Search

The East China Sea Shelf Basin (ECSSB) lies at the south‐eastern margin of the Eurasian Plate and was affected by the subduction of the Pacific Plate and the Philippine Plate. It experienced and recorded multistage tectonic inversions in the Cenozoic, especially in the Xihu Sag. In an attempt to investigate the evolution and mechanism of tectonic inversion, this paper presents numerical simulation results by the finite element method to the Xihu Sag. Combined with comprehensive structural analyses of seismic profiles, this paper determines the structural geometry of the sag for establishing a viscoelastic geologic model including six‐layer strata and nine major faults. Simulation results show that the boundary conditions of transtension and transpression control the inversion process that propagates from east to west, and the distribution of low compressive stress displays certain correlations with the distribution of oil deposits. Based on quantitative analysis of the vertical displacement field of the Xihu Sag, this paper identifies a tectonic inversion process, which indicates that the western part of the sag uplifts and the eastern part subsides during the first‐stage inversion; whereas the western part subsides and central‐eastern parts uplift during the second and third stages. The formation of the tectonic inversion is controlled by the adjustment of the stress field from dextral transtension to sinistral transpression caused by the change of subduction rates and direction of the Pacific Plate and the Philippine Sea Plate. [ABSTRACT FROM AUTHOR]

The East China Sea Shelf Basin (ECSSB) is a typical Meso-Cenozoic superimposed basin characterized by different tectonic frameworks, suffering multi-stage tectonism (e.g. the Indosinian, the Yanshanian and the Himalayan) since the Mesozoic. The Mesozoic ECSSB is a key place to our understanding of the tectonic evolution and dynamic mechanism in eastern South China and the subduction of the Izanagi Plate. Based on geological and geophysical results acquired over the last 10 years, this paper provides a summary of the distribution of Mesozoic strata, ascertains boundaries of the Mesozoic basin and proposes the division of the Mesozoic tectonic units in the ECSSB. The Mesozoic ECSSB was subdivided into the Western Fault Depression (WFD) characterized by dispersed Cretaceous half-grabens and the East Depression (ED) characterized by depressions at the early stage and grabens at the later stage. The WFD is composed of half-grabens formed under transtension, and the ED is composed of depression zones on the pre-Mesozoic basement under regional compression, indicating different dynamic mechanisms from the Cenozoic basins. Formation of the Mesozoic tectonic framework was controlled by the collision, compression and subduction of the Izanagi Plate and the Pacific Plate and also affected by the Indian Plate at a later stage. By comparison, this paper preliminarily proposes that the northern South China Sea and the ED of the ECSSB were originally a unified basin and jointly constituted a huge Mesozoic proto-basin in the East Asian continental margin. The Mesozoic tectonic unit division is helpful not only to discuss and resolve problems of ocean-continent differences and boundaries in southeastern South China but also to understand the tectonic nature of the East Asian continental margin, the dynamic mechanism of the Mesozoic basins and the transition of continental margin types. It also provides scientific support for petroleum exploration of the Mesozoic strata in the East China Sea. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The oil-gas accumulation process is a tectonic indicator, and the oil-gas trap is generally a result of tectonic movement. In order to explore the law of oil-gas migration and accumulation in the East China Sea Continental Shelf Basin, this paper analyses the dynamic process of hydrocarbon accumulation based on a geological model, taking the Xihu Depression as an example and using the IES PetroMod basin modelling software. Combined with the seismic data and drilling data, the burial history, thermal evolution history and hydrocarbon generation, expulsion and migration history of the Xihu Depression is simulated in this study. The simulation results show that (1) the tectonic framework of the Xihu Depression developed as an inversion structure from an early extensional stage or transtensional faulting stage to a later compressional or transpressional inversion stage; (2) the Pinghu and Huagang formations of the Xihu Depression are still currently at the peak stage of oil-gas generation, and the Xihu Depression is a depression which has abundant hydrocarbon generation and expulsion at a later stage; (3) oil-gas resources vertically migrated to the structural highs from the eastern and western sub-sags along faults and ultimately accumulated in favourable traps, which developed a migration pattern of interbedded sandstone-fault-sandstone like an upward 'staircase'. In particular, faults and the potential energy state played an important role in hydrocarbon migration of the Xihu Depression, which has a guiding significance for understanding hydrocarbon migration and accumulation law and reducing the risk in oil-gas exploration in the East China Sea Continental Shelf Basin. