In 1975 an acoustic survey was carried out in the shallow region of the northern part of South China Sea. During the investigation, sidescanning sonar, bathymeter and sampler were used.The side-scanning sonar system operated at 150KHZ frequency, puise length is at a rate of 0.1 PPS and the grazing angle, horizontal is about 1°, vertical about 35°. The sonar grazing range is in 100 m on each side of the ship’s track. Generally, the ship’s speed is of 5 knot.Basing upon the interpretation of sonargraphic records, the results are summarized as follows:1. A submarine geomorphologic and sedimentary map has been compiled at a scale of 1:500000. On this map, three main geomorphologic areas are divided, i.e. area Ⅰ, Ⅱ, and Ⅲ. In the southern area Ⅰ. the seabed is consisted of coral limestone, barrier reef, small channels and coral pinnacles as well as central lowland on coral tableland. The coral tableland extends seaward from 5 to 10 km in distance. Two submarine terraces have been found at depth of 15 m and 19-20 m. In area Ⅱ, the seabed is in the form of a broad sandwave field in which the different type of sand wave (single and multiple), sand dune, sand bar or sands has a wide distribution. The basaltic tableland, submerged valley, submarine fan and bar have been also here found. However, some trench on more large scale from northeast to southwest are only observed in the southern area Ⅱ. As to the area Ⅲ, it is a wide submarine plain spreading seaward from 10 km to more 45 km with an average slope 0°05’.2. The finding of two submarine terraces and an ancient second shore zone at a depth about 50-60 m probably indicates the three stages of changes of sea level 7000 year ago.3. Since the 1800 year before present the sea level has a tendency of descending, while in the last 800 year it appears especially remarkable, and with a greater amplitude than that in any regions of world.
. 1978, 据地貌声图判读研究海底地貌和底质类型. 地质科学, 13(4): 373-382.
. A STUDY OF BOTTOM GEOMORPHOLOGY AND SUBMARINE SEDIMENTS BY SONARGRAPHIC INTERPRETATION[J]. Chinese Journal of Geology, 1978, 13(4): 373-382.