Distribution of planktonic Foraminifera in some Mediterranean sediments 209 



The third assemblage is found in the Aegean Sea. It differs from that of the eastern 

 Mediterranean in the following ways : 



Eastern Mediterranean Aegean Sea 



Globigerina eggeri 2-13% (except 2 3-28% (mostly more than 



stas. off Israel) 20%) 



G. pachyderma slight consistent increase 



Globigerinoides saccuUfera 3-14% 0-3% 



In the western Med'terranean the population must be adapted to a wider tempera- 

 ture range than that found in the adjacent Atlantic. The winter temperatures are more 

 nearly analogous to those found on the western Atlantic continental slope in mid- 

 latitudes. In some respects the western Mediterranean population reflects this and 

 shows a resemblance to the populations in that area (Parker, 1948; Phleger, 1939, 

 1942) as shown by the high frequencies of Globigerina bulloides and G. inflata and the 

 low frequency of Globigerinoides saccuUfera as well as in lesser respects. The fauna 

 occurring at the three stations (4732-4734) just east of Gibraltar is of interest. Two 

 of these stations lie within the low temperature area reported by Rough (1940). 

 Here exceptionally high frequencies of Globigerina bulloides and low frequencies of 

 Globigerinoides rubra and Globorotalia truncatulinoides are found. Whether or not 

 these changes are due to a lowered mean temperature maximum is a matter of specula- 

 tion. The presence of G. hirsuta in significant frequencies in this area may be due to 

 transport by the entering Atlantic current. The faunas reported by Muraour ( 1954 

 A, b) from the vicinity of Algiers show a much lower percentage of Globigerinoides 

 rubra. The populations reported by Phleger (1947) from the Tyrrhenian Sea are 

 analogous to those found in the present study. 



The increase in the mean minimum temperature in the eastern area from 13^ C 

 to 16° C may account for some or all of the shifts in population found there, as similar 

 trends occur when passing from mid to low latitudes in the Atlantic. In general there 

 is a decrease in such species as Globigerina bulloides and G. inflata, which occur in 

 high frequencies in mid-latitudes, and an increase in Globigerinoides saccuUfera 

 which is found in increasingly high frequencies in low latitudes. 



In the Aegean Sea the mean minimum temperature is 13° C, as it is in the western 

 Mediterranean, which may account for the more consistent occurrence of Globigerina 

 pachyderma and the decrease in Globigerinoides saccuUfera as compared to eastern 

 area occurrences. Lower salinities in the northern part and/or changes in the chemistry 

 of the surface water resulting from the inflow of water from the Black Sea may also 

 account for these changes. This may be especially true in the case of the high fre- 

 quencies of Globigerina eggeri and the fact that many of the specimens are atypical. 



The populations at several stations, besides those noted previously, show unusual 

 features but two are especially noteworthy. Station 4724A contains what appears to 

 be a " colder water " fauna. There are higher frequencies of Globigerina eggeri, 

 G. pachyderma, and G. quinqueloba and lower frequencies ofGlobigerinella aequilatcralis 

 and Globigerinoides rubra. Globigerina eggeri is the only species of the group which 

 does not fit this pattern, since that species is found in higher frequencies m low 

 latitudes Further study may reveal whether or not this fauna is pre-modern. The 

 sample from station 4718 contains a large percentage of weathered, discoloured 



