ALBERT

Description: The subglacial geology in Wilkes Land, East Antarctica is masked by thick ice and remains largely unexplored. Yet the underlying crustal architecture records evidence of repeated supercontinent cycles and provides the geological template for the evolution of the Antarctic Ice Sheet. Sediment eroded from under the ice is ultimately deposited in the ocean, such that marine sediment can be used to characterise the adjacent subglacial geology. We use detrital grain morphology, geochemistry and isotopic data from a kasten core to construct a new marine sediment provenance record for the continental slope of central Wilkes Land, and provide new isotopic signatures from proximal coastal outcrops for comparison. We establish the source rock type, age and provenance, and the associated transport pathways and mechanisms responsible for detrital sediment input from 23.5 ka to present. A principally igneous source is revealed with dominant age populations between c. 1200-1100 Ma and c. 1600-1300 Ma, characteristic of the proximal Banzare, Nuyina and Wilkes Provinces. The detrital geochronology suggests no change in sediment provenance over the last 23.5 ka, despite major ice sheet retreat during this time. A minor c. 700-500 Ma detrital age population unknown from the central Wilkes region was likely transported westward via icebergs to the core site. These findings broadly correspond with earlier interpretations of the subglacial geology and erosion rates at the base of the ice sheet predicted from two ice sheet models, demonstrating the value of sediment provenance studies for uncovering proximal subglacial geology and reconstructing past ice sheet configurations.

Description: Downcore measurements of iceberg-rafted debris (IBRD) flux and biogenic silica concentrations in kasten core IN2017_V01-A042-KC14 from the continental slope of central Wilkes Land, East Antarctica. The IBRD flux was calculated by multiplying the coarse sand fraction by the linear sedimentation rate and the dry bulk density at each depth interval along the core. All of these values are shown. The biogenic silica concentration is shown as a percentage.

Description: Pb-Pb ratios, ages and trace element data from detrital feldspars in kasten core IN2017_V01-A042-KC14 from the continental slope of central Wilkes Land, East Antarctica and in-situ feldspars from coastal basement rocks in East Antarctica (Chick Island and Balaena Islets). All data was obtained using laser ablation-inductively-couple plasma mass spectrometry (LA-ICPMS). All ratios and ages are shown with one standard error.

Description: The Antarctic continental slope spans the depths from the shelf break (usually between 500 and 1000 m) to ~3000 m, is very steep, overlain by 'warm' (2-2.5 °C) Circumpolar Deep Water (CDW), and life there is poorly studied. This study investigates whether life on Antarctica's continental slope is essentially an extension of the shelf or the abyssal fauna, a transition zone between these or clearly distinct in its own right. Using data from several cruises to the Weddell Sea and Scotia Sea, including the ANDEEP (ANtarctic benthic DEEP-sea biodiversity, colonisation history and recent community patterns) I-III, BIOPEARL (Biodiversity, Phylogeny, Evolution and Adaptive Radiation of Life in Antarctica) 1 and EASIZ (Ecology of the Antarctic Sea Ice Zone) II cruises as well as current databases (SOMBASE, SCAR-MarBIN), four different taxa were selected (i.e. cheilostome bryozoans, isopod and ostracod crustaceans and echinoid echinoderms) and two areas, the Weddell Sea and the Scotia Sea, to examine faunal composition, richness and affinities. The answer has important ramifications to the link between physical oceanography and ecology, and the potential of the slope to act as a refuge and resupply zone to the shelf during glaciations. Benthic samples were collected using Agassiz trawl, epibenthic sledge and Rauschert sled. By bathymetric definition, these data suggest that despite eurybathy in some of the groups examined and apparent similarity of physical conditions in the Antarctic, the shelf, slope and abyssal faunas were clearly separated in the Weddell Sea. However, no such separation of faunas was apparent in the Scotia Sea (except in echinoids). Using a geomorphological definition of the slope, shelf-slope-abyss similarity only changed significantly in the bryozoans. Our results did not support the presence of a homogenous and unique Antarctic slope fauna despite a high number of species being restricted to the slope. However, it remains the case that there may be a unique Antarctic slope fauna, but the paucity of our samples could not demonstrate this in the Scotia Sea. It is very likely that various ecological and evolutionary factors (such as topography, water-mass and sediment characteristics, input of particulate organic carbon (POC) and glaciological history) drive slope distinctness. Isopods showed greatest species richness at slope depths, whereas bryozoans and ostracods were more speciose at shelf depths; however, significance varied across Weddell Sea and Scotia Sea and depending on bathymetric vs. geomorphological definitions. Whilst the slope may harbour some source populations for localised shelf recolonisation, the absence of many shelf species, genera and even families (in a poorly dispersing taxon) from the continental slope indicate that it was not a universal refuge for Antarctic shelf fauna.