Denudation history of onshore central Vietnam: constraints on the Cenozoic evolution of the western margin of the South China Sea

Apatite fission track analysis is used to monitor the timing and rate of upper crustal cooling and denudation across central Vietnam in response to rifting of the South China Sea. Results show regional denudation in the syn- and post-rift phases of the South China Sea occurred at a similar rate (similar to 40 +/- 10 m/Myr), consistent with the sedimentation record in adjacent offshore basins. This suggests that extension was not the dominant factor controlling Cenozoic denudation, probably because the study area was sufficiently distant from the actively rifted continental margin. A significant change in regional cooling rate during the Upper Miocene (inferred denudation rates also shift from similar to 34 m/Myr to 390-500 m/Myr) is linked to enhanced erosion and deposition of prograding sediments in adjacent offshore basins. This shift in denudation is associated, and contemporaneous, with initiation of regional basaltic magmatism and development of topography. (C) 2000 Elsevier Science B.V. All rights reserved.