Influence of inherited basement structures on the active Sumatran Fault
and Volcanic Arc, Indonesia
Abstract
We present a novel tectonic and structural framework for the Sumatran
Volcanic Arc and Sumatran Fault System (SFS), based on a comprehensive
compilation of the controls of heterogeneities in both subducting and
overriding plate on the local to lithospheric-scale geology. A new
conceptual model is proposed to explain the interaction between
pre-existing inherited basement structures, which are well exposed along
the arc, with the much younger SFS. The model also illustrates the
relationship between brittle deformation and nearby magmatism-volcanism.
We present a novel structural restoration of the island prior to the SFS
strike-slip faulting contributing to in-depth understanding of the
initial condition of the island, especially in view of the basement
structures underlying the volcanic arc and the inherited basement
structures. More detailed structural analysis along the SFS showcases
different interaction styles between SFS and the basement structures.
Different intersection angles between those two structural features
create different deformation styles along the arc. An elongated
rhomboidal pull-apart basin is expected where the segments of SFS are
parallel or sub-parallel to the basement structures, while a more
complex and irregular pull-apart basin is developed where the
intersection angle is larger. The structural controls on volcanism along
the arc are located along the basement structures, and demonstrate that
they are only partially in tune with the SFS fault structures.
Furthermore, the different deformation styles and interaction between
volcanism-tectonism along the arc have been grouped into two different
main tectono-volcanic domains, with distinctive transitional area around
the Toba Caldera Complex.