Phytoliths are absent to rare in all samples, with a maximum of 12 specimens observed at 329.13 mbsf (Table T1). Spherical phytoliths are the most common, composing 89% of the overall assemblage. Phytoliths are most common between 291.28 and 601.48 mbsf (lower-middle Miocene). Overall, discounting the probable contaminants, 91% (47 specimens) are comparable to forms produced in modern trees/shrubs, 7% (4 specimens) grass, and 2% (1 specimen) fern. The low abundances and lack of specific current knowledge of phytolith production in modern plants does not allow any significant interpretation of source vegetation composition. At and below 692.48 mbsf, only irregular blocks and plates of biogenic silica of unknown natural origin are present in the residues, with the exception of a single verrucose spherical specimen considered a contaminant. Other siliceous microfossils including diatoms (Chaetoceros? spores and frustules), chrysophycean cysts, Parmales, radiolarians, silicified terrestrial palynomorphs, silicoflagellates, sponge spicules, and possible testate amoeba plates are present throughout but become rare, fragmented, and poorly preserved at and below 692.48 mbsf. In the lowermost, virtually barren samples at and below this level, flakes of low-relief, highly variable in outline, isotropic silica dominate the residues and appear to have replaced the structured biogenic silica. These observations are consistent with a diagenetic transition from amorphous opal-A to opal-CT, identified by downhole temperature measurements to theoretically occur at ~600 mbsf (O'Brien, Cooper, Richter, et al., 2001).
Direct comparison with the terrestrial palynomorph record from Site 1165 is not possible because of the low phytolith abundances and lack of knowledge about production of comparable phytolith forms in modern plants. The terrestrial palynomorph assemblage does contain Nothofagidites spp. pollen (Macphail and Truswell, "Palynology of Neogene Slope and Rise Deposits from ODP Sites 1165 and 1167, East Antarctica," this volume), however, which is consistent with one possible natural origin of the smooth and verrucose spherical phytoliths. Macphail and Truswell ("Palynology of Neogene Slope and Rise Deposits from ODP Sites 1165 and 1167, East Antarctica," this volume) also note that the occurrence of Poaceae pollen in the terrestrial palynology preparations could be due to modern contamination during drilling operations.
Phytoliths are absent to rare in all samples with a maximum of just six specimens in the uppermost sample (Table T1). Spherical phytoliths are again most common, composing five of the ten specimens observed. Overall, six specimens are comparable to forms produced by modern trees/shrubs, three cubic forms of unknown origin, and one probable grass contaminant. At and below 38.61 mbsf, the samples are predominantly barren with a total of four phytoliths observed (one considered a contaminant), and rare, poorly preserved fragments of the other siliceous microfossil groups are noted. These virtually barren samples are dominated by silica flakes similar to those observed in the lower part of the hole at Site 1165. Siliceous microfossils reappear in two samples at 142.32 and 148.11 mbsf, but no phytoliths are observed.
Lithostratigraphic Unit III (156.62-267.17 mbsf) has the greatest potential for phytolith occurrence, containing organic-rich material and some wood, and is interpreted as possibly representing deposition on a preglacial alluvial plain or braided delta of a glacial outwash system (O'Brien, Cooper, Richter, et al., 2001). Samples from Unit III were not supplied by the core repository; however, it is envisaged that phytolith recovery from this interval would be poor with reference to the samples processed at and below 142.32 mbsf that are barren of phytoliths.
Comparison with the terrestrial palynomorph record for Site 1166 (Macphail and Truswell, "Palynology of Site 1166, Prydz Bay, East Antarctica," this volume) is not possible because of the lack of current knowledge about the natural origin of pellet sphericals, anticlinal epidermal, and cubic phytoliths.