Palynology as a Tool to Reconstruct Past Climatic Variation Recorded in Four Major Stratigraphic Intervals Sampled by the Antarctic 2006 SHALDRIL Campaign

The lack of drill cores, and thus fossil evidence, from continuous Neogene shelf and slope post-Eocene strata in the Antarctic Peninsula area has long impeded our ability to characterize the evolution of Antarctic glaciations and progressive cooling. In 2006, the SHALDRIL campaign to the Antarctic Peninsula recovered cores of in-situ shelf sediments that help constrain the region's past environmental conditions. Here we present the preliminary results from palynological analyses and paleoenvironmental evaluation of these cores. Strata from four geologic-time intervals of global-climatic significance were sampled. The NBP 06-02A 3C cores sampled the late Eocene/early Oligocene as inferred by diatom and nannofossil studies. Rich and diverse Eocene terrestrial (similar to those found in La Meseta Formation) and marine palynomorph (high abundance in Vozzhennikovia apertura) assemblages are recovered from the 3C series, providing data on late Eocene conditions in the James Ross Basin. The NBP 06-02A 12A series, dated as late Oligocene by diatom stratigraphy, is characterized by less diverse pollen assemblages, mainly composed of podocarpaceous conifer pollen, with Nothofagidites spp (fusca group), indicating colder climate on land. The fossil species of organic algae recovered from this interval (Impletosphaeridium, Micrhystridium, and leiospheres) indicate cold to polar marine environments with ice-free periods allowing production of dinoflagellates and acritarchs. The bottom of the NBP 06-02A 5D series, dated as middle Miocene by diatoms, is essentially barren of palynomorphs, with the exception of cores 5D-7 to 5D-10 that include a mix of terrestrial material, mainly Nothofagidites spp. (fusca gp.) and podocarpaceous conifer pollen, plus various angiosperm pollen and fern spores, some of which could be reworked. The upper NBP 06-02A 5D series, and the 6C and 6D dated early Pliocene are thus far barren of palynomorphs, denoting environmental conditions unsuitable for plants and dinoflagellate algal bloom at the time of deposition.