- 1Department of Geosciences, Swedish Museum of Natural History, Stockholm, Sweden (chris.mark@nrm.se)
- 2Institute for Geology and Palaeontology, University of Münster, 48149 Münster, Germany (roland.neofitu@uni-muenster.de)
- 3Department of Earth Sciences, University of Gothenburg, 413 20 Gothenburg, Sweden
- 4Scottish Universities Environmental Research Centre, East Kilbride G75 0QF, United Kingdom
- 5CASP, West Building, Madingley Rise, Madingley Road, Cambridge CB3 0UD, United Kingdom
- 6Department of Earth and Environmental Sciences, Wesleyan University, Middletown, CT 06459, USA
- 7UCD School of Earth Sciences, University College Dublin, Belfield, Dublin D04 V1W8, Ireland
- 8Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Australia
The middle Miocene climate optimum (c. 14.2 to 13.8 Ma), a significant warm period, was followed by a series of step-wise global cooling and Antarctic ice-sheet expansion events visible in marine isotope records (e.g., Holbourn et al., 2013), the oldest of which is termed the mid-Miocene climate transition. Associated episodes of ice-sheet instability and iceberg calving are recorded by ice-rafted debris in mid- to high-latitude marine sediment, accessible via deep-sea sediment cores around the Antarctic margin. Paleo-ice sheet models indicate that step-wise ice-sheet growth in part reflects ice expansion across previously ice-free low-elevation regions (Gasson et al., 2016; Halberstadt et al., 2021). Such predictions are amenable to testing by detrital provenance analysis of ice-rafted debris. However, the small-volume and mineralogically impoverished samples which are typically recovered from distal marine sediment preclude use of conventional accessory heavy-mineral proxies: instead, use of a rock-forming mineral is necessitated.
Here, we present in-situ Rb-Sr, Ar-Ar, and Pb-isotope data from ice-rafted K-feldspar collected from mid-Miocene marine sediment in the Weddell Sea (Neofitu et al., 2024) and offshore Prydz Bay. Source regions for these depocenters respectively include the Recovery and Aurora sub-glacial basins, where ice-sheet embayment formation during warm periods is predicted. Our data suggest that the Wilkes and Aurora subglacial basins were free of marine-terminating ice during the middle Miocene climate optimum. During the transition, ice advanced to the coast across the Aurora sub-glacial basin, and both the Recovery and Aurora basins at least intermittently hosted marine-terminating ice during the subsequent cooling step.
Halberstadt et al., 2021, EPSL, 564, 116908, 10.1016/j.epsl.2021.116908;
Holbourn et al., 2013, Paleoceanography 28, 688–699, 10.1002/2013PA002538;
Gasson et al., 2016, PNAS 113, 3459–3464, 10.1073/pnas.1516130113;
Neofitu et al., 2024, EPSL, 641, 118824, 10.1016/j.epsl.2024.118824.
How to cite: Mark, C., Neofitu, R., Rösel, D., Zack, T., Barfod, D., Mark, D., Flowerdew, M., O'Connell, S., Kelley, S., Halpin, J., and Daly, J. S.: Where did the ice reach the sea? The utility of coupled K-feldspar Rb-Sr, Ar-Ar, and Pb-isotope analysis applied to mid-Miocene ice-rafted debris in Antarctic marine sediment , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12219, https://doi.org/10.5194/egusphere-egu25-12219, 2025.
