S. Dominguez et al., Deformation of accretionary wedges in response to seamount subduction: Insights from sandbox experiments, TECTONICS, 19(1), 2000, pp. 182-196
Sandbox experiments, using a two-dimensional and a three-dimensional approa
ch, are used to study the deformation of margins in response to seamount su
bduction. Successive mechanisms of deformation are activated during the sub
duction of conical seamounts. First, reactivation of the frontal thrusts an
d compaction of the accretionary wedge is observed. Then, back thrusting an
d, conjugate strike-slip faulting develops above the leading slope of the s
ubducted seamount. The basal decollement is deflected upward in the wake of
the subducting high, and a large shadow zone develops behind the seamount
trailing slope. Consequently, frontal accretion is inhibited and part of th
e frontal margin is dragged into the subduction zone. When the main decolle
ment returns to its basal level in the wake of the seamount, the margin rec
ords a rapid subsidence and a new accretionary wedge develops, closing the
margin reentrant. The sediments underthrusted in the wake of the seamount i
nto the shadow zone, are underplated beneath the rear part of the accretion
ary wedge. Substantial shortening and thickening of the deformable seaward
termination of the upper plate basement, associated with basal erosion is o
bserved. Seamount subduction induces significant material transfer within t
he accretionary wedge, favors large tectonic erosion of the frontal margin
and thickening of the rear part of the margin. The subduction and underplat
ing of relatively undeformed, water-ladden sediments, associated with fluid
expulsion along the fractures affecting the margin could modify the fluid
pressure along the basal decollement. Consequently, significant variations
of the effective basal friction and local mechanical coupling between the t
wo plates could be expected around the subducting seamount.