Scratching the Surface: A Marine Sediment Provenance Record From the Continental Slope of Central Wilkes Land, East Antarctica. (1st November 2020)

• Record Type: Journal Article
• Authors: Tooze, Sian; Halpin, Jacqueline A.; Noble, Taryn L.; Chase, Zanna; O'Brien, Philip E.; Armand, Leanne
• Is Part Of: Geochemistry, geophysics, geosystems. Volume 21:Number 11(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-11-01
• Subjects: Antarctic geology -- East Antarctica -- geochemistry -- geochronology -- sediment provenance -- Wilkes Land; Geochemistry -- Periodicals; Geophysics -- Periodicals; Earth sciences -- Periodicals; 550.5
• DOI: 10.1029/2020GC009156
• Languages: English
• ISSNs: 1525-2027

Abstract

Abstract: The geology of Wilkes Land, East Antarctica, is masked by kilometers of ice and remains largely unexplored. Defining the sediment provenance adjacent to this hidden region is important for distinguishing the proximal subglacial basement terranes and refining the dynamic regional glaciological history. This study presents a detrital sediment provenance record spanning c. 23.5 ka from the continental slope of central Wilkes Land. Sediment provenance was characterized using U‐Pb geochronology and trace element geochemistry from detrital zircon, titanite and apatite, and Pb isotopic signatures from detrital feldspar. These data were compared with new feldspar Pb‐isotopic signatures and existing U‐Pb zircon data sets from rare nearby coastal outcrop. A principally igneous source was revealed with dominant age populations between c. 1, 360‐1, 100 Ma and c. 1, 620‐1, 490 Ma, characteristic of rocks of the proximal Wilkes and Banzare provinces, respectively. Minor detritus was additionally sourced from the proximal Nuyina Province (c. 1, 450‐1, 390 Ma). Temporal variation in the climate and ice sheet configuration are likely responsible for subtle downcore changes observed in detrital sediment provenance. High sedimentation rates during the glacial period suggest reworking of continental shelf sediments and downslope transport in debris flows during ice sheet advance. Glacial meltwater fluxes fed largely by the Totten Glacier were responsible for supplying detritus during deglaciation. During interglacials, detritus was derived from a broad coastal region and delivered to the slope via multiple glacial outlets. These results present the first substantial offshore evidence to support recent interpretations that the subglacial crust of central Wilkes Land has a dominantly Mesoproterozoic history. Plain Language Summary: The geology underlying the Antarctic ice cap is poorly known due to thick and extensive ice cover. Understanding the composition of the rock types beneath the ice and how they are eroded and transported to the ocean is important for establishing the regional glaciological and tectonic histories. This study analyzes the age and composition of grains in marine sediment originally eroded from Wilkes Land, East Antarctica, to determine the source rock type, age, and likely provenance region. The composition of detritus is compared to that of nearby coastal rocks and the geology of southern Australia that was once adjacent to East Antarctica during past supercontinents. The detrital composition and age signature match the proximal Banzare, Nuyina, and Wilkes provinces in East Antarctica, validating the use of marine sediment records as a window into the hidden Antarctic bedrock. During glacial periods, detritus was scoured from the continental shelf and redeposited downslope. As the ice sheet began to retreat, fluxes of sediment‐laden meltwater were largely supplied by Totten Glacier. Detritus is sourced from a broad region of the coast during warm interglacials. This record provides the first substantial physical evidence to support former interpretations of the subglacial terrain in central Wilkes Land. Key Points: Multitracer provenance study offshore central Wilkes Land, East Antarctica, supports former interpretations of the subglacial geology Age and composition of the detritus matches basement rocks of the proximal onshore Wilkes, Nuyina, and Banzare provinces Changes in detrital sediment provenance over c. 23.5 ka are associated with variation in climate and ice sheet configuration