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在地质部海洋地质司领导的关怀下,由海洋地质调查局和海洋地质研究所联合组成调查队,再次借用东海水产研究所《东方》号调查船,于1981年8月22日至9月15日对冲绳海槽进行第二航次地质调查.本航次调查范围涉及的地理座标为123°—129°07′E;24°26′—31°N,包括东海陆架外缘、陆坡、海槽、琉球岛坡及琉球海岭的一部分.其中,123°—127°20′E、24°26′—25°30′N之间的沉积物取样,在国内是首次进行.此次调查共完成测深线2465公里,取样站位71个,调查总面积约14万平方公里.通过调查并综合国内以往的调查资料进行分析研究后,拟将对海槽区地形地貌、底质等的新发现、新认识,扼要报导如后.1.地形地貌(1)调查过程中并未发现海槽中有大于2400米水深的海域;(2)陆坡(相当海槽西或西北坡)平均坡降为0.042,坡角为2°24′:岛坡(相当海槽东或东南坡)平均坡降为0.045,坡角为2°36′;(3)海槽的平面形态呈单个香蕉形.总体走向为北东,实际上其北段为北北东,向南逐渐过渡为南南西,呈开阔弧形,在宫古岛以北地区向东南突出.海槽槽底平均宽100公里,最窄处约60公里,最宽处位于奄美群岛西北部,可达125公里;
Under the leadership of the Department of Geology and Marine Geology Division, a survey team jointly formed by the Bureau of Marine Geological Survey and the Institute of Marine Geology re-borrowed the survey vessel “Dongfang” of the East China Sea Fisheries Research Institute from August 22 to September 15, 1981 Japan conducted a second voyage geological survey of the Okinawa Trough, covering the geographical coordinates of 123 ° -129 ° 07’E and 24 ° 26’-31 ° N, including the outer shelf of the East China Sea shelf, the slope of the continental shelf, , The Ryukyu Island slope and part of the Ryukyu Ridge, of which sediment samples between 123 ° -127 ° 20’E and 24 ° 26’-25 ° 30’N are the first in China and the survey was completed 2465 kilometers deep, 71 sampling stations, the total survey area of about 140,000 square kilometers.Through the investigation and analysis of previous domestic survey data analysis, the proposed trough area topography, sediment and other new discoveries, (1) No sea area greater than 2,400 meters in the trough was found in the survey; (2) The average slope gradient of the slope (equivalent to the west or northwest of the trough) was 0.042 , The slope angle is 2 ° 24 ’: the average gradient of island slope (equivalent to the east or southeast slope of the trough) is 0.045 and the slope angle is 2 36 ’; (3) The plane shape of the trough is a single banana shape, with its overall strike to the north east. In fact, the northern part of the trough is northeast to north and south to south gradually to the south and southwest. The area southeast to highlight the trough at the end of the average width of 100 km, the narrowest point of about 60 km, the widest point in the northwestern Amami Islands, up to 125 km;