LARGE SAND DUNES ON SUBAQUEOUS DELTA OF MEKONG RIVER, SOUTH CHINA SEA
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摘要: 根据2003和2004年冬季风之后的2次侧扫声呐调查结果,解释了湄公河水下三角洲上5个区85个水下大沙丘。沙丘尺度,高1.4~13.2 m,长72~672 m的属于Ashley (1990)分类的大和特大水下沙丘。沙丘普遍具有不对称的外形,陡坡指向W—SW。南海冬季季风引起的冬季环流汇同黑潮(分支)逆流是塑造沙丘的主要动力,据实测,金兰湾外冬季环流表层流速达1 ~1.4 m/s。水下沙丘形成于冰消期低海面时期,如今仍然顺南海冬季环流西侧自N向W—SW迁移,沙丘迁移速率约为2.78×10-5 m/s量级(按流速1.1 m/s计算)。Abstract: Eighty-five subaqueous large sand dunes were found in five areas on the Mekong river subaqueous delta by the side scan sonar investigations after the winter monsoon in 2003 and 2004. The duns are 1.4 m to 13.2 m high and 72 m to 672 m long. According to Ashley’s classification, they are large and very large subaqueous dunes. These dunes are generally asymmetric in shape with steep slopes dipping to W-WS. Water circulation induced by winter monsoon together with the reverse Kuroshio (branch) current in the South China Sea is the major driving force to the formation of dunes. Observation shows that the surface current velocity of winter monsoon circulation in the Cam Ranh Bay ranges from 1m/s to 1.4 m/s and the subaqueous dunes were formed during the low sea-level period of the last deglaciation. At present they are still migrating along the west side of the South China Sea under the winter circulation from N to W-SW and the migration velocity is in a dimension of 2.78×10-5 m/s.>
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