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Accurate measurements of residual topography from the oceanic realm
Author(s) -
Winterbourne Jeffrey,
White Nicky,
Crosby Alistair
Publication year - 2014
Publication title -
tectonics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.465
H-Index - 134
eISSN - 1944-9194
pISSN - 0278-7407
DOI - 10.1002/2013tc003372
Subject(s) - geology , residual , lithosphere , gravity anomaly , ocean surface topography , crust , geophysics , oceanic crust , bathymetry , mantle (geology) , seismology , wavelength , density contrast , low velocity zone , geodesy , subsidence , tectonics , subduction , geomorphology , paleontology , algorithm , computer science , oceanography , physics , optoelectronics , structural basin , astronomy , oil field
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 10 3 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 (∼10 2 km) low‐viscosity layer beneath the lithosphere. Our global compilation should play a significant role in helping to refine predictive geodynamical models.