Geophysics Appearance of The South China Sea

Eddy Mirnanda


South China Sea (SCS) is underlain by sediments of an average density 2.10 g/cm3 of 2 km thickness at its central part up to 10 km in the margins. The basement rock is the upper and lower crust of densities 2.67 and 2.85 g/cm3 respectively of varying thicknesses. The thinnest crustal rock is at the centre of SCS that is called the South China Sea Basin (SCSB). The Mohorovicic discontinuity is about 15 km depth below the SCSB. Heatflow values in this basin vary from 2 to 3.5 HFU.

Lineations of total magnetic anomaly are generally in a west-east direction covering the whole study area. However, an elongated northeast-southwest lineation of dipole anomaly separates the west-east anomaly patterns in the north from those in the south. This feature is also observed in the gravity map. These elongated patterns of the total magnetic features are in coincident with the occurrences of seamounts inferred being remnant of extinct seafloor spreading. Because of this spreading a crustal extension had taken place that separated Kalimantan from the mainland of China to restore its present position. A paleomagnetic study result confirms this hypothesis.

The Palawan trench is marked by north-east trending magnetic and gravity anomaly that is inferred being traces of a remnant subduction zone. This anomaly forms a boundary between the Zengmu also called the Sarawak basin and the SCSB. Here, heat flow value is 1 to 2 HFU. This value in coincident with gravity gradient of 2.5 mGal/km also represents an active subduction of the Manila trench north of the Palawan Island. The Manila trench is supposed to be the energizing source of volcanism and earthquake in the Phillippines. Free-air and Bouguer anomaly of the order of 50 to 60 mGal and magnetic of about 100 nT represent the Zengmu basin in the Sunda Shelf. This basin is underlain by sediments of 2.10 g/cm3 of 8 km thickness and also crustal rock which is much thicker than the one underneath the SCSB. Strong topographic relief at the surfaces of sedimentary layer and the crustal rock is very my much associated with normal faulting that may cause fluctuation of the free-air values.

The continental margins of Sarawak and the Sunda Shelf are areas of hydrocarbon deposits now still in production, whereas the offshores Vietnam and Hainan are promising target for hydrocarbon exploration.


South China Sea (SCS); geophysics appearance; South China Sea Basin (SCSB); Serawak Basin; Zengmu Basin; magnetic and gravity anomaly; Heatflow

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Karig, D.E. 1971. Origin and Developmen of Marginal Basins in the Western Pacific. Journal of Geophysical Research, 76, 2543-2561.

2 --------------. 1973. Plate Convergenc between the Philippines and the Ryuky Islands. Marine Geology, 14, 53-168.

3 Qin Xu-wen, Zhao Bin, Li Fu-yuan, Zhang Bao-jin, Wang Hou-jin, Zhang Ru-we, Hec Jia-xio and Chen Xi. 2019. Deep Structural Research of The South China Sea: Progresses and Direction, China Geologi Journal, China Geolgical Survey, 2 (4), 530-540,

4 Taylor, B. and Hayes, D.E. 1980. The Tectonic Evolution of the South Cina Sea Basin, The Tectonic and Geologic Evolution of Southeast Asian Seas amd islands. Geophys. Monograph, American Geophysical Union, 23, 89-104.

5 Hall Robert and Breitfeld H. Tim. 2017. Nature and Demise of the Proto-South China Sea. Bulletin of the Geological Society of Malaysia, 63, 61-76.

6 Xia Kan-Yuan and Zhou Di. 1995. The Geophysical Characteristics and Evolution of Northern and Southern margins of the South China Sea. Geol. Soc. Malaysia, Bull., 33, 225-240.

7 Studies in East Asian Tectonics and Resources (SEATAR). 1980. Banda Sea, CCOP Project Office.

8 GETECH (Geopphysical ExplorationTechnology) and IGC (Indonesian Gravity Commission). 1995. South-East Asia Gravity Project, GETECH Technical Report.

9 Bowin, C., Warsi Waris and Milligan, J. 1982. Free-Air Gravity Anomaly Atlas of the World. Geological Society of America Map and Chart Series, No. Mc-46.

10 Su Da Quan, Chen Xue and Liu Zu Hui. 1995. The Gravity Field and Tectonics of the Nansha Islands (Dangerous Ground). Proceedings AAPG-GSM Conference 1994, Southeast Asian Basins: Oil and gas for the 21st Century, Kuala Lumpur, Malaysia, Geological Society of Malaysia, Bulletin 37, 117-123, Ed. G.H. Teh.

11 Su, Daquan and Huang Ciliu. 1987. A Study on the Gravity Field of Nansha Sea Area. Tropic Oceanology, 6 (4), 10-18.

12 --, ------, White, N. and McKenzie, D. 1989. Extension and Subsidence of the Pearl River Mouth Basin, Northern South Cina Sea. Basin Research, 2, 205-222.

13 --, -------, Liu Zuhui and Chen Xue. 1991. Gravity Field in Reed Bank and Its Vicinity, Ocean Publishing House (in Chinese).

