Abstract
Marine diatoms in tillites along the Transantarctic Mountains (TAMs) have been used to suggest a diminished East Antarctic Ice Sheet (EAIS) during Pliocene warm periods. Updated ice-sheet modelling shows significant Pliocene EAIS retreat, creating marine embayments into the Wilkes and Aurora basins that were conducive to high diatom productivity and rapid accumulation of diatomaceous sediments. Here we show that subsequent isostatic uplift exposed accumulated unconsolidated marine deposits to wind erosion. We report new atmospheric modelling utilizing Pliocene climate and derived Antarctic landscapes indicating that prevailing mid-altitude winds transported diatoms towards the TAMs, dominantly from extensive emerged coastal deposits of the Aurora Basin. This result unifies leading ideas from competing sides of a contentious debate about the origin of the diatoms in the TAMs and their link to EAIS history, supporting the view that parts of the EAIS are vulnerable to relatively modest warming, with possible implications for future sea-level rise.
Highlights
Marine diatoms in tillites along the Transantarctic Mountains (TAMs) have been used to suggest a diminished East Antarctic Ice Sheet (EAIS) during Pliocene warm periods
Past EAIS variability has been a matter of debate and speculation since the publication of a series of strongly contrasting papers that followed a controversial report by Webb et al.[10] that inferred major EAIS retreat along the Wilkes, Aurora and Pensacola subglacial basins of East Antarctica during earlyand mid-Pliocene warm intervals, based on marine diatoms extracted from tillites in the Transantarctic Mountains (TAMs)
We evaluate coastal isostatic response over a Pliocene Antarctic ice-sheet reconstruction derived from an icesheet model that incorporates ice-sheet grounding zone processes, including cliff failure and hydrofracturing[7], simulate wind regimes under these Pliocene landscape conditions using a regional climate model (RCM)[41] to address the long-standing debate regarding the interpretation of Pliocene-age marine diatoms recovered from Sirius Group glacial deposits in the TAMs5
Summary
Marine diatoms in tillites along the Transantarctic Mountains (TAMs) have been used to suggest a diminished East Antarctic Ice Sheet (EAIS) during Pliocene warm periods. Past EAIS variability has been a matter of debate and speculation since the publication of a series of strongly contrasting papers that followed a controversial report by Webb et al.[10] that inferred major EAIS retreat along the Wilkes, Aurora and Pensacola subglacial basins of East Antarctica during earlyand mid-Pliocene warm intervals, based on marine diatoms extracted from tillites in the Transantarctic Mountains (TAMs) These tillite units are collectively referred to as the Sirius Group, or Sirius Formation in older literature. Subsequent ice-sheet advance was suggested to have eroded and transported diatomaceous sediments to the TAMs, forming Sirius Group tills This hypothesis implied dramatic EAIS retreat deep into the interior of the East Antarctic subglacial basins during the Pliocene, but significant post-Pliocene mountain uplift or postretreat ice-sheet configurations much larger than have otherwise been hypothesized. Subglacial transport of the diatoms as described by Harwood and Webb[15] may be further called into question by results of a ring-shear experiment[25] that documented high rates of diatom fragmentation in till subjected to shear strains typical of wet-based subglacial deformation, diatoms and diatom clasts can be transported great distances if frozen in glacier ice, whether resulting from aeolian deposition onto snow/ice surfaces or as debris frozen in basal ice
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