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Typhoons are commonly occurring disastrous events in the Western Pacific and have become more severe as the result of global climate changes, increasingly affecting the ocean and seafloor throughout the Western Pacific. However, studies on the influences of typhoon processes and dynamic mechanisms on the continental shelf remain rather limited because of insufficient observational data in the area. This paper uses observational records at a water depth of 110 m on the continental shelf of the East China Sea in the periods when the No. 1323 typhoon 'Fitow' and No. 1324 typhoon 'Danas' passed the East China Sea to study changes in the water temperature, salinity, current and turbidity. Observation results show that typhoon Fitow had limited effects on the measurement site because of the long distance to the centre of the typhoon, but during typhoon Danas, the measured surface current speed reached 2.95 m/s, and the turbidity of the sea water increased rapidly due to the vertical mixing of sea water. Typhoon Danas causes both near-inertial oscillations (NIOs) and diurnal currents to increase, which is considered to be the major factor that contributes to bottom water temperature changes and the suspension of bottom sediments after the passage of the typhoon. Typhoons can also cause the Kuroshio Current to shift towards the continental shelf, which may affect the Tsushima Current. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Based on detailed analysis of the inversion tectonics in each of the secondary tectonic units of the East China Sea Shelf Basin (ECSSB), this paper suggests that the Cenozoic positive inversion tectonics in the basin are typically anticlines of various shapes associated with thrusts. Four stages of tectonic inversions are recognized in the basin related to the Oujiang Movement (T80), the Yuquan Movement (T30), the Huagang Movement (T20) and the Longjing Movement (T12), and these four inversion stages are temporally and spatially distinct. Temporally, the tectonic inversion in the West Depression Group tended to weaken, relatively, from the Oujiang Movement (T80) to the Huagang Movement (T20), while the Longjing Movement (T12) does not show an obvious inversion signature. Spatially, the Longjing Movement tectonic inversion in the Xihu and Diaobei sags of the East Depression Group shows a pronounced reduction in intensity from north to south. The tectonic inversion in the East Depression Group tended to intensify, relatively, from the Yuquan Movement (T30), through the Huagang Movement (T20) to the Longjing Movement (T12). The intensity distribution, migration and evolution of Cenozoic inversions in the ECSSB are local responses to the synthetic effect of the convergence and subduction rates, and direction changes between the Pacific and Eurasian plates and/or between the Indian and Eurasian plates. In particular, the eastward migration of positive inversion tectonics in the ECSSB is closely and successively related to the formation of the East Depression Group and the opening of the Okinawa Trough. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The East China Sea Shelf Basin (ECSSB) is an important tectonic unit of the western Pacific active continental margin. It is divided further into a series of sags and basement ridges. The Xihu Sag on the east margin of the ECSSB is an important hydrocarbon exploration area and contains significant petroleum resources. The Huagang Formation is the major reservoir in Xihu Sag, and its provenance has been the focus of debate at all times. The major and trace elements (including rare earth elements) compositions were analyzed for the Oligocene Huagang Formation sandstone and mudstone samples in the Xihu Sag. The provenance and tectonic setting of these clastic rocks are discussed. The Chemical Index of Alteration value and A–CN–K diagrams suggest low to moderate weathering in the source areas of the Huagang Formation. The mudstones have lower index of compositional variation values (<1), indicating that the mudstone samples are compositionally mature, whereas the index of compositional variation values for the sandstone samples (0.59 to 1.87) indicate that the sandstones are compositionally immature and mature. The major and trace element composition and ratios of the clastic rock samples indicate that mudstones are mainly from Late Mesozoic igneous rocks in SE China, which is dominated by the acidic volcanic rock. The provenance of sandstones is from two different directions, the Central Uplift Group of ECSSB and the Taiwan–Sinzi Fold Belt with more mafic volcanic rock. Based on the geochemical analysis of the clastic rock samples, the tectonic setting of Xihu Sag was Japanese‐type continental margin during the Huagang Formation deposition time (Oligocene). [ABSTRACT FROM AUTHOR]

Transport and flux of suspended particulate matter (SPMs) are important but hotly debated topics in the Bohai Sea (BS), Yellow Sea (YS) and East China Sea (ECS). In this study, we calculated the sediment flux and its seasonal variation combining observed suspended sediment concentration (SSC) with numerically simulated currents. Field observations were conducted in the BS, YS and ECS at 43 stations in summer and 46 stations in winter along five transects. HYCOM/NCODA reanalysis data were used to calculate climatologically monthly averaged currents in January and July from 1998 to 2007. The results indicated that a high concentration of SPM moved out of the BS and moved southward into the YS and ECS in winter, with a net sediment flux of 0.12 t/s at the Bohai Strait and 4.37 t/s south of the Yangtze River. In summer, SSC increased from the surface to the bottom layer due to stratification. A southerly wind and stronger warm currents in summer transported SPM from the ECS to the YS and the BS, with a net northward sediment flux of 4.79 t/s at the boundary of the ECS and the YS, and a net sediment flux of 0.08 t/s input into the BS. This study can help to distinguish the contribution of the Yellow River- and Yangtze River-derived sediments to the mud-areas' generation on the continental shelves area of the Yellow Sea and East China Sea. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

It is a question whether the suspended sediment from the China continent could enter the Kuroshio Current and Pacific Ocean. Surface suspended matter (SSM) and sea surface temperature (SST) in the East China Seas from December 2009 to November 2010 has been extracted from the satellite NOAA-19 AVHRR/3. We have monitored the change of the SSM diffusion during summer half-year and winter half-year. High SSM areas occur in the inshore of the Liaodong Bay, Bohai Bay, Yellow River Delta, Shandong Peninsula, Jiangsu Coast and Yangtze Estuary, especially blooming in winter half-year. Going by our findings, the sediment provenance influences the SSM distribution, and the current system and monsoon are important factors that drive the SSM diffusion all year round. In winter half-year, the ocean colour images show that the current system is well developed. The SSMs are transported southeastward, and a part reaching the outer continental shelf is captured by the Kuroshio Current before it finally reaches the open Pacific Ocean through the Tokara Strait. Some SSMs are transported by the Yellow Sea and Tsushima Warm Current into the Yellow Sea and Japan Sea. In summer half-year, most of the SSM could not reach the continental shelf break and only little SSM could be captured by the Kuroshio Current into the open ocean. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The East China Sea Shelf Basin is an important part of the Western Pacific marginal structural domain located in the eastern margin of the Eurasian Plate. Residual sedimentary detritus in the basin has recorded much information on basin composition, plate interaction, continental dynamic environment evolution, and resource response of the Western Pacific region. For studying the Palaeogene clastic rocks obtained from the oil and gas drilling wells of the East China Sea Shelf Basin, through the rock geochemical and mineral compositional analysis, we discuss the sedimentary detritus sources, tectonic background and response to the Western Pacific continental margin tectonic environment evolution. Lithogeochemical analyses of clastic rocks suggest that Palaeocene arenites are characterized by accumulation of volcanic detritus under shallow marine depositional environments, while Eocene and Oligocene arenites are rich in inflexible quartz controlled by an oscillating coastal marine environment and metamorphic crystalline rocks of the Proterozoic Craton in South China. As geochemical compositions of the Palaeogene clastic rocks are largely unaffected by sedimentary recirculation, diagenesis, epigenesis, and chemical weathering, these rocks can be used in provenance tracing. Controlled by the combined remote effects of convergence, collision, and wedging between the Indian and Eurasian plates, and subduction, collision, and back-arc spreading between the Pacific and Eurasian plates, the East China Sea Shelf Basin showed a tectonic background of both active continental margin and continental island arc in the Palaeocene. The Palaeogene clasts of the Lishui Depression accordingly showed characteristics of recycled orogenic provenance and volcanic arc orogenic provenance, which were mainly Mesozoic volcanic rocks, volcaniclastic rocks and granites from the Zhemin Uplift and Yandang Low Bulge. Along with the Pacific subduction zone passively retreated to the west side of the ancient Ryukyu Island Arc (Diaoyu Island Uplift-Fold Belt), the source area showed mixed characteristics of recycled orogenic belt, collisional suture and folded overthrust belt, and subduction complex provenance, and the Eocene and Oligocene source rocks were mainly Proterozoic metamorphic quartzite and Mesozoic magmatic igneous rocks from the Haijiao and East Yushan uplifts. The supply of clasts by the Proterozoic cratonic metamorphic rock of South China led to a sharp increase in ancient deposits of source rocks. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]