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Oxygen isotope stratigraphy and events in the northern South China Sea during the last 6 million years

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Science China Earth Sciences 2001年第10期44卷 592-960页

作者：翦知湣成鑫荣赵泉鸿王吉良汪品先 1. key laboratory of marine geology Ministry of Education Tongji University 200092 Shanghai China

Based on the stable isotopic analysis of more than 1.00 samples of planktonic and benthic foraminifers from ODP Site 1.48 in the northern South China Sea (SCS), the oxygen isotope stratigraphy has been applied to the last 3 million years for the first time in the SCS. Furthermore, the paleoceanographic changes in the northern SCS during the last 6 million years have been unraveled. The benthic foraminiferal δ1.0 record shows that before ~3.1.Ma the SCS was much more influenced by the warm intermediate water of the Pacific. The remarkable decrease in the deepwater temperature of the SCS during the period of 3.1.2.5 Ma demonstrates the formation of the Northern Hemisphere ice-sheet. However, the several sea surface temperature (SST) reductions during the early and middle Pliocene, reflected by the planktonic foraminiferal δ1.O, might be related to the ice-sheet growth in the Antarctic region. Only those stepwise and irreversible SST reductions during the period of ~2.2-0.9 Ma could be related to the formation and growth of the Northern Hemisphere ice-sheet.

关键词： oxygen Isotope stratigraphy Pliocene-Pleistocene Northern Hemisphere glaciation middle Pleistocene revolution South China Sea.

A record of Miocene carbon excursions in the South China Sea

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Science China Earth Sciences 2001年第10期44卷 943-951页

作者：赵泉鸿汪品先成鑫荣王吉良黄宝琦徐建周震翦知湣 1. key laboratory of marine geology Ministry of Education Tongji University 200092 Shanghai China

High-resolution δ1.C records are presented for the Miocene benthic foraminifers Cibici doides wuellerstorfi and C. kullenbergi (24-5 Ma) and the planktonic foraminifer Globigerinoides sacculifer (1.-5 Ma) from ODP Site 1.48A (1.° 50.1.′N, 1.6° 33.93′E, water depth 3308.3 m),northern South China Sea. The general pattern of parallel benthic and planktonic δ1.C shows a decrease trend of δ1.C values from the early-middle Miocene to the middle-late Miocene. Two dis tinct δ1.C positive excursions at 23.1.22.2 and 1..3-1..6 Ma, and two negative excursions at 1..2-9.4 and 6.9-6.2 Ma have been recognized. All these events are cosmopolitan, providing the good data for the stratigraphic correlation of the South China Sea with the global oceans as well as for studying the changes of the global carbon reservoir and its corresponding climate.

关键词： carbon isotope carbon excursion Foraminifera paleoceanography Miocene South China Sea

Exploring variations in upper ocean structure for the last 2 Ma of the Nansha area by means of calcareous nannofossils

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Science China Earth Sciences 2001年第10期44卷 905-911页

作者：刘传联成鑫荣 1. key laboratory of marine geology Ministry of Education Tongji University 200092 Shanghai China

A great number of calcareous nannofossils have been found in the deep-sea sediments of 2.32 Ma at ODP Site 1.43 located in the Nansha area, the southern South China Sea. The number of coccoliths varies from about 0.5×1.6 up to almost 53×1.6 coccoliths/g sediment, with an average of 1.×1.6 coccoliths/g sediment. The accumulation rate of total coccoliths varies from 1.1.6 to 278×1.6 coccoliths/cm2 ka. The nannofossil assemblages are usually dominated by a lower-photic species-Florisphaera profunda, of which the average percentage is about 70% in all samples. The absolute abundance and the accumulation rate of nannofossils as well as the percentage ofF. profunda display significant oscillations on two different time scales. One is the fluctuation coincident with the glacial-interglacial cycle, and the other is the long-term changes on a time scale longer than 1.0 ka. Six evolutionary stages of calcareous nannofossils could be divided for the last 2.32 Ma, from which we can reconstruct the changes in the depth of nutricline of the Nansha area. In this paper, the possible mechanism resulting in these variations is also discussed.

