South China Sea Platform and South China Ocean Basin - Essay Example

South China Sea Platform and South China Ocean Basin South China Sea Platform and South China Ocean Basin Introduction South China Sea Platform and South China Ocean Basin is a region that stretches from the strait of Taiwan to the northeast up to the Strait of Malacca and Singapore in the Southwest. The basin also includes hundreds of tiny islands, reefs and rocks most of which are located around Stratly and Paracel island chains. Generally, the entire South China Ocean Basin is not only considered a critical world trade route but is also a strategically important geopolitical region due to its rich hydrocarbon resources and the historical completing claims of its ownership by several bordering countries (Bateman and Emmers, 2009). Geologically, the nearly 3.5 million square kilometers area is primarily surrounded by a series of sedimentary successions which are highly rich in petroleum resources (IHO, 1998). According to many experts, South China Sea platform and ocean basin has a complex geologic structure comprised of folded fundament dating back to the pre-Cambrian period, Indo-china period and Herynina periods. The rhomboid shaped marine basin is largely confined by crustal structure fractures, lithospheres as well as massive tectonic belts. This paper presents the history of the South China Sea basin including its stratigraphic columns and dissects as well as the history of its deposition. Summary of the Stratigraphic Columns for the Basin South China Sea basin is locacated at a junction of three major tectonics namely; the Eurasian,Pacific-philippine and the India-Australian plates. The basin lies on top of a continental self that was drowned during the ice age. According to many experts, the oceanic as well as the stretched continental crusts that are presently underlying the South China Sea basin have always experienced a series of tectonic movements since the Cenzoic times. The basin is located within the juncture area of the Indo-Australian, Eurasian and Pacific plates and the Regional Plate Tectonic events have played crucial roles to control the formation plus evolution of continental marginal basins. It is widely speculated that the basin may have been formed by underlain by continental crust before it was affected by rifting and subsequently overprinted by forearc structural setting after the initiation of subduction. For example, the evolution of the region may have been as a result of a collusion of the Eurasian and Indian plates, the northward drifting of the Australian plate as well as the westward subdution of the Pacific continental plate during the Cenozoic period as shown in figure 1 below. Fig 1: Subduction and Crustal Extension of the South China Sea Basin With regard to its crustal structure, the basement of the basin is deselected by a series of faults and overlying stratified sedimentary depositions. Moreover, unique kinds of Cenozoic continental basins and margins developed here based on the varied boundary conditions and special tectonic position. Fig 2: Crustal Stratigraphy of the South China Sea Basin (Source: U.S. Geological Survey. Fact Sheet 2010–3014) Fig 3: Inner arc islands of the South China Sea Basin (Source: U.S. Geological Survey. Fact Sheet 2010–3014) History of the Deposition The history of the South China Sea basin has primarily been constructed based on the current geophysical data as well as evidence from the geological study of the deep sea sediments. Generally, the basin forms part of the non back-arc basins that have evolved via normal processes of rifting and spreading. It is bounded to the south and north by passive continental margins and its evolution can be linked to that of any small ocean basin of Atlantic type Wang (2009) argue that the trench came into existence when the oceanic crust of South China Basin started sinking below the Philippine Sea plate while mentioning that the process has never stopped to date causing frequent quakes. Throughout the history deposition in the South China Sea basin has always been characterized by a fairly complex interplay of various lithospheric deformation and sedimentation. In relation to the tectonic of both the China Sea Platform and South China Ocean Basin the west Natuna Basin is bounded by Khorat Swell in the nothern part. The Khorat Swell south-dips with its high monoclined basement providing a wider geographical area for oil-gas deposition. The South China Sea borders Sunda Shelf to the East by Natuna Arch. To the North-West it links to the NW-SE elongated Malay Basin. The other geological structures in the South China Basin include: Nothern Central High, Southern Central High, South kakap Graben and Anambas Graben. Sundaland is the representation of the stable continental core of the South East Asia that cratonised and formed during the late Triassic time. During this period Cretaceous in the Eastern part of Sundaland reconstructed with the pacific plates in the East thus forming a zone of subduction The deformations and depositions particularly included numerous large scale lateral movements, intra plate subduction or thrusting, sea floor spreading as well as lithospheric rifting. Generally, these geological activities have critically contributed to the deposition in the basin including the presence of petroleum systems throughout the South China. The older portion of the basin is believed to feature thick sediments of about 1 to 2.5 km and smoother oceanic basements whereas the younger central part is characterized by thinner sediments ranging from 300m – 1km along with blocky basement fabric. However, its structural and depositional evolution particularly within the deep slope zone remains controversial. The evolution of the formation and deposition of the South China Sea Basin is broadly categorized into three main stages namely the early paleogene(pre-spreading/rifting stage), late paleogene/early niocene) and late