| Ocean: | Pacific |
| Spreading center type: | Microplate spreading ridge |
| Time of cessation: | 2 Ma, C2n (Klein et al., 2005) |
| Subsequent active spreading center: | The Cocos-Nazca spreading center was active simultaneous to the failed propagtor and remains the active spreading centre in the region |
A short, 100 km long free-air gravity low trending NW-SE, oblique to identified magnetic isochron of the Cocos-Nazca plate boundary, is referred to as the Nazca Ridge failed propagator. This structure was identified by Klein et al. (2005) and is discussed in a number of subsequent, related studies of the region (Smith et al., 2011; Schouten et al., 2008; Mitchell et al., 2011).
Several geodynamic explanations have been presented to explain the formation and cessation of the failed spreading segment. Klein et al. (2005) argue that the trough represents a failed propagator, that they suggest formed the northern boundary of a rotating microplate that was one of a pair of rotating microplates linking the East Pacific Rise with the Cocos-Nazca spreading centre. Schouten by al. (2008) later suggested that gap between the two major spreading centres in the eastern Pacific (the East Pacific Rise and the Cocos-Nazca spreading centre) led to development of extensional stresses that caused a 'crack' in the crust and the development of this failed propagator.
This ridge was not included in our statistical analyses because it did not meet our inclusion criteria as a large-scale extinct ridge, however the morphology of the structure and available evidence supports its origin as an extinct spreading center (Klein et al., 2005; Smith et al., 2011; Schouten et al., 2008; Mitchell et al., 2011).
Klein, E. M., Smith, D. K., Williams, C. M. and Schouten, H., 2005, Counter-rotating microplates at the Galapagos triple junction, Nature, v. 433, p. 855-858.
Mitchell, G. A., Montesi, L. G. J., Zhu, Wenlu, Smith, D.K., and Schouten, H., 2011, Transient rifting north of the Galapagos triple junction, Earth and Planetary Science Letters, v. 307, p. 461-469.
Schouten, H., Smith, D. K., Montesi, L. G. J., Zhu, W., and Klein, E. M., 2008, Cracking of the lithosphere north of the Galapagos triple junction, Geology, v. 36, no. 5, p. 339-342.
Smith, D., Schouten, H., Zhu, When-lu, Montesi, L.G.J., Cann, J. R., 2011, Distributed deformation ahead of the Cocos-Nazca rift at the Galapagos triple junction, Geochemistry, Geophysics, Geosystems, v. 12, no. 11, doi:10.1029/2011GC003689.
