Controlling processes of marginal ridge development

Transform faults, key elements of plate tectonics, play a crucial role in shaping transform
margins. Marginal ridges, which are elevated basement highs at margin borders, represent
one of the structural elements occurring at some transform margins.
This study examines marginal ridges and their failed candidates, which occur along the
Zenith-Wallaby-Perth transform fault zone in West Australia, using seismic and gravity data,
and plate reconstructions to investigate their development histories.
Existing models of marginal ridge development often include processes such as thermal
expansion-related uplift, flexural uplift and flower structure development. However, data
from the study area suggest a more complex mechanism, which is related to the formation
of strike-slip faults and pull-apart basins inside the transform fault zone.
This study proposes a model of the marginal ridge formation characterized by the evolving
faulting during continental and continental-oceanic stages of the transform development.
The nucleation and linkage of strike-slip faults along the future transform fault zone lead to
the formation of pull-apart basins, characterized by a complex fault system. In the same
time, (1) initially broad zone of deformation undergoes progressive focusing and (2) fault
activity decays along the transform strike towards the ocean. Depending on the duration of
fault activity, some parts of the initial strike-slip fault zones and pull-aparts develop further,
while others are abandoned. In regions where faults remain active for extended periods
during the continental-oceanic stage of the transform development, marginal ridges may
develop, and even occasionaly evolve into micro-continents separated from the continent.
Further complexity in their development is the effect of the pre-existing anisotropy in
regions of their development.