Impact of India-Asia collision on SE Asia: the record in Borneo.

Impact of India-Asia collision on SE Asia: the record in Borneo. Borneo occupies a central position in the Sundaland promontory ofSE Asia. It has a complex Cenozoic geological history of sedimentationand deformation which began at about the same time that India iscommonly suggested to have started to collide with Asia. Some tectonicreconstructions of east and SE Asia interpret a large SE Asian blockwith Borneo at its center which has been rotated clockwise and displacedsouthwards along major strike-slip faults during the Cenozoic due to theindentation of Asia by India. However, the geological history of Borneois not consistent with the island simply forming part of a large blockextruded from Asia. The large clockwise rotations and displacementspredicted by the indentor model for Borneo are incompatible withpalaeomagnetic evidence and there is no evidence that the majorstrike--slip faults of the Asian mainland reach Borneo. Seismictomography shows there is a deep high velocity anomaly in the lowermantle beneath SE Asia interpreted as subducted lithosphere but it canbe explained just as well by alternative tectonic models as by theindentor model. Very great thicknesses of Cenozoic sediments are presentin Borneo and circum-Borneo basins, and large amounts of sediment weretransported to the Crocker turbidite fan of north Borneo from the Eoceneto the Early Miocene, but all evidence indicates that these sedimentswere derived from local sources and not from distant sources in Asiaelevated by India-Asia collision. The Cenozoic geological history ofBorneo records subduction of the proto-South China Sea and Miocenecollision after this ocean lithosphere was eliminated, and a variety ofeffects resulting from long-term subduction beneath SE Asia. There islittle to indicate that India-Asia collision has influenced the Cenozoicgeological record in Borneo. Tectonophysics, 451(1-4): 366-389.