If Nothofagus was living in Antarctica during the Pliocene, then its pollen should be preserved in marine sediments around the continent. To test this hypothesis, we obtained samples from several DSDP/ODP sites that are dated as Pliocene by diatoms. Samples were collected from Sites 274, 693A, 695A, 742A, and 745B, which were selected on the basis of their proximity to the Antarctic continent and continuity of Pliocene sediments. Palynological analysis will focus on documenting the presence and relative abundance of Nothofagidites lachlaniae in these Pliocene marine sediments.
Assuming that glaciers were active during the Pliocene in some parts of Antarctica, it is possible that fossils of Nothofagidites preserved in Pliocene sediments are reworked from older deposits. Reworked palynomorphs are being deposited today by glacial processes in modern sediments around Antarctica, and previous studies have documented the relative abundance of reworked taxa, including Nothofagidites lachlaniae, in modern samples. Comparison of Pliocene and modern assemblages may provide a basis for determining whether Nothofagidites lachlaniae is reworked or not. Unusually high abundance of N. lachlaniae would favor Pliocene stands of Nothofagus as the source rather than reworking from older Cenozoic deposits.
Palynological assemblages from Site 274 samples are sparse and thus relative abundance data may be unreliable. All productive samples examined to date contain reworked palynomorphs, such as Microcachryidites antarcticus (Jurassic-Miocene) and Dilwynites tuberculatus (Paleocene-Miocene). Although not all of the samples have been examined, preliminary results indicate that Nothofagidites cf. N. lachlaniae is present in Pliocene sediments from this site. In most samples examined, Nothofagidites cf. N. lachlaniae is not unusually abundant. In sample D8135-I (Leg 28, Site 274, Core 9, Section 2, Interval 48-52 cm), which is dated at about 3 Ma by diatoms, this species accounts for most of the Nothofagidites in the assemblage. The presence and relative abundance of Nothofagidites cf. N. lachlaniae in sample D8135-I from Site 274 suggests production from Pliocene plants rather than reworking. Assemblages also contain microspores referable to the Isoëtaceae, which suggests the presence of quillworts as part of the Pliocene vegetation on Antarctica. Samples from Site 695A are currently being processed and apparently contain more abundant palynomorphs than Site 274, and may provide corroborative evidence for Nothofagus living on Antarctica during the Pliocene.