| Age, spreading rates, and spreading asymmetry of the world's ocean crust |
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The authors present four companion digital models of the age, age uncertainty, spreading
rates and spreading asymmetries of the world's ocean basins as geographic and Mercator
grids with 2 minute resolution. The grids include data from all the major ocean basins
as well as detailed reconstructions of back-arc basins. The age, spreading rate and
asymmetry at each grid node is determined by linear interpolation between adjacent
seafloor isochrons in the direction of spreading. Ages for ocean floor between the
oldest identified magnetic anomalies and continental crust are interpolated by geological
estimates of the ages of passive continental margin segments. The age uncertainties
for grid cells coinciding with marine magnetic anomaly identifications, observed or
rotated to their conjugate ridge flanks, are based on the difference between gridded
age and observed age. The uncertainties are also a function of the distance of a given
grid cell to the nearest age observation, and the proximity to fracture zones or other
age discontinuities. Asymmetries in crustal accretion appear to be frequently related
to asthenospheric flow from mantle plumes to spreading ridges, resulting in ridge
jumps towards hotspots. The authors also use the new age grid to compute global residual
basement depth grids from the difference between observed oceanic basement depth and
predicted depth using two alternative age-depth relationships. The new set of grids
helps to investigate prominent negative depth anomalies, which may be alternatively
related to subducted slab material descending in the mantle or to asthenospheric flow.
A combination of these digital grids and the associated relative and absolute plate
motion model with seismic tomography and mantle convection model outputs represent
a valuable set of tools to investigate geodynamic problems. |
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