Borneo Sediment Yields
Borneo is the third largest island in the world after Greenland and New Guinea. Although it is not unusually high, it is surrounded by important sedimentary basins, largely filled in the past 25 Ma, which are unusually deep. The volume of sediment deposited in the basins around Borneo indicates that at least 6 km of crust has been removed by erosion during the Neogene.
The amount of tectonic uplift implied by this is not reflected in a large area of high mountains on the island, which has an average elevation much lower than that of the Alps or Himalayas. High weathering and erosion rates in the tropical climate of SE Asia are likely to have been an important factor governing the formation of relief in Borneo and consequently controlled the structural development of the orogenic belt.
Very rapid removal of material by erosion prevented tectonic denudation by faulting: around Borneo there was no lithospheric flexure due to thrust loading and no true foreland basins were developed. The sediment was deposited adjacent to the orogenic belt in older, deep oceanic basins. In terms of sediment yield, the Borneo mountains are comparable in importance to mountain ranges such as the Alps or Himalayas. However, the differences in elevation and structural style suggest that mountain belts formed in regions of high erosion rates may be different from those formed in other settings and the effects of climate need to be considered to understand orogenic evolution. Work is continuing to try to determine what has driven the uplift required to produce the sediments.
Hall, R. & Nichols, G. J. 2002. Cenozoic sedimentation and tectonics in Borneo: climatic influences on orogenesis. In: Jones, S. J. & Frostick, L. (Eds.) Sediment Flux to Basins: Causes, Controls and Consequences. Geological Society of London Special Publication, 191, 5–22. [pdf]