14 Ru, KE and Pigott, J.D. 1986. Episodic Rifting and Subsidence in the South China Sea. AAPG Bull., 70, 1136-1155.

15 Srutton, R.A. 1982. Passive Continental Margins, A review of Observations and Mechanism, in R.A. Scrutton, ed., Dynamicsof Passive Margins. Geodynamics Series, 6, 5-11.

16 Sleep, N.H. 1971. Thermal Effect of the Formation of Atlantic Continental margins by Continental Break-up. Geophysical Journal of the Royal Astronomical Society, 24, 325-350

17 Kinsman, D.E. 1975. Sedimentary Histor of Trailing Continental Margin, in A.G Fisher and S. Judson, eds... Petroleum an Global Tectonics. Princeton, New Jersey Princeton University, Press, p. 83-126.

18 McKenzie, D. 1978. Some Remarks on the Development of Sedimentary Basins. Earth and Planetary Science Letters, 40, 25-32.

19 Burke, K., abd Whiteman, A.J. 1972. Uplift, Rifting and the Break-up of Afrika, in D.H. Tarling and S.K. Runcorn, eds. Implications of Continental Drift to the Earth Sciences, London, Academic Press, 2, 735-755.

20 Sleep, N.H. 1982. Thermal Contraction beneath Atlantic Margins, in R.A. Scrutton, ed. Dynamics of Passive Margins. Geodynamics Series, 6, 154-158.

21 Barr, S.M. and Mc Donald, A.S. 1981. Geochemistry and Geochronology of thelate Cenozoic Basalts of Southeast Asia. GSA Bulletin, 92, 1069-1142.

22 Wolfe, J.A. 1984. North Palawan Block, Philippines-Its Relation to Asian Mainland and Role in Evolution of South China Sea, Discussion. AAPG Bull., 68, 914-915.

23 Geological Survey of Japan. 1994. Magnetic Anomaly Map of East Asia, 1:4,000,000, Magnetic Anomaly Map 2. Geological Map of Japan.

24 Li Chun-Feng, Shi Xiaobin, Zhou Zuyi, Li Jiabiao, Geng Jianhua, and Chen Bing. 2010. Depth of to the magnetic layer bottom in the South China Sea area and their tectonic implications. Geophysical Journal International, 182, 1229-1247, doi: 10.1111/j.1365-246X.2010.04702. x.

25 Houtz, R.E. and Hayes, D.E. 1984. Seismic Reflection Data from Sunda Shelf. The AAPG Bull., 67 (12), 1870-1878.

26 Telford, W. M., Geldart, L. P., Sheriff, R. E., and Keys. D. A.1990. Applied Geophysics, Cambridge University Press, Cambridge.

27 Taylor, B. and Hayes, D.E. 1984. Origin and History of the South China Sea Basin, The Tectonic and Geologic Evolution of Southeast Asian Seas and Islands, Part 2. Geophys. Monograph, American Geophysical Union, 27, 23-56.

28 Sunata, W. dan Wahyono, H. 1998. Penerapan Metode Paleomagnet untuk Rekonstruksi Pergerakan Jangka Panjang Kalimantan, Penerapan Metode Geofisika di Indonesia, 1977-1997, Edisi Pertama. Himpunan Ahli Geofisika Indonesia (HAGI), h. 45- 54, Penyunting (editor) M. Untung.

29 Schmidtke, E., Fuller, M. and Haston, R. 1990. Paleomagnetic Data from Sarawak, Malaysian Borneo and the Late Mesozoic and Cenozoic Tectonics of Sundaland. Tectonics, 9, 123-140.

30 Haile, N.S., McElhinny M.W. and McDougall, I. 1977. Paleomagnetic data and Radiometric ages from the Cretaceous of West Kalimantan (Borneo), and their significance in Interpreting Regional Structure. J. Geo. Soc. London, 133, 133-144

31 Studies in East Asian Tectonics and Resources (SEATAR). 1980. Chapter V, Reviews of Regional Research Projects and General Recommendations, Heat Flow, CCOP Project Office.

32 Ding Weiwei, and Li Jiabiao. 2016. Propagated rifting in the Southwest sub-basin, South China Sea: insights from analogue modelling. Journal of Geodynamics, Elsevier, p. 71-86.

33 Qina Xu-wen, Zhaoa Bin, Li Fu-yuan, Zhanga Bao-jin, Wanga Hou jin, Zhanga Ru-wei, Hec Jia-xiong, and Chena Xi. 2019. Deep structural research of the South China Sea: Progresses and directions. China Geology,, p. 530-540.

34 Hall, R., and Breitfeld, H.T. 2017. Nature and demise of the Proto-South China Sea. Bulletin of the Geological Society of Malaysia, 63, 61-76.

35 Liua Siqing, Zhaoa Minghui, Sibuet Jean-Claude, Qiua Xuelin, Wuc Jonny, Zhanga Jiazheng, Chend Chuanxu, XueYa, and Suna Longtao. 2018. Geophysical constraints on the lithospheric structure in the northeastern South China Sea and its implications for the South China Sea geodynamics. Tectonophysics, 742-743, 101-119

36 Gozzard, S., Kusznir, N., Franke, D., Cullen, A., Reemst, P., and Henstra, G. 2018. South China Sea crustal thickness and oceanic lithosphere distribution from satellite gravity inversion. Petroleum Geoscience (PG),


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