关键词： calcareous nannofossil nutricline upper ocean structure Nansha area

Neogene oxygen isotopic stratigraphy,ODP Site 1.48,northern South China Sea

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Science China Earth Sciences 2001年第10期44卷 934-942页

作者：赵泉鸿翦知湣王吉良成鑫荣黄宝琦徐建周震房殿勇汪品先 1. key laboratory of marine geology Ministry of Education Tongji University 200092 Shanghai China

A detailed stable isotopic study based on benthic foraminifera from 1.65 samples of ODP Site 1.48 (1.° 50.1..3’N, 1.6° 33.93’E, water depth 3308.3 m), northern South China Sea, provides an excellent oxygen isotopic record with an average resolution of 30 ka. It contains the most continuous δ1.O data with highest resolution for the whole Neogene sequence in the world. The δ1.O curve shows a step-like increasing upwards and records 5 increases, 3 decreases and 2 stable stages during the Neogene, reflecting the general trend of global cooling. Among these events the δ1.O decrease at 1..2–1..5 Ma, and two δ1.O increases at 1..5-1..6 and 3.0-2.4 Ma are most marked and globally comparable. The intervals at 1..6-1..2 and 6.0-3.0 Ma with the lowest-amplitude and least fluctuation in δ1.O represent the most stable bottom water periods for the South China Sea.

关键词： oxygen stable isotope benthic foraminifera stratigraphy paleoceanography Neogene South China Sea

Paleoceanographical records under impact of the Indian monsoon from the Bengal Deep Sea Fan and Ninetyeast Ridge during the last 260 ka

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Science China Earth Sciences 2001年第S1期44卷 351-359页

作者：方念乔陈学方丁旋胡超涌殷勇聂浩刚 1. laboratory of {1. geology China University of Geosciences 100083 Beijing China

The orbital and interior climatic cycles can be found both in the Bengal Deep Sea Fan and Ninetyeast Ridge, North Indian Ocean. The periodicity of the Quaternary glacio-eustacy by 1.0 ka gave a strong impact on the sedimentation in the fan area and the monsoon signals controlled by the obliquity and precession were easily picked up. This paper discusses the possible correlation between the environmental elements on the basis of the ETP phase wheels. A rapid change with short-periods develops during the past 60 ka in the region under study as well. The variability of paleoproductivity has a nonlinear response to the Indian summer monsoon. As contrasted to the Northwest Indian Ocean, here an abundance of Globigerina bulloides, a proxy to indicate upwelling current, does not imply so much a promotion of the summer monsoon as its decrease. The record from the ridge area shows in a longer-scale a climatic evolutionary feature corresponding to that of the fan area. A special and great event arising at around 1.5 kaBP and meaning a catastrophe for ecological environment is reported in this paper. It is also regarded as a result induced by the monsoon.

关键词： the Northeast Indian Ocean paleoceanography Indian monsoon last 260 kaBP.

Characteristic and paleoenvironmental evolution of subaerial tidal sand body in Subei coastal plain

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Science China Earth Sciences 1999年第1期42卷 52-60页

作者：李从先张家强杨守业范代读 1. laboratory of {1. geology State Education Commission 200092 Shanghai China

The subaerial tidal sand area in the northern Jiangsu Province (Subei), stretching from Dongtai towards east with a fan shape, is an early developing stage of radial sand ridges distributed in the South Yellow Sea. Since 5000–6000 a BP, after the Holocene transgression maximum in the northern Jiangsu Province, subaqueous tidal sand bodies were exposed and changed into land gradually. The environmental magnetism analysis shows that subaerial tidal sand strata are formed by the convergent-divergent paleo-tidal current field. The sediment source of tidal sand strata came early from the Changjiang River and late from the Yellow River. Sea floor erosion by tidal currents also served as an important sand source. Drilling cores and ground-penetrating profile show that there exists no probability of sand supplying directly by a large river through the apical area of tidal sand ridges either on land or in the sea. Fluvial deposits supplied the tidal sand bodies by alongshore transportation, which corresponds to the conclusions obtained by the analyses of provenance and paleocurrent field.

关键词： Subei coastal plain tidal sand bodies paleo-tidal current field paleoenvironment.

Exploring the deep South China Sea: Retrospects and prospects

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Science China Earth Sciences 2019年第10期62卷 1473-1488页

作者： Pinxian WANG Zhimin JIAN State key {1. of marine geology Tongji University

Rapid developments of deep-sea researches in China over the past 20 years have promoted the South China Sea(SCS) into the international deep-sea frontiers. The 'three deep technologies', namely scientific drilling, long-term seafloor observation and deep submersible vehicles implemented successively in SCS studies helped to achieve a number of scientific breakthroughs. Over the 20 years, five international ocean drilling expeditions to the SCS recovered nearly 1. km of sediment cores from sites at 3–4 km water depths, and drilling into the magmatic basement at 6 sites shed light on the genesis of the SCS basin. Coupled with other deep-sea short core sediments from the SCS, these records demonstrate evidence that water and carbon cycling in the low latitude regions can directly respond to the orbital forcing, and subsequently nurture a new concept of lowlatitude forcing of climate changes, which challenges the classical wisdom of the overwhelming role played by the Arctic icesheet in climate changes. The exploration in the continent-ocean transition zone also reveals a number of specific features that characterize the SCS as a marginal basin formed at the subduction zone in the Western Pacific. The features include active magmatism and rapid rupture of lithosphere through the basin formation process, and imply that 'the SCS is not a mini-Atlantic'as they can be distinguished as 'plate-edge rifting' and 'inner-plate rifting' respectively, thus challenging the universality of the Atlantic model for passive margins. Many more discoveries can be assembled from long-term mooring observations and deep diving cruises in the deep SCS, such as the cyclonic nature of the deep-water circulation, deep-water sediment transport by contour currents and turbidites, manganese nodules, extinct hydrothermal vents, and cold-water coral forests. In addition,prominent progress achieved in microbiology and biogeochemistry includes the microbial carbon pump and the coupling of carbon and ni

