南海陆坡中新世以来沉积物特性与气体水合物分布初探

A Pilot Study on Miocene through Holocene Sediments from the Continental Slope of the South China Sea in Correlation with Possible Distribution of Gas Hydrates

通过对南海陆坡地区中新世以来沉积物的一些属性和特征的研究, 获得了下面的初步认识: (1)南海陆坡有几个沉积速率较高的地区, 如东沙一带、西沙海槽、中建南地区, 以及南沙西南部和西北部 (曾母、万安盆地 ); (2)大洋钻探钻井资料的研究表明, 中新世与早上新世为高碳酸盐比值的低速堆积期, 而近 200万a以来为低碳酸盐比值的高速堆积期, 上新世晚期至全新世沉积物以粘土质粉砂和粉砂质粘土为最主要成分; (3)南海不同时期的沉积速率不同, 全新世为沉积速率最高的时期, 其次为更新世; 上新世和中新世为沉积速率较低的时期。南海利于气体水合物存藏的沉积可能为全新世和更新世的沉积; ( 4 )对南海晚第四纪以来沉积物的综合研究表明南海陆坡的A区 (东沙附近 )、B区(西沙海槽)、D区 (南海西部、越南以东 ) 等地区可能利于气体水合物的形成和分布; 而E区 (南沙西南部 )、F区(南沙中上部) 和G区 (南沙海槽) 则是气体水合物调查值得关注的地区。

A pilot study on Miocene through Holocene sediments throughout the continental slope of the South China Sea was carried out for evaluating possible sediment regions and layers which might be suitable for distribution of gas hydrates. Among the Miocene through Holocene sediment sequences, the highest sedimentation rates were seen from the Holocene sediments, the second record occured during the Pleistocene. This result suggests Pleistocene and Holocene sediments might be better host for gas hydrates than sediments formed during other periods in the South China Sea.Four areas (Dongsha area, Xisha Trough, Zhongjiannan area and Nansha area) with high sedimentation rates were recognized, especially sediments from the first three areas are rich of (organic) carbon and contain a number of autogenetic minerals associated with gas hydrates in sediments.These (sediment) records imply that Dongsha area, Xisha Trough and Zhongjiannan area are of possible importance for (exploration) of gas hydrates.