Foraminiferal faunas in cores offshore from the Mississippi Delta 55 



In core 10 from a depth of 1,298 m the following shallow-water species are important 

 constituents of the bottom core section at 144-155 cm: 



Bolivina pulchella primitiva Cushman 



B. striatula spinata Cushman 



Bulimina marginata d'Orbigny 



Buliminella cf. bassendorfensis Cushman and Parker 



Cibicidina strattoni (Applin) 



Elphidium spp. 



Nonionella opima Cushman 



" Rotalia " beccarii (Linne) variants 



Virgulina pontoni Cushman 



A few specimens of Buliminella cf. bassendorfensis also occur at 56-5-61 -5 cm and 

 2-5-7 cm. Plant fibres and fine quartz sand occur in the samples from 75 cm to 155 cm. 

 The major part of the benthonic fauna consists of species normal for the depth of the 

 core. 



Twenty-six specimens of Giimbelina are recorded from the lowermost section of 

 core 10. 



Occasional shallow-water benthonic Foraminifera are recorded from the following 

 additional deep-water cores of this series: 3, 4, 5, 6, 7, 8, 13 and 14. These are single 

 specimens and no sample contains more than four specimens, while many contain 

 none. No other evidence of displacement of sediment was observed. 



DISCUSSION 



Interpretations of the core planktonic Foraminifera in terms of " warm " (like 

 the present) and " cold " (colder than present) surface water temperatures are given 

 on Fig. 3. In this figure, " W 1 " refers to the modern warm-water fauna, *' C 1 " 

 to the last cold-water fauna, " W 2 " to the preceding warm-water fauna, etc. It is 

 suggested that these stages can be correlated in the present cores, as shown on Fig. 3, 

 especially where a succession of such faunal variations occurs and where there is no 

 indication of displaced sediment. This is especially striking in comparing cores 3, 

 4 and 6. These cores came from the same relatively small area and from similar depths 

 in the eastern Gulf of Mexico basin. Each of them has three warm-water faunas 

 separated by two cold-water ones, and these occur within approximately the same 

 thickness of sediment. 



It is suggested that these warm and cold faunas also are to be correlated with 

 similar successions described previously from northwestern Gulf of Mexico cores 

 (Phleger, 1951, Figs. 29-33). The cold-water faunas have been interpreted elsewhere 

 as representing Pleistocene glacial stages and/or substages and the warm-water faunas 

 are thus possible interglacial stages and/or substages. The widespread occurrence of a 

 cold-water fauna beneath the modern fauna in this region suggests a general coohng 

 of Gulf of Mexico surface water during the last glacial or stadial stage. 



Correlation of the planktonic faunas makes it possible to estimate the amount of 

 post-glacial sedimentation along this traverse. This is based on the assumption that 

 the upper, warm-water fauna represents post-glacial deposition. The amounts of 

 deposition appear to be approximately as follows : 



