Diatoms in the eastern Mediterranean sapropels

Diatom assemblages preserved in extremely good condition in the sapropel S5 dated at 122127 kyr BP at Hole 971 C were analysed at ultra-high resolution in mm-order thickness based on ecological and biogeographical subdivisions of diatom species for sapropel formation. It is the only diatomaceous sapropel recovered during ODP Leg 160 in the eastern Mediterranean Sea. Diatom assemblages in laminated diatom ooze were compared with non-laminated intervals with the following results: (1) 1.3 times higher diatom abundance, in average, in terms of valve number, (2) 4.4 times higher relative abundance of oceanic species over neritic-littoral species, (3) 2.4 times higher relative abundance of mat-forming Rhizosoleniaceae over the Thalassionemataceae, and (4) lesser abundance of the various fragments of Bacteriastrium spp. and Chaetoceros resting spores. Diatom assemblages in the sapropel 35 at 1.808 myr BP at Hole 969D, which have been reported for the first time from the Mediterranean Sea, are similar to those in laminated intervals in S5 at Hole 971C but Chaetoceros resting spores are up to three times more abundant.