Christopher C. Olson1,
Steven L. Dorobek2
(1) Texas A&M University, College Station, TX
(2) Texas A&M University
Abstract: Comparison of structural styles, regional subsidence patterns, and depositional patterns across the Nam Con Son and Cuu Long Basins, offshore southeast Vietnam
The Cuu Long and Nam Con Son (NCSB) basins are Tertiary rift basins located offshore southeast Vietnam. Observations from regional 2D seismic data indicate both basins consist of smaller sub-basins with similar E-W to ENE-WSW basin axes and rift onset histories (late Eocene(?)-Oligocene time). However, structural styles, subsidence histories, basin fills, and timing of tectonic quiescence are markedly different for each basin. The Cuu Long Basin is characterized by smaller, shallower (involving only the upper crust), and more closely spaced extensional structures than in the NCSB. Additionally, almost no deformation affected the Cuu Long Basin once extension ceased in Oligocene time. Post-rift stratigraphic patterns in the Cuu Long Basin also show little variation in thickness across the basin, suggesting that extension did not generate a significant post-rift thermal anomaly in the lithosphere beneath the basin.
Farther to the South, the NCSB underwent pulsed regional subsidence related to three phases of rifting from late Eocene (?) to Miocene time. Unlike the Cuu Long Basin, the NCSB is characterized by more prevalent major extensional faults, and was subjected to varying magnitudes of structural inversion during middle Miocene time. Stratigraphic thickness patterns within the NCSB indicate that tectonic subsidence has continued through the Pleistocene at varying rates across the basin, although there is an increase in post-rift subsidence toward the southeast. As the NCSB subsided during post-rift phases, sediment bypassed the Con Son High to the north and formed massive Miocene-Pliocene deltaic complexes that prograded toward the central and southern regions of the basin.
AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana