More than 70 dinoflagellate cyst taxa were encountered from the Pliocene-middle Miocene of Hole 1151A. The analytical results are shown as an occurrence chart in Table T1. Stratigraphic occurrences of selected dinoflagellate cyst taxa are compiled in Figure F2. Taxonomic listing of the encountered taxa is indicated in "Appendix B" and selected cysts are shown in Plate P1.
The abundance of dinoflagellate cysts relative to the total mounted residues fluctuates through the studied section (Fig. F2). The abundance peaks were observed in Sections 186-1151A-109R-3, 109R-1, and 106R-3 (lower middle Miocene), 101R-1, 100R-3, 96R-3, 95R-1, and 84R-3 (upper middle to upper Miocene), and 109R-3 and 51R-3 (lower Pliocene). In general, abundance peaks appear more frequently in the lower upper Miocene and below (i.e., approximately the lower half of the studied section).
Cyst preservation was good enough to allow identification at species level even in the lowest samples. Most specimens show no significant corrosion, although folding or slight deformation of cysts was frequent.
Most recorded species belong to gonyaulacacean genera including Cleistosphaeridium, Diphyes, Filisphaera, Hystrichokolpoma, Impagidinium, Nematosphaeropsis, Operculodinium, Pyxidinopsis, and Spiniferites. This group dominates the assemblages from the lower upper Miocene and lower section. Other groups recorded in the present study contain protoperidiniacean species including Brigantedinium, Capillicysta, Lejeunecysta, and Xandarodinium. The assemblages from the uppermost lower Pliocene through upper upper Miocene interval are particularly characterized by the frequent dominance of the protoperidiniacean taxa Brigantedinium spp. and Xandarodinium sp. A.