New Insight on the Rotation and Deep Crustal Structure of Java and the Lesser Sunda Islands Based on Arc Volcano Distribution
Abstract
We employ the distribution of arc volcanoes in the Java and Lesser Sunda Islands (Java LS) as a proxy for the stress regime of the upper plate. Three great circle segments in the Java LS form an en-echelonpattern suggesting an oblique subduction system, in contrast to the common view that this is an orthogonal subduction system in Java. We hypothesise that the lineaments represent the strike-slip stepover structures in the deep crust and that their overlaps, in West and East Java, are pull-apart structures. Surface structures, mostly folds and formation boundaries, also show trench-parallel strain manifest as the 'S'-shape deformation patterns observed along the islands from lineament mapping. Trench geometry, great circle volcano segments, and subduction directions are compared to constrain obliquity variations along Java LS. Most of the Java LS southern block, bounded by the trench in the south and the volcanoes to the north, experienced eastern lateral movement with a low trench-parallel component (<0.45 ratio over the trench-normal component). This is in contrast to strongly trench-parallel movement (0.8 to 1.5 average ratio) of Sumatra's southern block movement towards the west, most conspicuously shown by the dextral strike-slip Great Sumatra Fault. Lateral movements of the Java LS and Sumatra blocks areinfluenced by trench geometry which has been modified at each end of the arc due to the subduction of Australia and India. The northward deflection of the arc by Australian plate caused a rotation of Java LS about a pole of rotation, about which the lateral movement changes from eastern directed to western directed, located at about 108oE which coincides with the great circle lineament overlap in West Java. Sinistral strike-slip deep crustal movement occurs to the east of the pole while dextralmovement occurs to the west of the pole and continues to Sumatra and propagates to the surface as the trench-parallel component gets significantly higher. Therefore, we suggest the rotation of Java LS developed block's lateral movement and generated strike-slip stepover structures in the deep crust.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.T21G0313A
- Keywords:
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- 8104 Continental margins: convergent;
- TECTONOPHYSICSDE: 8170 Subduction zone processes;
- TECTONOPHYSICS