 



straits made during the Yale Oceanographic Expedition on the Mabel Taylor in 1932. Bull. Bingham 



Oceanogr. Coll., 5, 1-88. 

 Phleger, F. B (1951), Ecology of Foraminifera, northwest Gulf of Mexico. Part I, Forammitcra 



distribution. Mem., Geol. Soc. Amer., 46, 1-88. 

 Phleger, F. B (1954), Foraminifera and deep-sea research. Deep-Sea Research, 2, 1-23. 

 Phleger, F. B and Parker, F. L. (1951), Ecology of Foraminifera, northwest Gulf ol Mexico. 



Part II, Foraminifera species. Mem., Geol. Soc. .Amer., 46, 1-64. 

 Phleger, F. B, Parker, F. L. and Peirson, J. F. (1953), Sediment cores from the Nort^h Atlantic 



Ocean. No. 1, North Atlantic Foraminifera. Repts. Swedish Deep-Sea E.xped., 7, 3-122. 

 Shepard, F. p. (1951), Sand and gravel in deep-water deposits. World Oil, 61-68. 

 Stetson, H. C. (1953), The sediments of the western Gulf of Mexico. Part I. The contmental terrace 



of the western Gulf of Mexico: its surface sediments, origin and development. Papers m Phys. 



Oceanogr. and MeteoroL, 12 {4), 1^5. ^. • . j- r 



Trask, p. D. (1953), The sediments of the western Gulf of Mexico. Part II, Chemical studies ot 



sediments of the western Gulf of Mexico. Papers in Phys. Oceanog. and Metrorol., 12 (4), 49-120. 



