Subduction polarity reversal (SPR) is a key subduction initiation mechanism often associated with arc-continent collision zones. Northern Borneo has long been recognized as a location where sequential but opposing subduction zones were present in the Miocene, but has not been examined in the context of SPR. Here, we exploit teleseismic data from northern Borneo to investigate crustal thickness variations using Virtual Deep Seismic Sounding (VDSS). Our results reveal a thick crustal root beneath the Crocker Range and an area of relatively thin crust in the southeast, which appears to extend northeast into the Sulu Sea, where back-arc rifting behind the younger subduction zone developed. Overall, our findings are consistent with predictions from numerical models of SPR involving arc-continent collision, but with several important differences?including a substantial mountain range and more limited back-arc rifting that can be attributed to northern Borneo being an example of SPR involving continent-continent collision.
We thank MetMalaysia for allowing access to their restricted data. H.T.L. acknowledges the fieldwork grant awarded by the University of Cambridge's LWA Research Fund and St Edmunds' Cherry Hume Prize. S.P. acknowledges support from the Natural Environmental Research Council (NERC) Grant NE/R013500/1 and the European Union's Horizon 2020 program under Marie Sklodowska-Curie Grant Agreement 790203. We thank NERC's Geophysical Equipment Facility for loan 1038. Seismic data from the nBOSS network will be accessible through the IRIS Data Management Center (http://www.iris.edu/mda) from February 2023 (see https://doi.org/10.7914/SN/YC_2018). Waveform data recorded by the nBOSS network were processed and archived by C. A. Bacon. Details on the status of this database may be obtained from N.R.
- northern Borneo
- crustal thickness
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David Graham Cornwell (Manager)Geology and Geophysics
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