Heinrich event imprints in the Okinawa Trough: evidence from oxygen isotope and planktonic foraminifera

Planktonic foraminiferal faunas, oxygen isotope and modern analog technique sea surface temperature records were obtained in piston core DGKS9603 (28degrees08.869'N, 127degrees16.238'E, water depth 1100 in) collected from the middle Okinawa Trough. During the last glaciation, four cold events were identified and correlate Heinrich events (HE) H2-5 of the last 45 ka. During the last deglaciation, core DGKS9603 has begun to be influenced by the Kuroshio since about 16 cal ka BP. Three weakenings of this warm current occurred at about 2.8-5.3, 11.4 and 15.5 cal ka BP respectively. Among the three fluctuations, the oldest one is synchronous with HE1 and could be a response to the strong cooling observed in the North Atlantic Ocean. The fluctuation occurring at about 11.4 cal ka ago corresponds to the Younger Dryas within the age error bars. Our observations provide new evidence that the HEs documented from Greenland and the northern North Atlantic had a global climatic impact. Changes in the intensity of the East Asian monsoon could be the main mechanism responsible for the paleoccanographic variations observed in the Okinawa Trough. (C) 2001 Elsevier Science B.V. All rights reserved.

南海沉积物中的放射虫及其古环境意义

In this paper a systematic study of radiolarian from surface sediments of all the South China Sea (SCS) has initially been done for its deposit ecology, biogeography and paleoenvironment significance. The paleoenvironment information obtained by radiolarian analysis and other sedimentary method for core samples is also made use as the synthesis proxy for revealing the paleoenvironment changes in the SCS and the relations of it with the past globe change during last 200ka. Some results come out of this study as: 1) Radiolarian skeleton chemistry composition and skeleton morphological features were analyzed, chiefly dividing them as 15 types of basic morphological features: 2) Analysis of biogeographical feature demonstrates that the fauna in SCS obviously belonging to a transitional type of west Pacific - Indian Ocean and has a particularity of itself: 3) Tendency of radiolarian population distribution is lower in shallow continental shelf area, increasing gradually toward the abyssal region; 4) Nine character boundaries of radiolarian depth distribution in the sediments from whole the South China Sea may be recognized; 5)Two radiolarian transfer functions for paleotemperature and paleo-primary productivity in the South China Sea have also been established respectively. The equation of transfer function for winter paleotemperature has only an average estimated error of 0.18678 ℃ and the equation for paleo-primary productivity has the calculation accuracy of 85.31%; 6) Changes of radiolarian individuals, numbers of species and H(S) values in core NS93-5 show the completely different oceanic geographical circumstance and ecology structure in the Last Maximum Glacial with present; 7) The abundance variation of some raiolarian warm species and cold species indicate the changes of water masse features along with the paleoenvironment evolution, showing that this sea area clearly is controlled in 6 issues of oxygen isotopes by the cold water masses; 8) By comparative analysis of δ ~(18)O curves with GISP2;s ice core can core 17940 of the northern SCS, the occurring characters of D/O's events 1-21 and Heinrich's events H1-H6 have been revealed in this sea area by core NS93-5, which prove the existence of paleoclimatic tele-connections between the southern SCS and Arctic region since about 200ka BP.