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Evolution of Arc-Continent Collision Controlled by Inherited Lithospheric Scale Structures

From west to east along the Sunda-Banda arc in SE Asia, convergence of the Indo-Australian plate transitions from subduction of oceanic lithosphere to arc-continent collision. This region of eastern Indonesia and Timor-Leste provides an opportunity for unraveling the processes that occur during collision between a continent and a volcanic arc, and can be viewed as the temporal transition of this process along strike. We have collected a range of geological and geophysical data to place constraints on the geometry and history of arc-continent collision. Utilizing ~4 years of new broadband seismic data we image the structure of the crust through to the uppermost mantle. Ambient noise tomography of the lithosphere shows velocity anomalies along strike and across the arc, that are attributed to the structure of the incoming and colliding Australian plate. At upper mantle depths, the boundary between oceanic subduction to continental collision appears reflected in new teleseismic based images, coinciding with previously identified changes in the geochemistry of back-arc volcanics. Reconstruction of uplift from river profiles hints at dynamic uplift at the far ends of Timor and western Sumba, inferred to be associated with the incoming and collided plate structure. Altogether, we suggest that the tectonic evolution of this region is defined by inherited structure of the Gondwana rifted continental margin.

Presenting Author: Meghan S. Miller

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