miocene(post spreading stage) (CGS, 2004). Fig 2: Stages of Deposition in the South China Sea Basin During the pre-spreading stage in the early paleogene period, large scale rifting and extension took place in the region and this may have further reshaped the basin particularly with regard to its Northern margin. The extension that occurred around 30 million years ago culminated into seafloor spreading thereby resulting into the current South China Sea basin. In the early Paleogene period, the deposits that filled the South China Sea Platform and South China Ocean Basin primarily consisted of non-marine deposits of Paleogene age. The resulting rift basins later become the major sources hydrocarbon resources in the basin. Although many of the rift basins failed after the Paleogene period, a few of the rifts managed to develop further through seafloor spreading. Towards the late Paleogene period, the marine basin of the South China Sea began to be filled with a rapid accumulation of bathyla deposits which eventually developed into marine sediments due to occasional transgressions during this initial stage. The second stage witnessed significant seafloor spreading due to increased crustal thermal variations within the basin as well as increasing slab pull of the plate tectonics. The early seafloor spreading during the late paleogene/early niocene period was largely characterized by high rates of sedimentation. This was later followed by active tectonic regimes attributed to a major ridge jump towards the southwest of the basin as well as the southern extrusion forces of Indochina. Numerous geochemical analyses have indicated a significant increase in tectonic deformations during the basin formation of the South China Sea (Wang and Qianyu, 2009). On the other hand, sediment changes also took place due to increased tectonic activities which may have resulted in diagenetic overprinting on the fossil remnants within the basin. The final stage of the deposition in the South China Basin is widely known as the late Miocene or Post-spreading stage. This period was particularly marked by successive blocking of the basin with a series of island arcs resulting from the collision between Asia-Australia tectonic plates in the South. Subsequent collisions contributed to the formation of Taiwan Island and the present day Bashi Strait as well as further deposition of benthic fauna and increased sill depth. Economic Significance of the Basin According to recent estimates by the US geological survey (USG, 2010) South China Sea Platform and South China Ocean Basin has approximately 11Billion barrels of oil and 6cubic feet of gas in probable reserves (Hall, 2002). Although most of the contested areas of the basin such as Paracel islands do not have significant proven hydrocarbon resources, the disputed territories are widely believed to contain vast natural gas resources which are yet to be explored. Oil and gas normally accumulate at the continental margins at which rifting takes place though there is difficulty establishing the quantity of natural gas and oil within SCS because of territorial disputes and under-exploration. Where as national oil company can successfully extract hydrocarbons nearing the shorelines of SCS, a vast section of the site impedes development. Conclusion In conclusion, South China Sea basin is a vast region surrounded by a series of sedimentary successions which are highly rich in petroleum resources. The geological history of the South East Asian basin dates back to the pre-Cambrian period, Indo-china period and Herynina periods. Today, the South China basin is considered to be a strategically important geopolitical region due to its rich hydrocarbon resources, territorial disputes as well as by the virtue of being an important global trade route. References Bateman, Sam., Emmers, Ralf. (2009). Security and International Politics in the South China Sea: Towards a Cooperative Management Regime. New York: Routledge.  This is an exciting book that comprehensively explores both the security and international politics in the South China Sea as well as the emerging challenges of resource management in the region. China Geological Survey (CGS).(2004). South China Sea Continental Margin: Geological Methane Budget. GEOMAR Report Vol. 4 The publication highlights a number of new discoveries regarding the South China Sea Continental Margin and the current potential hydrocarbon resource in the region. Hall, Robert. (2002). Cenozoic geological and plate tectonic evolution of SE Asia and the SW Pacific: computer-based reconstructions, model and animations. J. Asian Earth Sciences, 20, 353-431. Authored by Robert Hall, the article effectively presents a plate tectonic model and theory for the Cenozoic development of the South China Sea Basin. International Hydrographic Bureau. (April, 1998). IHO Standards for Hydrographic Surveys. 4th . Edition, April 1998. Special Publication No. 44. An important publication that highlights one of the major standards developed by the International Hydrographic organization that sought to ensure that the worlds oceans, seas and national waters are properly surveyed and charted. U.S. Geological Survey. Fact Sheet 2010–3014. (March 2010). World Petroleum Resources Project. Assessment of Undiscovered  oil and gas resources in the South China Sea Basin. This fact sheet is one of the most comprehensive primary sources of detailed estimates of recoverable hydrocarbon resources in the South China Sea Basin. Wang, Pinxian., Qianyu Li. (2009). The South China Sea: Paleoceanography and Sedimentology. Dordrecht: Springer. The book offers a well balanced and all round synthesis of paleoceanography, sedimentary geology as well as sequence stratigraphy of the South China Sea Basin. APPENDIX A: Geological maps South China Sea(Source: International Hydrographic Bureau) Paleogeography map of the South China Sea Basin Hydrocarbon resource distribution in the South China Sea Basin Read More