Scratching the Surface: A Marine Sediment Provenance Record From the Continental Slope of Central Wilkes Land, East Antarctica

Sian Tooze,Leanne Armand,Philip E O'Brien,Zanna Chase,Jacqueline A Halpin,Taryn L Noble

doi:10.1029/2020gc009156

Abstract

AbstractThe 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.

Highlights

The subglacial geology of Wilkes Land, East Antarctica, is poorly characterized, due to its concealment beneath 0.4–4 km of thick ice (Fretwell et al, 2013) with sparse coastal rock outcrop
We provide a brief synopsis of the East Antarctic Ice Sheet configuration from its maximum extent during the last glacial period to present, followed by a summary of the geological evolution of central Wilkes Land, East Antarctica
We report results from a marine sediment core recovered from the continental slope adjacent to Sabrina Coast of central Wilkes Land, East Antarctica, and nearby basement rocks (Figure 1 and Table S1)

Summary

Introduction

The subglacial geology of Wilkes Land, East Antarctica, is poorly characterized, due to its concealment beneath 0.4–4 km of thick ice (Fretwell et al, 2013) with sparse coastal rock outcrop. Deciphering the bedrock composition can help identify sediment erosion and transport pathways and constrain subglacial conditions (e.g., geothermal heat flow, topography, and basal erosion) deemed to have impacted Antarctic Ice Sheet evolution (Golledge et al, 2013; Jamieson et al, 2010; Lowry et al, 2020) In this context, the Sabrina Subglacial Basin in Wilkes Land (Aitken et al, 2016b; Figure 1a) is of particular interest, forming part of an extensive glacial drainage system that is predominantly situated below sea-level (Fretwell et al, 2013; Young et al, 2011). Ancient shelf sedimentary megasequences provide additional evidence of repeated ice sheet advance and retreat from the beginning of the Oligocene to the mid-Miocene (Gulick et al, 2017)

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