Baishui Gao is a PhD student at China University of Petroleum-Beijing. He has participated in many studies on Poyang Lake and Daihai Lake.
Four typical Crevasse Splays (CS) have developed around Fuqiancun village along Xinjiang River. CS present sedimentary thickness of 0.3-2 m and reverse graded profiles. A CS includes inner fans and outer fans. An inner fan can be divided into crevasse channels and interchannel beaches. A CS evolves in three stages: the formation stage, the extension stage and the channelized stage. In the formation stage, a single fan is formed due to burst of levee; channels on CS surface are short and shallow with instable locations; the sedimentary profile shows multiple morphologies. In the extension stage, CS progradation is formed in arborization pattern; channels are deep and long, and become the framework of a CS; the sedimentary profile shows the reverse grading structure formed by the superposition of multiple single fans. In the channelized stage, most single fans are abandoned to be flood plains, and a small number of channels continue to incise and extend headward. Natural levees are formed on both sides, and sedimentary units such as point bar appears. In the stage, crevasse deltas can be formed when the channels enter alluvial lakes. Satellite images indicate that a CS grows fast during formation stage while slowly during extension and channelized stage. Paleo-CS can be identified by sedimentary scale, sediments characteristics, amplitude change of logging curve, cycle change, sand plane form, profile morphology, the coexistence with river channels and other characteristics.
G S Kazanin is the Director of Marine Arctic Geological Expedition (MAGE), Murmansk, Russia. He has published more than 50 papers in reputed journals.
The geophysical (24_channel CMP records, hydromagnetic measurements, surface gravity measurements, seismo-acoustic profiling, refraction seismic exploration) and geological (bottom sediment sampling in some areas) data obtained by geologists from the Murmansk Arctic Geological Expedition served as material for this work. In total, the CMP and seismic refraction investigations were accomplished along profiles 109 (16462 km) and 8 (3440 km), respectively. The data obtained by the gravimetric and magnetometric surveys (Scale 1: 1000000) in the southern and eastern parts of the region and by complex geological–geophysical investigations (CMP method, gravity and magnetic measurements, bottom sediment sampling) carried out south of King Karls Land on the scale 1: 200 000 were also used. In total, 31 anticlinal uplifts 1472 km2 in total and traps of the nonstructural type are defined within the undeformed Cenozoic sedimentary cover. The Paleozoic–Mesozoic sedimentary complex of the Saffolk graben includes 13 local structures 147 km2 in integral size. The traps confined to the Isfjord along_slope step and West Medvezhii shelf step and traps located within the Norwegian–Spitsbergen zone of steps are most promising with respect of hydrocarbon resources. Thus, the complex geophysical investigations with subsequent processing and interpretation of materials provide grounds for the optimistic assessment of the petroleum resource potential of the Spitsbergen continental margin. Such an assessment is supported by the following facts: (1) significant thickness of the sedimentary cover; (2) high sedimentation rate; (3) the presence of structural and nonstructural hydrocarbon traps; (4) the presumable presence of reservoirs and caps in the sedimentary section; (5) occurrence of gas hydrates in the upper part of the sedimentary section; and (6) the presence of mantle diapirs, which may serve as a catalyst for hydrocarbon maturing. Consequently, the complex investigations make it possible to elucidate a wide spectrum of aspects related to the geological structure of the Spitsbergen continental margin through its entire section, carry out its tectonic zoning, to subdivide the sedimentary cover, and to define potential objects promising with respect to hydrocarbon accumulations.