Dinoflagellate cysts were recovered in 19 of the 28 samples, though some of the assemblages are very poorly preserved. Structured organic matter (STOM) or unstructured organic matter (USTOM) is present in almost all samples, and foraminiferal linings occur in most samples older than 6 Ma (Table T1). A few specimens of angiosperm pollen grains and spores were noted within the sample suite. The occurrence of the dinoflagellate cyst taxa is plotted against age in Figures F2 and F3, with the raw-count data given in Table T2.
Samples 178-1096B-3H-1, 140-142 cm, 3H-4, 140-142 cm, 20H-4, 39-41 cm, and 20H-6, 39-41 cm (14.7, 19.2, 162.6 and 165.6 mbsf, RH313 to RH316 [laboratory-assigned numbers]), and samples 178-1095B-5H-1, 108-110 cm (122.1 mbsf, RH302),-5H-4, 94-96 cm (126.4 mbsf, RH303), and 26X-7, 4-6 cm (211.9 mbsf, RH403), which dated as Pleistocene isotope Stage 7 to early Pliocene in age, proved to be virtually barren of palynomorphs but do contain USTOM and STOM together with the occasional angiosperm pollen grain and bisaccate. In contrast, Samples 178-1096C-12X-3, 141-143 cm, 33X-2, 120-122 cm, and 34X-1, 115-117 cm (302.3, 503.7, and 512.55 mbsf; RH317 to RH319), which are late to early Pliocene in age, contain assemblages of dinoflagellate cysts mostly assignable to the genera Brigantedinium, Lejeunecysta and Selenopemphix. All these fossil cyst genera have been associated with the modern genus Protoperidinium and are therefore assumed to have a heterotrophic nutritional strategy. Their occurrence within these samples indicates the presence of water with a high nutrient content.
Samples 178-1095B-9H-3, 100-102 cm, and 9H-6, 91-93 cm (163.0 and 167.4 mbsf, RH304 and RH305), dated as early Pliocene in age, contained some dinoflagellate cysts that were identified to the genus Brigantedinium. These assemblages also contained rare angiosperm pollen grains and foraminiferal linings. Unfortunately, the palynomorph assemblages do not offer any biostratigraphic information on the age of the samples. Some angiosperm pollen was observed in Sample 178-1095B-12H-1, 81-83 cm (188.3 mbsf, RH395), together with the first foraminiferal linings downcore and some evidence of reworking from Upper Cretaceous sediments. A single specimen of Brigantedinium sp. indet. was also recovered from this sample.
Samples 178-1095B-14X-1, 19-21 cm, and 14X-2, 135-137 cm (205.2 and 207.8 mbsf; RH306 and RH307), which dated as late Miocene, are almost devoid of palynomorphs, but contain USTOM, STOM, the occasional spore, and angiosperm pollen together with limited numbers of dinoflagellate cysts. The cysts present mostly occur in 178-1095B-14X-2, 135-137 cm, and consist of Brigantedinium spp. indet. and Lejeunecysta cf. communis Biffi and Grignani, 1983.
Sample 178-1095B-17X-4, 17-19 cm (238.6 mbsf, RH397), yielded a reasonable dinoflagellate cyst assemblage consisting almost entirely of Brigantedinium spp. indet. and Selenopemphix cf. nephroides Benedek, 1972, together with foraminiferal linings, pollen, and spores. The samples above and below, 178-1095B-17X-2, 119-121 cm, and 23X-1, 100-102 cm (236.7 and 292.7 mbsf, RH396 and RH398), lack dinoflagellate cysts although some pollen and spores were observed.
The remaining upper Miocene samples, except for 178-1095B-29X-1, 126-128 cm, and 34X-6, 34-35 cm (350.8 and 405.1 mbsf, RH309 and RH401), which were almost barren, contained reasonable dinoflagellate cyst assemblages, including species of Lejeunecysta and Selenopemphix that have been associated with Miocene sediments. The assemblages consist entirely of cyst taxa attributable to the Protoperidiniaceae and are therefore thought to be heterotrophic in their nutritional strategy. Dinoflagellate cysts attributable to the Gonyaulacaceae are notably absent. Foraminiferal linings, pollen, and spores are also present. The dominance of taxa derived from assumed heterotrophic dinoflagellate motile forms may again indicate the presence of water with high nutrient content sustaining a considerable diatom population (but see later discussion).