Mass accumulation rates in Asia during the Cenozoic

This work establishes estimates of mass accumulation rates in 18 mostly offshore sedimentary basins in Asia since the beginning of the Cenozoic, ≈ 66 Ma. The estimates were derived from isopach maps, cross-sections and drill holes or stratigraphic columns assuming regional similarity of the strata. Average solid phase volumes and accumulation rates were calculated for nine epochs approximately corresponding to geological periods: Palaeocene (≈ 66–58 Ma), Eocene (≈ 58–37 Ma), Oligocene(≈ 37–30 and 30–24 Ma), Miocene (≈ 24–17, 17–11 and 11–5 Ma), Pliocene (≈ 5–2 Ma) and Quaternary (≈ 2–0 Ma). These rates shed new light on the geological history of Asia since the onset of the collision of India with Asia (≈ 50 Ma). The overall average accumulation rates curve for Asian sedimentary basins since the beginning of the Tertiary shows an exponential form with slow accumulation rates (less than 0.5 × 106km3Myr− 1) until the beginning of the Oligocene, more than 15 Myr after the onset of the collision. From the Oligocene onwards rates increase quickly in an exponential manner, reaching their maximum values in the Quaternary (more than 1.5 × 106km3Myr− 1). From these observations we suggest that extrusion and crustal shortening are complementary processes that have been successively dominant throughout the India–Eurasia collision history. At smaller scales one may distinguish between independent histories at the subcontinental and basin scales. This permits a comparison of the relative importance of tectonic and climatic erosion processes affecting the different mountain belts of Asia during the Cenozoic.