Constraining the amplitude of late Oligocene bathymetric changes in Western Ross Sea during orbitally-induced oscillations in the East Antarctic Ice Sheet: (1) Implications for glacimarine sequence stratigraphic models

Authors

Gavin B. Dunbar, University of Wellington, New ZealandFollow
T. R. Naish, University of Wellington, New Zealand
Peter J. Barrett, University of Wellington, New ZealandFollow
Christopher R. Fielding, University of Nebraska-LincolnFollow
R. D. Powell, Northern Illinois UniversityFollow

Date of this Version

4-2008

Comments

Published in Palaeogeography, Palaeoclimatology, Palaeoecology 260:1-2 (April 7, 2008), pp. 50–65 (Special issue on Antarctic cryosphere and Southern Ocean climate evolution (Cenozoic-Holocene), from 1) EGU Meeting, and 2) XXIX SCAR Meeting); doi:10.1016/j.palaeo.2007.08.018 Copyright © 2007 Elsevier B.V. Used by permission.

Abstract

Abstract Late Oligocene shallow glacimarine sequences recovered from western Ross Sea, Antarctica by the Cape Roberts (drilling) Project display orbitally-influenced cycles of advance and retreat of a laterally-extensive ice sheet across the continental shelf, in concert with changes in contemporary water-depth. During interglacial periods, when the glacier terminated on land, the coastline was largely ice-free and wave-influenced, and sediments accumulated in hydrodynamic equilibrium with the contemporary wave-climate. Here, we present estimates of paleobathymetry from intervals of three Milankovitch-duration glacimarine sequences (9, 10 and 11) that accumulated in open ocean conditions. We utilize an approach where the percentage of mud (< 63 μm fraction) in bulk sediment is related to the wave-induced bed shear stress, and for a given wave climate, water depth (e.g. Dunbar, G. B. and Barrett, P. J., 2005. Estimating paleobathymetry of wave-graded continental shelves from sediment texture. Sedimentology 52, 253–269.). Particle size-derived changes in paleobathymetry for the three late Oligocene sequences were between 20–40 and 60–90 m. These water depth changes are consistent with the magnitude of contemporary global eustatic sea-level changes of 30–40 m estimated from far-field continental margin and deep-marine ocean proxy records. On the basis of our bathymetric constraints we contribute to a conceptual stratigraphic model for shallow glacimarine sequences, whose depositional architecture is controlled by a combination glacier advance and retreat and changes in relative sea-level.