西太平洋边缘海的冰期碳酸盐旋回

GLACIAL CARBONATE CYCLES IN WESTERN PACIFIC MARGINAL SEAS

碳酸盐旋回是更新世深海沉积最显著的特征。西太平洋边缘海沉积中碳酸盐含量的时空变化尤为强烈，所含深水化学、表层生产力和汇水盆地风化作用的信息也格外丰富。对鄂霍次克海、日本海、东海、南海和苏禄海等五个边缘海表层沉积中的碳酸盐分布和冰期碳酸盐旋回进行了比较。总的看来，较深水区（水深＞２００ｍ）的ＣａＣＯ３％在高纬海区甚低，而向较低纬海盆增多，显示出碳酸盐百分比与水温和水深的密切关系。西太平洋边缘海至少可区分出四类不同的碳酸盐旋回，即：西北太平洋型，日本海型，大西洋型和太平洋型，每个类型都蕴含着丰富的陆地和海洋环境信号。进一步的分析可以看出，碳酸盐旋回的不同类型取决于各个海盆深层水的来源和性质，而后者又决定于海盆的形态特征。较低纬度海区之所以存在两类不同的碳酸盐旋回，是由于控制碳酸盐相对含量的三项因素（碳酸盐生产力、深海溶解作用和非碳酸盐成分的稀释作用）在溶跃层上下的组合不同。从碳酸盐的保存和溶解指标看来，上述低纬边缘海的深海化学旋回仍属“太平洋型”，只是由于生产力和稀释作用的缘故才在溶跃层以上呈现像“大西洋型”的旋回。

オarbonate cycle is the most prominent feature in deepsea sediments of the Pleistocene.The temporal and spatial variations of carbonate content in sediments are very significant in the Western Pacific marginal seas and are particularly informative in terms of deepwater chemistry,surface productivity and weathering conditions in the drainage basins.In the present paper,the carbonate distribution in surface sediments and the glacial carbonate cycles are compared between five marginal seas:the Sea of Okhotsk,the Sea of Japan,the East China Sea,the South China Sea and the Sulu Sea.In general,CaCO3% in deep water sediments(>200m w.d.)is extremely low in the highlatitude seas and increases towards the low latitude basins(Fig.1a),revealing a close relationship between carbonate percentage and water temperature and water depth(Fig.1b).At least four types of carbonate cycles can be distinguished in the Western Pacific marginal seas:the Northwestern Pacific type (Fig.2A;Fig.3A),the Japan Sea type(Fig.2B;Fig.3B),the Atlantic type (Fig.2 C,E and D SCS15A;Fig.3C),and the Pacific type(Fig.2D SO5029KL;Fig.3D),and each of those embodies rich environmental signals both from land and sea.As shown by more detailed analyses,the variety of carbonate cycle types is largely dictated by the origin and characteristics of the deep waters of the individual sea basins which in turn depend on the basin morphology.The existence of two different types of carbonate cycles in lowlatitude seas is explained by different combinations below and above lysocline of the three controlling factors:carbonate production,deepsea dissolution and dilution by noncarbonate components.Judging from the carbonate preservation and dissolution indices,the cycle of deep water chemistry in the marginal seas in question is of “Pacific type”,whereas the apparent “Atlantic type”above lysocline is ascribed to the effect of production and dilution(Fig.4).