钙质成岩作用对有孔虫氧同位素的影响  

DIAGENETIC INFLUENCE ON THE FORAMINIFERAL OXYGEN ISOTOPE RECORD

作　　者：房殿勇[1] 赵泉鸿[2] 成鑫荣[2] 关平[1] 李洋冰 

机构地区：[1]北京大学地球与空间学院 [2]同济大学教育部海洋地质重点实验室,上海200092 [3]中国海洋石油渤海研究院,天津300452

出　　处：《海洋地质与第四纪地质》2005年第2期63-66,共4页Marine Geology & Quaternary Geology

基　　金：国家自然科学基金重大项目(49999560);国家重点基础研究发展规划项目(G2000078500)

摘　　要：通过对南海北部ODP184航次1148站井深477m之下深海相渐新世浮游有孔虫Globoquadrina baromoenensis压扁壳、次生方解石和充填壳的氧同位素对比,定量分析了钙质成岩作用对壳体氧同位素的影响,结果发现,受成岩作用影响,1148站浮游有孔虫氧同位素显著变轻,这种变化趋势与低纬度开放性大洋明显不同。其原因可能与南海海盆扩张早期,大量陆源物质从较窄陆架可以直接沉积到海底,由于陆源物质氧同位素相对偏负,当与海洋沉积物混合后,引起本区沉积物孔隙水氧离子浓度变轻。而扩张初始,高的沉积速率可能使钙质壳体被快速封存在一个相对孤立的系统中,造成孔隙水离子成为影响壳体氧同位素变化的主要因素。当氧同位素相对较18重的有孔虫壳体溶解和重结晶并与孔隙水离子发生交换时,引起壳体δ18O负向偏移。Three types (compressed, filled and infilling) of planktonic foraminifera G. baromoenensis tests were picked up from Oligocene sediments at ODP site 1148 (18°50.17′N, 116°33.94′E, at a water depth of 3 294 m, core depth below 477 m), for understanding the diagenetic effects on stable oxygen isotope quantitatively. The result shows the negative shifts of foraminiferal oxygen isotope during Oligocene at Site 1148 due to diagenesis. It is opposite to the diagenetic effect in the low latitude open sea, which resulted in positive δ^(18)O shifts. This difference may be ascribed to the vast amounts of terrestrial material directly from narrow continental shelf, deposited on the sea bottom during the Oligocene incipient spreading of the South China Sea basin, causing a decrease in pore-water δ^(18)O of the bottom sediments. A relative isolation system for calcareous tests may have been made by the high sedimentation rate during the incipient spreading of the basin, in which dissolution and recrystallization allow oxygen to be exchanged between the low δ^(18)O terrestrial materials and the high δ^(18)O foraminiferal tests, causing the decrease of the foraminiferal (δ^(18)O.)

关 键 词：氧同位素 成岩作用 钙质 浮游有孔虫 陆源物质 次生方解石 海洋沉积物 有孔虫壳体 Δ^18O 孔隙水 南海北部 定量分析 变化趋势 南海海盆 离子浓度 沉积速率 渐新世 深海相 开放性 低纬度 重结晶 扩张 航次 大洋 海底 陆架 

分 类 号：P532[天文地球—古生物学与地层学] P618.130.2[天文地球—地质学]