关键词： Deep sea Marginal sea Ocean drilling Climate change Seafloor observation South China Sea

Temporal and spatial evolution of a deep-reaching anticyclonic eddy in the South China Sea

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Science China Earth Sciences 2019年第6期62卷 1002-1023页

作者： Meng WANG Yanwei ZHANG Zhifei LIU Yulong ZHAO Jianru LI State key {1. of marine geology Tongji University

The temporal and spatial evolution of a deep-reaching anticyclonic eddy(AE) is studied using a combination of satellite measurements, moored observations and ocean model reanalysis data in the South China Sea(SCS). Three evolutionary stages in eddy's lifecycle are identified from changes in eddy dynamical characteristics estimated from satellite altimetry: birth(22 days), growth(64 days), and decay(47 days). Similar patterns are also distinguished from dynamic signals in ***, flows reversal and upwelling of cold water below 1.00 m were captured by the in-situ records when this energetic,highly nonlinear and long-lived(over 1. weeks) AE passed by our mooring position. Its detailed vertical structure is examined through temperature anomalies, vertical shear of horizontal velocities, and horizontal streamlines estimated from ocean model reanalysis data. Results from the model reveal a mesoscale AE with first-mode baroclinic structure: a bowl-shaped anticyclonic flow in the upper ocean connected to a slant-cylinder cyclonic flow at depth, with a transition layer at depths between 400 and 700 m. It is in good agreement with moored observations but showing a shallower transition depth, suggesting a slight deficiency in the model due to limited deep-sea observations. Last, we estimate eddy heat transport at different depths and stages along the AE's path based on the model data. The result reveals that pronounced heat fluxes occur during growth stage(depths 700–1.00 m).Dynamical characteristics suggest that the vertical structure and temporal evolution of the eddy play significant roles in basinscale movement and heat transferring. Considering that mesoscale eddies are ubiquitous in the SCS, our results support a recently-proposed mechanism, whereby upper ocean flows produce changes in the deep-sea circulation, potentially influencing boundary l

关键词： Deep-reaching mesoscale eddy Evolution HYCOM The South China Sea

Seasonal variability of tides in the deep northern South China Sea

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Science China Earth Sciences 2019年第4期62卷 671-683页

作者： Jiuqiang ZHAO Yanwei ZHANG Zhifei LIU Yulong ZHAO Meng WANG State key {1. of marine geology Tongji University

Tides are the major energy source for ocean mixing, regulating the variation of oceanic circulation and sediment transport in the deep sea. Here twenty months of high-resolution current profiles, which were observed via a mooring system at a water depth of 21.0 m in the northern South China Sea(SCS), are used to investigate seasonal variability in deep-sea *** analysis shows that tides in this region are dominated by diurnal tide, and both diurnal and semidiurnal tide are vertical mode-1.dominant. Baroclinic diurnal tidal current exhibits pronounced seasonal variability, showing its kinetic energy was the strongest in summer, and the maximum depth-averaged value was up to 86.7 cm^2 s^(-2), which was about 1.5 times of that in winter and twice that in spring and autumn. In contrast, baroclinic semidiurnal tide displays no evident seasonal variability. Such seasonal variability in baroclinic tide was mainly modulated by the barotropic forcing from the Luzon Strait. On the other hand,two anticyclonic eddies and one cyclonic eddy, which originated off southwestern Taiwan in winter, crossed the mooring *** cyclonic eddy had weak impact on current velocity in the deep sea, but the two deep-reaching anticyclonic eddies enhanced the current velocity through the full-water column by inducing strong subinertial flows. Consequently, the kinetic energy of tides was strengthened and the incoherent variance of baroclinic diurnal tide increased in winter, which contributed ～85% of the variability in diurnal tide. Meanwhile, the velocity of baroclinic diurnal tide was reduced in winter, which was attributed to the weakened stratification induced by the passage of anticyclonic eddies in the deep sea. The seasonal variability of tides in the deep northern SCS can provide a dynamic mechanism for interpreting sediment transport processes in the deep sea on different time scales.

关键词： Tides Seasonal variability Subinertial current Mesoscale eddy Deep northern South China Sea