New Reconstructed Antarctic Palaeotopography for the Eocene-Oligocene Climate Transition
Abstract
We present the first reconstruction of the palaeotopography of the whole Antarctic continent at the Eocene-Oligocene climate transition (34 Ma). This is important because results from models to elucidate feedbacks between climate and ice sheet dynamics at this key transition have been compromised by their use of present-day topography as a boundary condition. This reconstruction of Antarctic palaeotopography at the E-O boundary restores both tectonic and erosional changes since that time. This restoration is constrained using a circum-Antarctic grid of sediment stratigraphy that enables the volume of sediment eroded since the E-O transition to be calculated. Using coring and seismic imaging data, and allowing for a biogenic component, weathering reactions and adjustments to sediment porosity, a source volume of between 5 and 13 million cubic km is thought to have been removed from an area of ca. 13 million square km. The onshore patterns of glacial landscape evolution in East Antarctica by local, regional and continental-scale ice have been estimated using an ice sheet and erosion model. The offshore material is restored to the terrestrial landscape in response to basal conditions under a range of local to continental-scale modelled ice-sheet configurations. These models can restore 3-4 million cubic km to East Antarctica. In West Antarctica, factors including the variable position of the grounding line make it impractical to use quantitative erosion models. Here our understanding of processes and patterns of erosion and deposition are combined with geological evidence for known or suspected remnants of Eocene topography in order to construct hydrologically consistent palaeo-surfaces. There are several options for geologically reasonable surfaces that imply 5-10 million cubic km of eroded volume. Uncertainties in eroded volume are muted by the transformation to palaeo-elevation because isostatic compensation generally limits the change in average regional elevation to 15-20% of the thickness eroded. Given the uncertainties in sediment volume, we present a ‘maximum’ and a ‘minimum’ topographic reconstruction at resolutions of 10 km. This allows future model experiments to test for model sensitivity to palaeotopography as well as for their use of the best possible reconstruction based on current knowledge.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFMPP13B1526B
- Keywords:
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- 0473 BIOGEOSCIENCES / Paleoclimatology and paleoceanography;
- 0798 CRYOSPHERE / Modeling;
- 9310 GEOGRAPHIC LOCATION / Antarctica;
- 9604 INFORMATION RELATED TO GEOLOGIC TIME / Cenozoic