52 Fred B Phleger 



/ 



planktonic forms are treated as separate populations, with each constituting 100%. Total populations 

 are estimated for each sample, since they all contained approximately the same amount of sediment, 

 with a few exceptions. Results of the faunal analyses are on Tables II-IV. Only the more common 

 and/or important species are included in these lists; detailed analyses are on file at the Marine 

 Foraminifera Laboratory. 



Detailed faunal analyses were made on only a few samples from each core, but each sample was 

 examined to ascertain whether or not there was a faunal change. Faunas in surface sediment samples 

 from the stations along this traverse, collected with a small coring tube, have been analyzed by Parker 

 (1954). Population data from some of these samples are included for comparative purposes, since 

 the top sample from a long core may not represent the actual surface sediment due to methods of 

 collecting and processing. 



The following should be consulted for illustrations, descriptions, and additional distributions of 

 the species listed in the present report: Phleger and Parker (1951), Parker (1954), Phleger, 

 Parker and Peirson (1953), and Phleger (1954). 



CORE FAUNAS 



In a previous study of core faunas from the northwestern Gulf of Mexico (Phleger, 

 1951) it was possible to differentiate an "upper" and "lower" core fauna based 

 on the assemblages of planktonic Foraminifera. The upper planktonic fauna is the 

 modern one and has the following general composition : 



30-70% 



Globigerinoides rubra (d'Orbigny) 



10-20% 



Globigerina buUoides d'Orbigny 



G. eggeri Rhumbler 



Globorotalia truncatulinoides (d'Orbigny) 



PuUeniatina obliquiloculata (Parker and Jones) 



5-10% 



Globigerinoides sacculifera (H. B. Brady) 

 Globorotalia menardii (d'Orbigny) 



<l-5% 



Globigerinella aequilateralis (H. B. Brady) 

 Globigerinoides conglobata (H. B. Brady) 

 Globorotalia tumida (H. B. Brady) 

 Orbulina universa d'Orbigny 



The planktonic fauna which is widespread in lower sections of most northwestern 

 Gulf of Mexico cores differs in having many or all of the following species absent or 

 lower in frequency: 



Globigerina eggeri Rhumbler 



Globigerinella aequilateralis (H. B. Brady) 



Globigerinoides conglobata (H. B. Brady) 



Globorotalia menardii (d'Orbigny) 



G. truncatulinoides (d'Orbigny) 



G. tumida (H. B. Brady) 



Orbulina universa d'Orbigny 



PuUeniatina obliquiloculata (Parker and Jones) 



