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Yang F.,Key Laboratory of Surveying and Mapping Technology on Island and Reef | Yang F.,Shandong University of Science and Technology | Lu X.,Key Laboratory of Surveying and Mapping Technology on Island and Reef | Lu X.,Shandong University of Science and Technology | And 3 more authors.
Wuhan Daxue Xuebao (Xinxi Kexue Ban)/Geomatics and Information Science of Wuhan University

In this paper, we analyzed the characteristics of attitude errors caused by imperfect alignment of the MRU with the reference frame of vessel, and influences on the positions of beams in multibeam survey in detail. In this case, according to the rules that depth error is mainly determined by roll error, and roll error is mainly related with pitch, the 3D sun-illuminated terrain of seafloor, the math tool of Fourier or Wavelet, and the side projection of depth errors are used to confirm whether imperfect alignment of the MRU exists or not. If it exists in multibeam survey, we can obtain the offset angle when the linear relations of pitch and depth errors are disappeared. Finally, all data which are impacted by the imperfect alignment of the MRU will be corrected by the offset angle. It provides a reference for improving multibeam bathymetry, especially in shallow water. Source

Han X.,Key Laboratory of Submarine Geosciences of SOA | Li J.,Key Laboratory of Submarine Geosciences of SOA | Chu F.,Key Laboratory of Submarine Geosciences of SOA | Yang F.,Shandong University of Science and Technology

Zhujiang Submarine Canyon, a large submarine canyon, is located in the northern South China Sea, extending to 300 km southeastward from the shelf break off Zhujiang River estuary, down to deep-sea basin. Based on the full-coverage multi-beam seabed terrain data, the subtle topographic features of Zhujiang Submarine Canyon are analyzed. According to the morphology, trend, and bottom axial gradient, Zhujiang Submarine Canyon is divided into upper, middle and lower segments and deep-sea fan. On the basis of geomorphology, tectonic interpretation indicates that Zhujiang Submarine Canyon is mainly affected by the northeast-trending faulted basin and northwest-trending fault belt since Mesozoic, followed by the east-west-trending fault belt. Zhujiang Submarine Canyon maybe formed by the continuing thermal subsidence and fault depression of northern South China Sea margin caused by South China Sea spreading based on the collision between India-Australian plate and Eurasian plate. The submarine canyon becomes more narrow and deeper at the entrance because of the submarine volcanoes formed by the volcanic eruptions in Neogene. Zhujiang Submarine Canyon is continual eroded and filled by the cyclical sea level changing and massive sediment carried by Zhujiang River. The thick sediments, slump layer and developed fracture are conducive to migration, aggregation and accumulation of hydrocarbon. And the surface hydrocarbon spill formed the seabed pockmark structure on the north slope of the submarine canyon. © 2010 IEEE. Source

Lei J.,Key Laboratory of Submarine Geosciences of SOA | Lei J.,State Oceanic Administration | Lei J.,Key Laboratory of Marine Biogenetic Resources of SOA | Chu F.,Key Laboratory of Submarine Geosciences of SOA | And 9 more authors.
Earth Science Frontiers

Molecular composition of extractable and detectable organic matter in hypothermal product from 49.6°E hydrothermal vent field were analyzed by GC and GC-MS. Combined with the analysis of biomarkers and individual isotopic composition, we discussed the composition, origin and genetic implication of hydrocarbons. N-alkanes(3.437-3.962 μg/g) are the main hydrocarbon of sulfide chimney, with low L/H ratio (<1) and slight odd carbon number predominance in >C22 alkanes (CPI=1.140-1.209); NAR is close to 0. Sulfide chimney has a variety of biomarkers (Sq, IS40, cyclohexylalkanes); 22S/(R+S) of C31 hopanes achieved 0.77; 17β(H) and 21β(H)-hopanes were absent. The fatty acid of sulfide chimney is comprised of short chain saturated fatty acid and iso/anti-iso fatty acid, and lacks monounsaturated fatty acids. Iso-alkanes(2.094 μg/g)are the main hydrocarbon of hydrothermal altered rock; n-alkanes are characterized by more low carbon (L/H=1.33) and even carbon number predominance (CPI=0.377); monounsaturated fatty acids are the most abundant fatty acid. These results suggested that the autochthonous organisms were the major source of hydrocarbons in 49.6°E hydrothermal area, and that the temperature and chemical condition of hydrothermal fluid constrained the distribution of hydrothermal community and the composition of hydrocarbon of hydrothermal product. The molecular evidence for the abiogenic synthesis of organic compounds was rare, however, the coexistence of methanogens and sulfate reducing bacteria indicated that H2 were rich in hydrothermal fluids of 49.6°E vent and the abiogenic synthesis approach could not be neglected. ©, 2014, The Editorial Office of Earth Science Frontiers. All right reserved. Source

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