HR: 0800h
AN: T41A-0387    [Abstracts]
TI: Rifted Structure of the Vietnam Continental Margin Near the South China Sea Spreading Center
AU: * Reid, I D
EM: idr@geol.ku.dk
AF: Department of Geography and Geology, University of Copenhagen, Ø ster Voldgade 10, Copenhagen, DK-1350, Denmark
AU: Fyhn, M B
AF: Department of Geography and Geology, University of Copenhagen, Ø ster Voldgade 10, Copenhagen, DK-1350, Denmark
AU: Boldreel, L O
AF: Department of Geography and Geology, University of Copenhagen, Ø ster Voldgade 10, Copenhagen, DK-1350, Denmark
AU: Nielsen, L H
AF: Geological Survey of Denmark and Greenland, Ø ster Voldade 10, Copenhagen, DK-1350, Denmark
AU: Duc, N A
AF: Vietnam Petroleum Institute, Yen Hoa, Cau Giay, Hanoi, Viet Nam
AU: Huyen, N T
AF: Vietnam Petroleum Institute, Yen Hoa, Cau Giay, Hanoi, Viet Nam
AU: Thang, L D
AF: Vietnam Petroleum Institute, Yen Hoa, Cau Giay, Hanoi, Viet Nam
AB: The extinct spreading center of the South China Sea intersects the continental margin off Vietnam, providing an excellent opportunity to study the interaction of these two features. As part of a collaborative project between the Geological Survey of Denmark and Greenland, the University of Copenhagen and the Vietnam Petroleum Institute, the crustal structure of this area has been investigated by the use of seismic reflection profiles, to provide control on the sedimentary and basement structure, combined with modelling of gravity data from global satellite altimetry, to constrain the crustal thickness. A complex pattern of rifting is seen, which may be ascribed to the complex stress fields of the propagating rift axis, together with an apparent progression in structure. In the more oceanic area, the rifting is relatively sharp, with fairly rapid crustal thnning of about 10 km. Towards the continent, in the region of the tip of the rift axis, the crustal thinning is less, around 5-7 km, and takes place over a greater distance. In the absence of data on the deep crustal structure it is not possible to determine the absolute crustal thickness with certainty, but the gravity modelling suggests that the pre-existing crust was no more than 20 km thick, having been thinned in earlier stages of formation of the South China Sea. A preliminary analysis of the isostatic balance along the various transects was inconclusive but suggests that the sedimentary sequences are largely isostatically compensated, rather than being supported by lithospheric rigidity. Detailed modelling of the rifting and subsidence may provide further insight into the processes that occur when an oceanic spreading center intersects and propagates into a continental margin.
DE: 8105 Continental margins: divergent (1212, 8124)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting