ALBERT

Description: A total of 35 samples from the late-middle Eocene to earliest Oligocene (643.73-520.88 mbsf) were analysed for their pollen and spore content. Slides were analysed using a Leica DM500 and Leica DM2000 transmitted light microscopes at 200x and 1000x magnification. Where possible, counts of 300 (excluding reworked grains) sporomorphs were made. Only samples containing 50 or more in situ sporomorphs were used for further analysis and evaluation. Sporomorph diversity was measured using both the Shannon–Wiener index and the observed number of taxa. A rarefaction method for sums of ≥50 and ≥100 grains was applied, so that the effect caused by differences in the sample size may be removed allowing the estimation of the number of sporomorph species at a constant sample size. Detrended Correspondence Analysis (DCA) was performed, with downweighting of rare species by removing pollen types whose representation is 〈5%. Estimates for terrestrial mean annual temperature (MAT), mean annual precipitation (MAP), warmest month mean temperature (WMMT) and coldest month mean temperature (CMMT) were obtained using the NLR approach in conjunction with the Probability Density Function (PDF) method.

Description: Concentrations of isoGDGTs and brGDGTs, All samples and corresponding depths, ages, lithology (* = generally greener intervals or very small intervals with laminations that were not incorporated into the log of Salabarnada et al., 2018), method used, isoprenoid and branched GDGT integrated values, TEX86, BIT, Methane Index (MI), GDGT-2/Crenarchaeol ratios GDGT-0/Crenarchaeol ratios and GDGT-2/GDGT-3 ratios, and #rings-tetra values. Discarded samples are indicated in the Outlier column. Discards based on BIT and #rings-tetra are indicated with an 'a'. Discarded samples with GDGT-0/Crenarchaeol ratio above 2.0 are indicated with a 'b', those with MI values above 0.3 are indicated with a 'c', those with GDGT-2/crenarchaeol ratios above 0.4 with 'd' and those with ΔRI value above 0.6 with an 'O'. Discarded samples taken from mass waste deposits are underlined.Note that data from mass waste deposits are included in this dataset, but may have to be discarded.

Description: The early Eocene epoch was characterized by extreme global warmth, which in terrestrial settings was characterized by an expansion of near-tropical vegetation belts into the high latitudes. During the middle to late Eocene, global cooling caused the retreat of tropical vegetation to lower latitudes. In high-latitude settings, near-tropical vegetation was replaced by temperate floras. This floral change has recently been traced as far south as Antarctica, where along the Wilkes Land margin paratropical forests thrived during the early Eocene and temperate Nothofagus forests developed during the middle Eocene. Here we provide both qualitative and quantitative palynological data for this floral turnover based on a sporomorph record recovered at Integrated Ocean Drilling Program (IODP) Site U1356 off the Wilkes Land margin. Following the nearest living relative concept and based on a comparison with modern vegetation types, we examine the structure and diversity patterns of the Eocene vegetation along the Wilkes Land margin. Our results indicate that the early Eocene forests along the Wilkes Land margin were characterized by a diverse canopy composed of plants that today occur in tropical settings; their richness pattern was similar to that of present-day forests from New Caledonia. The middle Eocene forests were characterized by a canopy dominated by Nothofagus and exhibited richness patterns similar to modern Nothofagus forests from New Zealand.

Description: The warmest global climates of the past 65 million years occurred during the early Eocene epoch (about 55 to 48 million years ago), when the Equator-to-pole temperature gradients were much smaller than today (doi:10.1130/0091-7613(1995)023〈1044:ECCALT〉2.3.CO;2, doi:10.1038/nature08399) and atmospheric carbon dioxide levels were in excess of one thousand parts per million by volume (doi:10.1016/j.gca.2003.09.002, doi:10.1038/ngeo1186). Recently the early Eocene has received considerable interest because it may provide insight into the response of Earth's climate and biosphere to the high atmospheric carbon dioxide levels that are expected in the near future (doi:10.1007/s10584-011-0156-z) as a consequence of unabated anthropogenic carbon emissions (doi:10.1038/ngeo1186, doi:10.1038/nature06588). Climatic conditions of the early Eocene 'greenhouse world', however, are poorly constrained in critical regions, particularly Antarctica. Here we present a well-dated record of early Eocene climate on Antarctica from an ocean sediment core recovered off the Wilkes Land coast of East Antarctica. The information from biotic climate proxies (pollen and spores) and independent organic geochemical climate proxies (indices based on branched tetraether lipids) yields quantitative, seasonal temperature reconstructions for the early Eocene greenhouse world on Antarctica. We show that the climate in lowland settings along the Wilkes Land coast (at a palaeolatitude of about 70° south) supported the growth of highly diverse, near-tropical forests characterized by mesothermal to megathermal floral elements including palms and Bombacoideae. Notably, winters were extremely mild (warmer than 10 °C) and essentially frost-free despite polar darkness, which provides a critical new constraint for the validation of climate models and for understanding the response of high-latitude terrestrial ecosystems to increased carbon dioxide forcing.

