Oligocene biogenic siliceous deposits on the slope of the northern South China Sea

Author(s): Wang Rujian; Fang Dianyong; Shao Lei; Chen Muhong; Xia Peifen; Qi Jingyu
Author Affiliation(s): Primary:
Tongji University, Shanghai, China
South China Sea Institute of Oceanology, China
Volume Title: Science in China. Series D, Earth Sciences
Source: Science in China. Series D, Earth Sciences, 44(10), p.912-918. Publisher: Science in China Press, Beijing, China. ISSN: 1006-9313
Note: In English. 21 refs.; illus., incl. 1 table
Summary: The abundance of radiolarian, diatom and sponge spicules and H4SiO4 in pore waters increases abruptly at the boundary between the Early and Late Oligocene (about 30-27.5 Ma) at Site 1148 in the northern South China Sea (SCS), indicating high biogenic silica accumulation during this time. At the same time (about 30-28 Ma), high biogenic silica deposition occurred in the central equatorial Pacific. A comparison of biogenic silica accumulation at Site 1148 in of the SCS with that at Site 929 in the Atlantic verifies that the biogenic silica accumulation between low latitude Pacific and Atlantic Oceans expresses the evident relationship of compensation during the Oligocene. Biogenic silica accumulation decreased in the Atlantic, whereas it increased in the Pacific at the boundary between the Early and Late Oligocene. It resulted from the formation and presence of North Atlantic Deep Water (NADW) in the Atlantic basin, indicating an intensive basin-basin fractionation. XRD analysis and SEM observation of the samples from Site 1148 demonstrate that most of the radiolarian, diatom and sponge spicules have suffered from dissolution and reprecipitation, suggested by the opal-A--opal-CT transformation. As a result of the transformation, porosity increased, but dry and bulk densities decreased, reflecting the consequences of diagenesis on the physical properties of sediments.
Year of Publication: 2001
Research Program: ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Algae; Atlantic Ocean; Biostratigraphy; Ceara Rise; Cenozoic; Continental slope; Deep-water environment; Diatoms; Equatorial Atlantic; