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Li X.,Wuhan University | Li X.,CAS Qingdao Institute of Oceanology | Li X.,Key Laboratory of Submarine Geosciences | Fairweather L.,University of Aberdeen | And 9 more authors.
Journal of Asian Earth Sciences | Year: 2013

The large Miocene-aged palaeo canyon that extents through the Qiongdongnan basin (QDNB) and Yinggehai basin (YGHB) of Northern South China Sea has been of considerable interest both economically and scientifically over the past decade. Stemmed from this, significant research has been employed into understanding the mechanism for its existence, incision, and sedimentary fill, yet debate remains. In the first case the canyon itself is actually quite anomalous. Alone from the size (over 570. km in length and more than 8. km in width (Yuan et al., 2009)), which is considerably more than most ancient deep-water channels (REFS), the canyon's sedimentary fill is also distinctly different. Some explanations have been given to explain the canyon's origin and existence, these include increased sediment supply from the Red River which is genetically linked to uplift of the Tibetan Plateau, lowstand turbidite and mass-transport activity, reactivation and dextral displacement of the Red River Fault zone inducing erosive gravity-flows, regional tilt of the QDNB and YGHB, paleo-seafloor morphology and seal-level fluctuations. With the application of new data obtained from interpretations of a large number of 2D seismic profiles, core and well log data, and tectonic and sedimentary analysis this contribution aims to: (1) Present models to explain the Canyon's sedimentary fill and basin plain deposits, which provided significant understanding of processes pre-, syn- and post-incision and; (2) review the plausibility and likelihood of each of the controlling mechanisms, hoping to shed light on this controversial aspect. We conclude that the final erosive event that shaped the canyon is dated at 5.5. Ma. The Canyon's unusual fill is a product of variation in the interaction between turbidity currents and MTD that blocked the canyon's axis, and the reduction in gravity flow energy through time; and therefore the complete succession represents one major erosive and cut event at 5.5. Ma and thereafter multi-gravity currents fills unlike in most slope channel-fills. © 2012 Elsevier Ltd.

Dong Y.P.,Zhejiang University | Dong Y.P.,Research Center for Structures in Oil and Gas Bearing Basins | Shen Z.Y.,Zhejiang University | Shen Z.Y.,Research Center for Structures in Oil and Gas Bearing Basins | And 9 more authors.
Acta Petrologica Sinica | Year: 2011

The Daba Shan thrust belt has very complex structures, and could be divided into two parts by the Chengkou-Fangxian fault. The north part (North Daba Shan) is regarded as the conjunction between the Soulh Qinling Orogen and the Upper Yangtze block, while the south part (the South Daba Shan) is a typical thrust-fold belt. In this paper, we focus on the structures of the South Daba Shan thrust-fold belt. The result indicates that it has multi-level and multi-stages deformation. The upper system is controlled by detachment along the gypsum layers in the limestone of the lower Triassic Jialingjiang Formation, and nearly all the Mesozoic strata are involved into the deformation. While the lower system is confined between two detachment surfaces; The gypsum layers in the lower Triassic Jialingjiang Formation and the shale in the Sinian. We accomplish three comprehensive regional geological sections, as well as their balance restoration sections, across the South Daba Shan based on geophysical data and Field investigation. According to them, we study in detail the structure and distribution of the upper and the lower thrust systems, their geometric and kinematic characteristics, and the spatial relationship between the Daba Shan and the Chuandong thrust-fold belts. We conclude that the South Daba Shan thrust belt is a complex multi-level thin-skinned thrust system with strong deformation and shortening.

Bian G.,Troops 91550 | Bian G.,Key Laboratory of Submarine Geosciences | Bian G.,Dalian Naval Academy | Zhai G.,Naval Institute of Hydrographic Surveying and Charting | And 5 more authors.
Cehui Xuebao/Acta Geodaetica et Cartographica Sinica | Year: 2014

The properties of harmonic function are studied, and it is proved that Bm is a pseudo-harmonic function. Based on the use of stable vertical derivatives, a stable algorithm is presented to perform downward continuation applying improved Taylor series approximation. Furthermore, the problem of edge effects could be settled out using grid extension to the four directions with half a cosine function before the vertical derivative calculation. The effectiveness of the suggested algorithm has been illustrated by real magnetic data from an airborne and seaborne magnetic survey. The conclusion shows that the presented technique can be employed to perform stable downward continuation of total field magnetic data and provide better results than other techniques based on fast Fourier transformation (FFT) or on normal Talor's series or integral-iteration method when the data is noise-free, and almost the same as integral-iteration method if the data contains certain noise.

Zhao J.,State Oceanic Administration | Zhao J.,CAS Qingdao Institute of Oceanology | Feng X.,State Oceanic Administration | Shi X.,State Oceanic Administration | And 9 more authors.
Marine Pollution Bulletin | Year: 2015

Organic and inorganic sedimentary parameters in and off the Changjiang Estuary have been analyzed to reconstruct historical trends in eutrophication and hypoxia over the last century. The lipid biomarker concentrations in the Changjiang Estuary mud area (CEMA) indicated eutrophication accelerated after the 1970s. Meanwhile, Mo/Al indicated hypoxia has increased since 1960s. Eutrophication and hypoxia in the CEMA are primarily a result of the dramatically increased load of terrestrial nutrients from the Changjiang to the East China Sea. The lipid biomarker concentrations in the southwest Cheju Island mud area (SCIMA) showed primary production is controlled mainly by changes in regional climate and marine current. No significant hypoxia occurred in the SCIMA over the past century as indicated by Mo/Al. Therefore, geochemical indicators of eutrophication and hypoxia revealed different patterns between the CEMA and SCIMA, suggesting the role of river-derived nutrients in sustaining eutrophication and hypoxia in the CEMA since the 1960s. © 2015 Elsevier Ltd.

Han X.,Key Laboratory of Submarine Geosciences | Han X.,State Oceanic Administration | Shi J.,Ocean University of China | Zheng M.,State Oceanic Administration | And 8 more authors.
OCEANS 2013 MTS/IEEE - San Diego: An Ocean in Common | Year: 2013

During Younger Dryas period (12.9∼11.6 cal. ka), the sea level oscillates at about -66m depth contour in the continental shelf seas in eastern China and the seawater gets into the south of present North Yellow Sea. So Yellow Sea became a long narrow channel gulf. To simulate the tidal current of this special gulf, Environmental Fluid Dynamics Computer Code (EFDC) was used in this paper. The calculation combines curvilinear orthogonal coordinates in the horizontal direction with Sigma mapping coordinates in the vertical direction, and it uses a method which transforms a problem from three-dimensional into two-dimensional. The results show that the tidal current is still very strong in Yellow Sea during Younger Dryas period, entering the special gulf along the right side entrance. From shallow both sides to deep centre, rotating flow changes reciprocating flow. Under the effect of reciprocating flow, the floor is eroded and the mud and sand are carried away. Progressive wave turns into rotating wave and two ateliotic amphidromic points appear on the western side of the gulf after tidal wave coming into Yellow Sea. At the same time, the tidal residual current flows towards southeast and east at relatively high velocity while at the west and interior gulf and it becomes weak near the entrance. The current may carry the bottom sediment and discharges them at the location of present mud sediment zone in north East China Sea. But at eastern Yellow Sea the tidal residual current flows to north and forms an anticlockwise circulation at centre of the eastern gulf which is corresponding to the eddy mud zone in Southeast Yellow Sea. The anticlockwise circulation captures suspended sediment and may gestate the present mud sediment zone. The extension direction of tidal sand ridges and the size composition of the tidal current sand in East South Yellow Sea have a close relationship with the tidal current field of the ancient Yellow Sea, so the fluctuating lesser sea level changing and the relative stable tidal current field are the favorable factors for the tidal sand ridges during Younger Dryas Episode in ancient Yellow Sea. It can be said that the ocean current, tidal current and tidal residual current figure the pattern of present Yellow Sea during Younger Dryas Period. © 2013 MTS.

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