f Rotation of Borneo Revisited – New Inferences from Gravity Data and Plate Reconstructions

Borneo has commonly been considered to have undergone two stages of major anti-clockwise rigid-block plate rotation - 50° between 80 and 30 Ma and 40° between 30 and 10 Ma (e.g. Fuller et al., (1999) and Hall (2002), based on interpretations of palaeomagnetic data from Kalimantan and Sarawak). These interpretations have recently been challenged (Cullen, 2010). Considerations based on gravity data and plate modelling add further concerns. Cullen (2010) pointed out that the earlier authors had rejected those palaeomagnetic data that did not match their model, using the argument of young re-magnetisation. If those data are taken into account, the 30-10 Ma anti-clockwise rotation must have been restricted to smaller tectonic blocks, with no rigid-plate rotation of Borneo as a whole. It should also be noted that the palaeomagnetic data from Borneo provide similar results to those for the Malay Peninsula, Sulawesi, the Celebes Sea and parts of the Philippines; this suggests that any rotation should be applied to a block much larger in extent than just Borneo (Fuller et al., 1999).