THE RECORD OF GARNETS AND DICTYOCORYNE (PROFUNDA?) AT SITES TN057-6-PC4 AND ODP 177-1090 (AGULHAS RIDGE, SOUTH ATLANTIC)
A second notable feature of the studied interval is the presence of the radiolarian Dictyocoryne (profunda?) during the warmest intervals only. So far, MIS 9-14 at ODP 177-1090 and MIS 5c, 10-12 at TN057-6-PC4 have been counted. D. profunda has been considered to be a warm-water indicator (Casey, 1971), although specimens have been found in cores from more southerly latitudes (Brathauer, 1996). However, in that study all sizes from >40 microns up were counted, while we studied only the size interval from 250 microns to 2 mm. Matsuoka and Anderson (1992) and Sugiyama and Anderson (1997) investigated the effects of silica, salinity and temperature on growth and survival of the closely-related D. truncatum, and established that temperature is the critical variable affecting growth. It is possible that the pattern of occurrence of D. (profunda?) that we observe reflects a similar effect of temperature on size. If the pattern persists in our cores, this idea should be further investigated.