HR: 11:35h
AN: T22C-06    [Abstracts]
TI: Timing, Structural Styles, and Tectonic Significance of Neogene Basin Inversion Across the South China Sea and Indonesian Back-Arc Region
AU: * Dorobek, S L
EM: dorobek@geo.tamu.edu
AF: Texas A&M University, 3115 TAMU, Dept of Geology & Geophysics, College Station, TX 77843-3115 United States
AU: Olson, C C
EM: Chris_Olson@anadarko.com
AF: Anadarko Petroleum Corp., 1201 Lake Robbins Drive, The Woodlands, TX 77380 United States
AB: Basin inversion is a common phenomenon in many intracontinental extensional or transtensional settings that are subjected to later contractional deformation. Numerous examples of inverted Paleogene rift basins are found in the Indonesian back-arc region and southern and western parts of the South China Sea. Inversion was widespread across the broad region, mainly began in latest Oligocene-early Miocene time, and locally continues to the present day. Most basins were fully inverted in less than 15 Myr and inversion typically involved reactivation of preexisting extensional fault systems that formed during Paleogene rifting. We examined the tectonic styles and regional timing of basin inversion across this region in order to understand the tectonic and geodynamic reasons for the inversion. The timing of regional inversion and structural styles associated with inversion reflect roughly N-S to NNW-SSE oriented intraplate compressive stress, which suggests that incipient collision of Australian continental crust along the eastern Indonesian archipelago and `South Chinese/Vietnamese' crust along the Borneo/South Palawan margin were responsible for the widespread inversion. A fundamental change from uncoupled to coupled subduction along the Indonesian trench and Borneo/South Palawan margin, coincident with the incipient subduction of continental crust along these convergent margins during latest Oligocene-early Miocene time, may explain why intraplate compressive stress was transmitted across the Indonesian back-arc and southern South China Sea (Sunda Shelf) region. Prior to late Oligocene time, subduction was essentially uncoupled and Paleogene rift basins across the Indonesian backarc and Sunda Shelf region were thermally subsiding. The rheology of Sundaland and offshore Southeast Asian continental lithosphere also was especially conducive to widespread, nearly synchronous basin inversion during Neogene time, which likely reflects the low viscosity nature of the mantle lithosphere across the region during the early post-rift history of these basins.
DE: 8103 Continental cratons
DE: 8110 Continental tectonics: general (0905)
DE: 8169 Sedimentary basin processes
SC: Tectonophysics [T]
MN: Fall Meeting 2005