Papers in Marine Biology and Oceanography, Suppl. to vol. 3 of Deep-Sca Research, pp. 45-57. 



Foraminiferal faunas in cores offshore from the Mississippi Delta* 



By Fred B Phleger 

 Scripps Institution of Oceanography, La Jolla 



Summary — Study of Foraminifera from fifteen cores shows presence of cold-water faunas interpreted 

 as representing glacial stages and/or substages, and of warm-water faunas interpreted as post-glacial 

 and interglacial stages and/or substages. These sequences are similar to those previously reported 

 from the northwestern Gulf of Mexico. 



The amount of post-glacial deposition is greater on the lower continental shelf and upper continental 

 slope than on the lower slope and basin. Variations in amount of post-glacial sedimentation within 

 these topographic provinces are demonstrated. 



Two cores located in the bottom of Mississippi Canyon contain faunas and sediments which have 

 been displaced downslope, presumably by turbidity currents. It is suggested that the turbidity current 

 was confined to Mississippi Canyon, and that submarine canyons generally tend to localize many 

 turbidity currents. 



INTRODUCTION 



Members of the Woods Hole Oceanographic Institution have pioneered in studies of 

 the offshore sediments in the northern Gulf of Mexico. Extensive collections of surface 

 sediments and longer cores were taken along 2,500 miles of traverses in the north- 

 western Gulf of Mexico in 1947, using the research vessel Atlantis. The physical 

 parameters of these sediments were reported and interpreted by Stetson (1953), 

 chemical studies of the materials are discussed by Trask (1953), and the foraminiferal 

 faunas are described and interpreted by Phleger (1951) and Phleger and Parker 

 (1951). In 1951 Stetson made extensive collections aboard the Atlantis in the north- 

 eastern area, from the Mississippi Delta to Florida, collecting surface sediment samples 

 and long cores along several hundred miles of traverses. The foraminiferal facies in 

 the surface sediments along these traverses have been interpreted by Parker (1954), 

 and study of the sediments is being undertaken by Stetson. 



The present paper is a study of the vertical sequences of foraminiferal faunas in 

 fifteen of these cores in a traverse extending southward from the Mississippi Delta. 

 The purposes of this study are : 



(1) To discover whether there is a vertical sequence of cold- and warm-water 

 faunas as reported from the western Gulf of Mexico and elsewhere; 



(2) To attempt to discover relative rates of deposition off a large delta; 



(3) To evaluate the role of turbidity currents in deposition in the area covered by 



the cores. 

 The cores were studied at the suggestion of Henry C. Stetson of the Woods Hole 

 Oceanographic Institution, who furnished them to the writer. The assistance of Jean 

 F. Peirson in this study is gratefully acknowledged. Dr. Rufus J. LeBlanc, of the 

 Shell Development Company, kindly arranged to have several of the cores sampled. 

 The laboratory work was supported by the Office of Naval Research (Project NR 

 081-050, Contract Nonr-233, Task 1). 



* Contribution No. 21, Marine Foraminifera Laboratory; Contribution from the Scripps Institu- 

 tion of Oceanography, New Series, No. 804. 



45 



