Accurate measurements of residual topography from the oceanic realm

Winterbourne, J. and White, N. J. and Crosby, A. G. (2014) Accurate measurements of residual topography from the oceanic realm. Tectonics, 33 (6). pp. 982-1015. ISSN 0278-7407, ESSN: 1944-9194 DOI 10.1002/2013TC003372

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Official URL: http://onlinelibrary.wiley.com/doi/10.1002/2013TC0...

Abstract

In the oceans, our understanding of plate subsidence as a function of age permits residual depth anomalies to be identified and mapped. These anomalies may reflect dynamic topography and could be an important means for constraining convective circulation of the sublithospheric mantle. Here we analyze a global database of seismic reflection and wide-angle profiles from heavily sedimented oceanic crust, which abuts continental lithosphere. At 449 locations, we calculated water-loaded subsidence, compared it with a reference age-depth relationship, and determined residual depth. We then combined these spot measurements of residual depth with observations from mid-oceanic ridges and from selected ship track bathymetry to construct a global map of residual depth. Our results suggest that the amplitude of residual depth varies by up to ±1 km with wavelengths of order 103 km. We compare our residual depths with free-air gravity and seismic tomographic anomalies. Our results show that residual depths correlate with long-wavelength gravity anomalies. In contrast, correlations between residual depths and vertically averaged shear velocity anomalies within the upper and/or the lower mantle are weaker. The largest discrepancies occur at short (∼1000 km) wavelengths. These combined observations suggest that residual depth anomalies could be generate by density variations within a thin (∼102 km) low-viscosity layer beneath the lithosphere. Our global compilation should play a significant role in helping to refine predictive geodynamical models.

Item Type: Article
Uncontrolled Keywords: 2014AREP; IA67;
Subjects: 02 - Geodynamics, Geophysics and Tectonics
Divisions: 02 - Geodynamics, Geophysics and Tectonics
08 - Green Open Access
Journal or Publication Title: Tectonics
Volume: 33
Page Range: pp. 982-1015
Identification Number: 10.1002/2013TC003372
Depositing User: Sarah Humbert
Date Deposited: 11 Apr 2014 14:08
Last Modified: 10 Jan 2015 01:00
URI: http://eprints.esc.cam.ac.uk/id/eprint/3026

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