ALBERT

Description: Improvements in our capability to reconstruct ancient surface-ocean conditions based on organic-walled dinoflagellate cyst (dinocyst) assemblages from the Southern Ocean provide an opportunity to better establish past position, strength and oceanography of the subtropical front (STF). Here, we aim to reconstruct the late Eocene to early Miocene (37–20 Ma) depositional and palaeoceanographic history of the STF in the context of the evolving Tasmanian Gateway as well as the potential influence of Antarctic circumpolar flow and intense waxing and waning of ice. We approach this by combining information from seismic lines (revisiting existing data and generating new marine palynological data from Ocean Drilling Program (ODP) Hole 1168A) in the western Tasmanian continental slope. We apply improved taxonomic insights and palaeoecological models to reconstruct the sea surface palaeoenvironmental evolution. Late Eocene–early Oligocene (37–30.5 Ma) assemblages show a progressive transition from dominant terrestrial palynomorphs and inner-neritic dinocyst taxa as well as cysts produced by heterotrophic dinoflagellates to predominantly outer-neritic/oceanic autotrophic taxa. This transition reflects the progressive deepening of the western Tasmanian continental margin, an interpretation supported by our new seismic investigations. The dominance of autotrophic species like Spiniferites spp. and Operculodinium spp. reflects relatively oligotrophic conditions, like those of regions north of the modern-day STF. The increased abundance in the earliest Miocene of Nematosphaeropsis labyrinthus, typical for modern subantarctic zone (frontal) conditions, indicates a cooling and/or closer proximity of the STF to the site . The absence of major shifts in dinocyst assemblages contrasts with other records in the region and suggests that small changes in surface oceanographic conditions occurred during the Oligocene. Despite the relatively southerly (63–55∘ S) location of Site 1168, the rather stable oceanographic conditions reflect the continued influence of the proto-Leeuwin Current along the southern Australian coast as Australia continued to drift northward. The relatively “warm” dinocyst assemblages at ODP Site 1168, compared with the cold assemblages at Antarctic Integrated Ocean Drilling Program (IODP) Site U1356, testify to the establishment of a pronounced latitudinal temperature gradient in the Oligocene Southern Ocean.

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 Knapps Narrows core was drilled at 38.72129N, -76.33162W on the Eastern Shore of Maryland. The cored target interval lies between 84-102 meters in the Nanjemoy Formation. Calcareous nannofossil biozonation was established in conjunction with paleomagnetic data, allowing us to date the interval to approximately 53.7 mya. Benthic foraminiferal and bulk carbon isotope data allowed for further refinement of the dating of this interval, allowing us to identify ETM2 and H2 on the basis of carbon isotope stratigraphy. For analyses of benthic foraminifera 4-6 Anomalinoides acutus specimens were picked from the 180-250 μm size fraction at each interval. Dinoflagellate cyst assemblages were counted in order to allow for paleo-environmental analysis. Benthic foraminiferal δ18O and TEX86 temperature proxies were compiled over the interval of interest. Semi-quantitative clay mineral assemblages were used to test for changes in the weathering response over hyperthermal intervals. There is excellent agreement between the δ18O and TEX86 temperature proxies, although the highest temperatures do not correspond to either hyperthermal event. There is a noticeable increase in illite content during the ETM2 interval, and an absence of kaolinite. Dinoflagellate assemblages suggest changes in marine paleo-environmental conditions were driven by long-term trends rather than immediate responses to the hyperthermal events.