K. Perrot et al., SPATIAL AND TEMPORAL VARIATIONS OF SUBSIDENCE OF THE EAST PACIFIC RISE (0-23-DEGREES-S), Earth and planetary science letters, 160(3-4), 1998, pp. 593-607
The distributions of crustal depths as a function of age have been ana
lysed for the southeast Pacific region, along the East Pacific Rise, b
etween the Equator and the Easter microplate (23 degrees S), Using age
data and a new compilation of bathymetric data, subsidence rates (for
both eastern and western flanks), asymmetry of subsidence and zero-ag
e depths, are computed within flow-line corridors on the Nazca and Pac
ific plates. Variations of subsidence rates, axial depths and subsiden
ce asymmetry are examined both in space (within corridors) and time (w
ithin several age intervals). The variability in these parameters alon
g the strike of the East Pacific Rise is systematic and serves to defi
ne several orders of ridge segmentation. The largest variations of the
se parameters are correlated with the large-scale segmentation of the
ridge axis (i.e. transform faults and very large overlapping spreading
centres) and are interpreted as related to variations in mantle heter
ogeneities mainly dependent upon temperature. Smaller variations of su
bsidence parameters are correlated with second (and sometimes third-)
order segmentation of the ridge axis, which could be related to variat
ions in axial magmatic supply. Across-strike variations of subsidence
suggest the existence of small lateral temperature and density variati
ons in the mantle. When analysing the slope of the distribution of dep
th versus square root of age within corridors, we have observed the ex
istence of changes in the slope which occur at specific age limits. We
have estimated the subsidence over different age ranges in order to d
etermine the temporal evolution of subsidence parameters (rates and as
ymmetry). Such an analysis may inform on the past axial segmentation a
nd on the persistence of axial discontinuities in time. A Linear relat
ionship between subsidence rates and axial depths is determined for ea
ch age range and suggests that shallower segments subside faster than
deeper segments. Although a similar, statistically defined Linear rela
tionship exists for any mid-ocean spreading ridge (both for intermedia
te or fast-ultrafast spreading), the resultant slopes of this relation
ship vary from ocean to ocean and show that this relationship is not u
niversal over all oceans. (C) 1998 Elsevier Science B.V. All rights re
served.