Publication Date:
2016-11-10
Description:
We use recently published, high-resolution reconstructions of the Southwest Indian Ridge to test whether a previously described systematic difference between Global Positioning System (GPS) and 3.16-Myr-average estimates of seafloor spreading rates between Antarctica and Africa is evidence for a recent slowdown in Southwest Indian Ridge seafloor spreading rates. Along the Nubia-Antarctic segment of the ridge, seafloor opening rates that are estimated with the new, high-resolution reconstructions and corrected for outward displacement agree well with geodetic rate estimates and reduce previously reported, highly significant non-closure of the Nubia-Antarctic-Sur plate circuit. The observations are inconsistent with a slowdown in spreading rates and instead indicate that Nubia-Antarctic plate motion has been steady since at least 5.2 Ma. Lwandle-Antarctic seafloor spreading rates that are estimated from the new high-resolution reconstructions differ insignificantly from a GPS estimate, thereby implying steady Lwandle-Antarctic plate motion since 5.2 Ma. Between the Somalia and Antarctic plates, the new Southwest Indian Ridge reconstructions eliminate roughly half of the systematic difference between the GPS and MORVEL spreading rate estimates.We interpret the available observations as evidence that Somalia-Antarctic spreading rates have been steady since at least 5.2 Ma and postulate that the remaining difference is attributable to random and/or systematic errors in the plate kinematic estimates and the combined effects of insufficient geodetic sampling of undeforming areas of the Somalia plate, glacial isostatic adjustment in Antarctica and transient deformation triggered by the 1998 M w = 8.2 Antarctic earthquake, the 2004 M w = 9.3 Sumatra earthquake, or possibly other large historic earthquakes.
Keywords:
Geodynamics and Tectonics
Print ISSN:
0956-540X
Electronic ISSN:
1365-246X
Topics:
Geosciences
Published by
Oxford University Press
on behalf of
The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
