Disentangling intergalcial sea level and global dynamic topography: analysis of Madagascar

Stephenson, Simon N. and White, N. J. and Li, T. and Robinson, L. F. (2019) Disentangling intergalcial sea level and global dynamic topography: analysis of Madagascar. Earth and Planetary Science Letters. ISSN 0012-821X DOI https://doi.org/10.1016/j.epsl.2019.04.029 (In Press)

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Abstract

Global inventories of stable sea-level markers for the peak of the last interglacial period, Marine Isotopic Stage (MIS) 5e, play a pivotal role in determining sea-level changes and in testing models of glacial isostatic adjustment. Here, we present surveying and radiometric dating results for emergent terraces from northern Madagascar, which is generally regarded as a stable equatorial site. Fossil coral specimens were dated using conventional and open-system corrected uranium series methods. Elevation of the upper (undated) terrace decreases from 33.8 m to 29.5 m over a distance of 35 km. An intermediate terrace has an average radiometric age of ka (i.e. MIS 5e). Its elevation decreases from 9.3 m to 2.8 m over a distance of 80 km. The record of the lowest terrace is fragmentary and consists of beach rock containing rare corals with ages of 1.6–3.8 ka. The spatial gradient of the MIS 5e marker is inconsistent with glacio-isostatic adjustment calculations. Instead, we propose that variable elevations of this marker around Madagascar, and possibly throughout the Indian Ocean, at least partly reflect spatial patterns of dynamic topography generated by sub-plate mantle convection.

Item Type: Article
Uncontrolled Keywords: 2019AREP; IA75
Subjects: 02 - Geodynamics, Geophysics and Tectonics
Divisions: 02 - Geodynamics, Geophysics and Tectonics
08 - Green Open Access
Journal or Publication Title: Earth and Planetary Science Letters
Identification Number: https://doi.org/10.1016/j.epsl.2019.04.029
Depositing User: Sarah Humbert
Date Deposited: 08 May 2019 15:37
Last Modified: 20 May 2020 00:02
URI: http://eprints.esc.cam.ac.uk/id/eprint/4480

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