Vegetation Prior to and During Onset of East Antarctic Glaciation: High Resolution Palynological Insights from Sabrina Coast, East Antarctica

The Aurora Subglacial Basin (ASB) contains an estimated 3.5 m of global sea-level equivalent ice volume and is primarily drained by the Totten Glacier system, which terminates at the Sabrina Coast, East Antarctica. Thinning and retreating of the Totten Glacier indicate that this region is highly susceptible to oceanographic and atmospheric warming. The paleoclimate reconstruction of these changes, conducted in the context of this MS thesis, will improve understanding of East Antarctic Ice Sheet (EAIS) dynamics in this sensitive system. A recent study used seismic and sediment core data to document a dynamic early evolution of the EAIS in the ASB, suggesting that this large ice sheet may not be as stable as previously thought. Our study presents new high-resolution palynological data from NBP 14-02 jumbo piston cores (JPC) JPC-54 and JPC-55, which enable reconstruction of regional vegetation and environments during EAIS development. The newly described Sabrina Flora is dominated by angiosperms, with Gambierina (G.) spp. often exceeding 40% of the assemblage. Diverse Proteaceae, Battenipollis spp., Forcipites spp., Nothofagidites spp., fern and conifer palynomorphs are also notable in the assemblage. Because of pristine preservation and the frequent occurrence of Gambierina spp. clusters, the majority of the Sabrina Flora assemblage is interpreted as being penecontemporaneous with sedimentation. Biostratigraphic results indicate JPC-55 and JPC-54 are latest Paleocene and early-mid Eocene sediments (respectively) with likely contributions from reworked mid-Cretaceous marine deposits. Biomarker evidence of plant wax n-alkanoic acid yields average ẟ13C30 values of -30.2±0.5‰ (JPC-54 only), consistent with open canopy woodland or shrubby tundra. ẟD30 values were stable across JPC-54 and 55 with a mean -215±4.5‰. A fractionation of ~-100‰ indicates ẟDprecip of -128‰, slightly more positive than coastal snow in the same region today, suggesting sourcing of plant biomarkers from close to the coast. Integration of biomarker and palynological results suggests the abundance of Gambierina, Battenipollis and Proteaceae could be consistent with a drier, more open type of coastal vegetation rather than the closed rainforest vegetation often envisaged for Paleocene-Eocene Antarctica. Therefore, the Sabrina Flora provides new insight to paleoenvironment and paleoclimate reconstructions during onset of glaciation in East Antarctica