Description: Detailed, stratigraphically well-constrained environmental reconstructions are available for Paleocene and Eocene strata at a range of sites in the southwest Pacific Ocean (New Zealand and East Tasman Plateau; ETP) and Integrated Ocean Discovery Program (IODP) Site U1356 in the south of the Australo-Antarctic Gulf (AAG). These reconstructions have revealed a large discrepancy between temperature proxy data and climate models in this region, suggesting a crucial error in model, proxy data or both. To resolve the origin of this discrepancy, detailed reconstructions are needed from both sides of the Tasmanian Gateway. Paleocene-Eocene sedimentary archives from the west of the Tasmanian Gateway have unfortunately remained scarce (only IODP Site U1356), and no well-dated successions are available for the northern sector of the AAG. Here we present new stratigraphic data for upper Paleocene and lower Eocene strata from the Otway Basin, southeast Australia, on the (north)west side of the Tasmanian Gateway. We analyzed sediments recovered from exploration drilling (Latrobe-1 drill core) and outcrop sampling (Point Margaret) and performed high-resolution carbon isotope geochemistry of bulk organic matter and dinoflagellate cyst (dinocyst) and pollen biostratigraphy on sediments from the regional lithostratigraphic units, including the Pebble Point Formation, Pember Mudstone and Dilwyn Formation. Pollen and dinocyst assemblages are assigned to previously established Australian pollen and dinocyst zonations and tied to available zonations for the SW Pacific. Based on our dinocyst stratigraphy and previously published planktic foraminifer biostratigraphy, the Pebble Point Formation at Point Margaret is dated to the latest Paleocene. The globally synchronous negative carbon isotope excursion that marks the Paleocene-Eocene boundary is identified within the top part of the Pember Mudstone in the Latrobe-1 borehole and at Point Margaret. However, the high abundances of the dinocyst Apectodinium prior to this negative carbon isotope excursion prohibit a direct correlation of this regional bio-event with the quasi-global Apectodinium acme at the Paleocene-Eocene Thermal Maximum (PETM; 56 Ma). Therefore, the first occurrence of the pollen species Spinizonocolpites prominatus and the dinocyst species Florentinia reichartii are here designated as regional markers for the PETM. In the Latrobe-1 drill core, dinocyst biostratigraphy further indicates that the early Eocene (~56-51 Ma) sediments are truncated by a ~10 Myr long hiatus overlain by middle Eocene (~40 Ma) strata. These sedimentary archives from southeast Australia may prove key in resolving the model-data discrepancy in this region, and the new stratigraphic data presented here allow for detailed comparisons between paleoclimate records on both sides of the Tasmanian Gateway.

Description: Global climate cooled from the early Eocene hothouse (~52-50 Ma) to the latest Eocene (~34 Ma). At the same time, the tectonic evolution of the Southern Ocean was characterized by the opening and deepening of circum-Antarctic gateways, which affected both surface- and deep-ocean circulation. The Tasmanian Gateway played a key role in regulating ocean throughflow between Australia and Antarctica. Southern Ocean surface currents through and around the Tasmanian Gateway have left recognizable tracers in the spatiotemporal distribution of plankton fossils, including organic-walled dinoflagellate cysts. This spatiotemporal distribution depends on both the physico-chemical properties of the water masses and the path of surface-ocean currents. The extent to which climate and tectonics have influenced the distribution and composition of surface currents and thus fossil assemblages has, however, remained unclear. In particular, the contribution of climate change to oceanographic changes, superimposed on long-term and gradual changes induced by tectonics, is still poorly understood. To disentangle the effects of tectonism and climate in the southwest Pacific Ocean, we target a climatic deviation from the long-term Eocene cooling trend, the Middle Eocene Climatic Optimum (MECO; ~40 Ma). This 500-thousand-year-long phase of global warming was unrelated to regional tectonism, and thus provides a test case to investigate the ocean's physiochemical response to climate change alone. We reconstruct changes in surface-water circulation and temperature in and around the Tasmanian Gateway during the MECO through new palynological and organic geochemical records from the central Tasmanian Gateway (Ocean Drilling Program Site 1170), the Otway Basin (southeastern Australia) and the Hampden Beach section (New Zealand). Our results confirm that dinocyst communities track specific surface-ocean currents, yet the variability within the communities can be driven by superimposed temperature change. Together with published results from the east of the Tasmanian Gateway, our new results suggest a shift in surface-ocean circulation during the peak of MECO warmth. Simultaneous with high sea-surface temperatures in the Tasmanian Gateway area, pollen assemblages indicate warm temperate rainforests with paratropical elements along the southeastern margin of Australia. Finally, based on new age constraints we suggest that a regional southeast Australian transgression might have been coincident with the MECO.

Description: Palynology data and analysis for branched glycerol dialkyl glycerol tetraethers (brGDGTs) from Point Margaret (Southern Australia), respectively, were used to estimate the mean annual air temparature during the Paleocene-Eocene Thermal Maximum.