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| Yu, Ef; Liang, Ch; Chen, Mt. |
| Anomalously high uranium contents and U-238/Th-232 activity ratios deposited during the oxygen isotope stages 2 to 4 are observed in the MD962085 core from the Benguela Current upwelling area. In conjunction,vith the activity ratio of U-234/U-238, the high uranium contents found in this core cannot be considered as detrital; instead, they must be of authigenic origin. The high biological productivity in the overlying seawater may have induced a high flux of organic matter resulting, directly or indirectly, in a reducing environment, and may have led to the addition of authigenic uranium to the sediments during the last glacial period. The correspondence between the variations in authigenic U content, %TOC, and Th-230(ex)-normalized TOC flux supports this... |
| Tipo: Text |
Palavras-chave: Authigenic uranium; Last glacial stage; Benguela Current upwelling. |
| Ano: 1999 |
URL: https://archimer.ifremer.fr/doc/00239/35071/34562.pdf |
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| Chang, Yp; Wu, Sm; Wei, Ky; Murayama, M; Kawahata, H; Chen, Mt. |
| Biogenic carbonate and organic carbon content of two deep sea cores (MD012404 and ODP site 1202) are measured to reconstruct surface ocean productivity variations in areas of the Okinawa Trough in the Western Pacific where the modern climate is highly sensitive to the East Asian monsoon and precipitation/river runoff. Based on foraminiferal isotope stratigraphy and AMS C-14 dating, the age models of the cores indicate that core MD012404 shows relatively low sedimentation rates with 50 cm ky(-1) on average, and that the sedimentation rates in core ODP 1202 are extremely high with an average of 500 cm ky(-1). Total organic carbon (TOC) and carbonate contents in core ODP 1202 are 0.56% and 6.80% on average, respectively, and are 0.62% and 15.86%,... |
| Tipo: Text |
Palavras-chave: IMAGES; ODP; Total organic carbon; Calcium carbonate; Okinawa Trough; Paleoceanography; Climate change; East Asian monsoon. |
| Ano: 2005 |
URL: https://archimer.ifremer.fr/doc/00229/34064/32627.pdf |
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| Chen, Yy; Chen, Mt; Fang, Ts. |
| Ultrahigh resolution records of carbonate and organic carbon concentrations from core MD972148 (19 degrees 47.804'N 117 degrees 32.56'E; water depth 2830 m) provide information on glacial-interglacial as well as millennial to centennial scale variability in the production of biogenic sediments in the northern slope of the South China Sea (SCS) over the past 150,000 years. A preliminary age model of this record is estimated using a biostratigraphic datum of Globigerinoides ruber (pink) and the relationship of carbonate concentrations and partial derivative(18)O of planktonic foraminifers shown in previous SCS records. The downcore patterns in this record show that the carbonate concentration maxima correspond to interglacial times and minima correspond to... |
| Tipo: Text |
Palavras-chave: Paleoceanography; Late Quaternary; Carbonate sedimentology; South China Sea. |
| Ano: 1999 |
URL: https://archimer.ifremer.fr/doc/00239/35072/34559.pdf |
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| Kienast, M; Higginson, Mj; Mollenhauer, G; Eglinton, Ti; Chen, Mt; Calvert, Se. |
| The bulk sedimentary nitrogen isotopic composition of two cores from nearby sites on the northern slope of the South China Sea ( Site 17940 and Ocean Drilling Program (ODP) Site 1144) differs by up to > 2 parts per thousand during the last glacial period. Given their close proximity, both core sites are located in the same biogeographic zone and nutrient regime, and it is thus unlikely that this offset is due to a true gradient in surface ocean conditions. In an attempt to resolve this offset, we have investigated the possible effects of two sedimentological parameters that can affect bulk sedimentary delta(15)N, namely, the variable contribution of inorganic N to bulk N in the sediment and the grain-size dependence of bulk delta(15)N. We find that... |
| Tipo: Text |
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| Ano: 2005 |
URL: https://archimer.ifremer.fr/doc/00230/34076/32639.pdf |
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| Chang, Yp; Chang, Cc; Wang, Lw; Chen, Mt; Wang, Ch; Yu, Ef. |
| A high-resolution (similar to 4 - 5cm/kyr) giant piston core record (MD962085) retrieved during an IMAGES II - NAUSICAA cruise from the continental slope of the southeast Atlantic Ocean reveal striking variations in planktonic foraminifer faunal abundances and sea-surface temperatures (SST) during the past 400,000 years. The location and high-quality sedimentary record of the core provide a good opportunity to assess changes in the intensity and position of the Benguela Current System and the Subtropical Convergence, two key features of the ocean-climate system in the south Atlantic. This record can be also used to evaluate the possible influence of Agulhas Current from the throughflow of the Indian Ocean into the South Atlantic. The planktonic foraminifer... |
| Tipo: Text |
Palavras-chave: Paleoceanography; Late Quaternary; Micropaleontology; South Atlantic. |
| Ano: 1999 |
URL: https://archimer.ifremer.fr/doc/00239/35070/34563.pdf |
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