摘要
西太平洋 DSDP45 1孔 (18°0 0 .88′N、143°16 .5 7′E,水深 2 0 6 0 m)的微体化石群和底栖有孔虫的同位素变化揭示了研究区中新世晚期以来的古海洋学演变及其重大事件。介形类化石群由晚中新世—早上新世 (超微化石 NN11- 13/ 14带 )的 Cytheropteron组合向早上新世—第四纪 (NN15～ 2 1带 )的 K rithe组合转变及 K rithe丰度的连续上升 ,很可能指示了西马里亚纳海岭自中新世以来下沉幅度达千米左右 ,水团由早期的中层水逐渐被深层水替代。底栖有孔虫 Cibicidoides wuellerstorfiδ1 8O在 NN11带晚期至 NN12带早期急剧变轻 ,反映了中新世末期碳偏移的全球事件。在 NN12带晚期至 NN16带早期 ,δ1 8O比其现代值轻 0 .5 5‰ ,推测早—中上新世暖期时底层水温要比现代高约 2℃左右 ;介形类的新生速率大于灭绝速率指示当时为有利底栖生物的时期。 δ1 8O最急剧的转变发生在 NN16和 NN17的过渡带 (距今约 2 .5 Ma) ,增值达 1.0‰ ,并在此后保持高值 。
The microfossil and benthic foraminifera isotopic data of DSDP site 451(18°00 88′N,143°16 57′E,water depth 2 060 m)record the paleoceanographic evolution and its major events since the late Miocene.The ostracod turnover from the Cytheropteron assemblage of the late Miocene early Pliocene (nannofossil zone NN11～13/14)to the Krithe assemblage of the early Pliocene Quaternary(NN15 21)with a continuing increase of Krithe abundance probably indicates a deepening of some 1 000 m water depth and a change in water property from the Intermediate Water to the Deep Water,which may have been a result of the continuing subsidence of the West Mariana Ridge since the late Miocene.An abrupt 0 9‰ decrease in the δ 13 C of benthic foraminifera Cibicidoides wuellerstorfi during the period of the late NN11 to NN12 represents the latest Miocene carbon shift in the West Pacific that has been documented globally.In the interval between the late NN12 and early NN16,δ 18 O values are 0 55‰ lower than the modern value,inferring that the bottom water in the early middle Pliocene warm period may have been 2 ℃ higher than today.The ostracod origination is higher than its extinction in the early middle Pliocene,reflecting a favorable period for the benthic organism.The most rapid and drastic shift in δ 18 O values occurred in the transition of NN16 and NN17 with a maximum increase of 1 0‰ and then δ 18 O remains high,signaling the buildup of the Arctic ice and the beginning of the northern hemispheric glaciation.
出处
《海洋地质与第四纪地质》
CAS
CSCD
北大核心
2000年第2期51-56,共6页
Marine Geology & Quaternary Geology
基金
国家自然科学基金资助项目!( 4 96762 8
499995 60 )
关键词
微体化石
晚中新世-第四纪
同位素
古海洋学
nannofossil
late Miocene Quaternary
isotope
paleoceanography
West Pacific
