Crustal Structure and Plate Reconstruction of the South China Sea and its Bearing on Petroleum Systems
Reemst, Paul¹; Kusznir, Nick²; Gozzard, Simon²; Franke, Dieter³; Teasdale, Jonathan¹; Henstra, Gijs¹; Frankowicz, Edyta¹
¹Exploration New Ventures, Shell International, the Hague, Netherlands.
²Department of Earth and Ocean Sciences, University of Liverpool, Liverpool, United Kingdom.
³BGR Federal Institute for Geosciences and Natural Resources, Hannover, Germany.
The Cenozoic history of the South China Sea is characterized by a complex interplay of different types of lithospheric deformation. These include large scale lateral movement, lithospheric rifting, sea-floor spreading and intra-plate thrusting and/or subduction.
In the western part of the South China Sea and onshore Indochina rotation of the Indochina block causes a lateral displacement of several hundreds of kilometers along major shear zones. This deformation is partly contemporaneous with lithospheric rifting during the Paleogene leading to oceanic seafloor spreading between ~35 and 20.5-16 Ma. On the southern margin of the South China Sea, contractional deformation occurs as exemplified by the Sarawak orogeny onshore NW Borneo.
We quantify and map the amount of crustal thinning by means of an oceanic age-dependent gravity inversion and a series of lithospheric scale forward modeling techniques. The crustal thinning and lateral displacement that occur as a result of rifting as well as the large scale lateral movements and rotation are incorporated into a plate tectonic reconstruction of the region. This unique combination allows us to test different hypothesis on the paleogeography of the South China Sea, for instance during the time of deposition of potential source rock intervals. The results of the gravity inversion are also compared with recently acquired seismic data offshore Vietnam and China. These data show an excellent agreement between the modeled and seismically interpreted base of the crust. As suggested by the results from the gravity modeling, it appears that some areas such as the Phu Khanh margin (offshore western Vietnam) have undergone an extreme amount of extension, similar to models of so called hyperextended continental margins. The presence of hyperextended continental crust has particular relevance to the presence of potential petroleum systems in the overlying basins as can be demonstrated by the charge history, reservoir type and trapping styles of these basins.
AAPG Search and Discovery Article #90155©2012 AAPG International Conference & Exhibition, Singapore, 16-19 September 2012