北海—涠洲岛海底地形地貌特征及成因分析

文章介绍通过侧扫声呐仪器对海底的扫描,结合测深数据、表层样品测试结果,以及该区地质和物探资料,描述北海—涠洲岛海底地形地貌特征,分析该海区海底地貌成因。

海洋地球科学和海洋海底测绘在地质及其它领域的应用

卫星测量等方法有助于更好地了解和测绘海洋，但解决海底测绘时穿透水体等困难的真正技术革命，反而是35年前的多波束测深系统。目前的第三代多波束测深系统能够提供海底地貌的形状、特征和水深等基本信息。因此，各国的水文或地质调查机构开展了勘探各自专属经济区的雄伟计划。此外，通过对三维地震资料的处理可以创建陆坡坡度、粗糙度、地貌类型等属性。这些属性特征有助于了解海底地貌特征，

南海北部陆坡海底异常地貌特征与天然气水合物的关系

在南海北部陆坡的浅层剖面上，发现存在若干海底声学异常反射现象，主要有滑塌体、丘状体、麻坑、羽状流(海水中)等类型，它们是由于滑塌、浅层气或流体溢出等因素造成的海底微地形地貌突变，可能与海底下存在的天然气水合物有关。

南海北部海底微地貌特征与近代变化

根据大量测深和旁侧声纳资料,对南海北部海底微地貌特征进行了分析,并探讨了近代微地貌动态变化。滨海地貌主要有河口港湾、水下浅滩、水下岸坡、水下三角洲、潮流三角洲海底沙波、潮流沙脊、海釜等;内陆架地貌主要有陆架堆积平原、水下阶地、古海岸线、古河道、小丘和坑洼群等;外陆架地貌主要有陆架平原、古浅滩、古三角洲、浅槽、沙波、沙丘、埋藏古河道海底滑坡等等残留地貌滨海地区水动力作用强,加上人为因素,地貌形态变化较大,内陆架和外陆架水动力作用较弱。

基于数学形态学的侧扫声呐图像轮廓自动提取

侧扫声呐图像特征自动提取的难点在于特征地貌边缘检测较困难,依据图像灰度突变检测得到的边缘比较粗糙、不连续,而且有断口和小洞。本文在对图像进行预处理和阈值化的基础上,采用数学形态学方法对图像进行处理,即用具有一定形态的结构元素去量度和提取图像中的对应形状,得到连续化、粗化、圆滑的特征区域边缘填充目标内部阴影且消除背景噪声。基于数学形态学的侧扫声呐图像特征自动提取的主要步骤为:首先对侧扫声呐图像进行预处理,然后进行灰度阈值化,接着采用数学形态学方法进行处理,最后对处理后的图像进行边缘检测,提取出特征地貌边缘。实验表明,采用数学形态学方法进行处理后,错断、离散的海底目标物变得连续,背景噪声大大减少,自动提取结果准确可靠。

麦哲伦海山区平顶山钴结壳的产出条件、分布规律和形成特点

在地质、地球物理区域调查和普查所获大量实际资料基础上。探讨了麦哲伦海山区海底地貌特征、最大含矿平顶山的参效、山顶深度等。指出水文和水化学环境对钴锰结壳形成以及基质、生物和其它因素在成矿过程中的作用。分析了麦哲伦平顶山矿田内钴锰结核空间分布的区域性规律与局部规律。

Coral community dynamics and shallow-water carbonate deposition of the reef-flat around Yongxing Island, the Xisha Islands

Microbes and microbial carbonates in reef-flat and coral community dynamics and submarine geomorphologic features in reef crest and fore reef of Yongxing Island,the Xisha Islands,South China Sea,were studied by means of scuba diving,underwater investigation,and line intercept transect survey.Studies indicate a very high coral mortality with few living corals in the reef flat of Yongxing Island.Moreover,macro algae,sea grass and cyanobacteria are common in reef flat.Microbes and microbially induced carbonates occur in reef flat.Living corals grow mainly in the reef crest and fore reef,but are also declined dramatically.From coast to off shore,the southeast reef flat of Yongxing Island can be divided into beach,inner reef flat,outer reef flat,reef flat front(reef crest and fore reef),and fore-reef slope settings.Sedimentary facies include coast,reef flat,reef crest and fore reef,and fore-reef slope.Reefal carbonate sediments are composed of coral skeletons and framework,coral fragments,bioclasts,and lime mud.With the deterioration of environment and water quality,the coral communities tend to be distributed in the reef crest and fore reef with clean sea water,well circulation and moderate water energy.Reef flat is occupied mainly by the macro algae and Heliopora coerulea communities.The coverage statistics on the reef crest demonstrate that the coverage of Acropora cytherea is more than 28% and represents a dominant species with wave-resistant ecological type.Sedimentary characteristics and geomorphologic features are different between the southeast and northwest reef-flat fronts(reef crest and fore reef) of Yongxing Island.The former shows discontinuously tidal channels in outer reef flat and different dimensional and deep reef ponds in reef crest and fore reef,and the latter presents a typical spur-and-groove system.Microbes(cyanobacteria Lyngbya sp.) occur generally in the inner reef flat and reef ponds of reef crest with restricted water circulation.Widely algae growth indicates a eutrophic environment,and the common microbes on the coral surface in the reef flat and reef ponds also demonstrate eutrophication in seawater and deteriorated water quality.