--> --> ABSTRACT: Extrusion Tectonics in Southeast Asia: Constraints from South China Continental Margin, by Tung-Yi Lee, Ching-Hua Lo, Sun-Lin Chung, Ching-Ying Lan, Pei-Ling Wang, and Lawrence A. Lawver; #90913(2000).
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ABSTRACT: Extrusion Tectonics in Southeast Asia: Constraints from South China Continental Margin

Lee, Tung-Previous HitYiTop1, Ching-Hua Lo2, Sun-Lin Chung2, Ching-Ying Lan3, Pei-Ling Wang3, and Lawrence A. Lawver4
(1) National Taiwan Normal University, Taipei, Taiwan
(2) National Taiwan University, Taipei, Taiwan
(3) Academia Sinica, Taipei, Taiwan
(4) University of Texas at Austin, Austin, TX

Based on detailed plate reconstructions for the South China Sea region, it can be established that two continuous belts of structural highs extended from Taiwan to offshore southern Vietnam along the South China continental margin. The inner belt consists of Con Son swell, Dongsha massif, and the Central High in the Tainan Basin. The outer belt consisted of Natuna high, Paracel Islands, Macclesfield Bank, Reed Bank, the northern part of Palawan and Mindoro, and possibly the Tananao belt of Taiwan. The basement granites in these belts have similar chemical composition and comparable radiometric ages which indicate that they were generated in similar tectonic settings during Cretaceous time. Geochemical data from late Cretaceous to Paleogene basalts indicate that starting in the earliest Tertiary, the South China continental margin was highly attenuated. The two structural belts were located on the outermost part of the stretched South China continental margin and were under extension. At about 30 Ma, the first identifiable marine magnetic anomaly (A11) appeared between the eastern part of these two structural highs and seafloor spreading propagated to the southwest. However, extrusion of Indochina began around 27 Ma, and the continuing sea-floor spreading in the South China Sea was largely confined to the eastern part of the margin. Our model prefers that rifting and opening of the South China Sea took place prior to the extrusion of Indochina and in fact was necessary prior to extrusion.

AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia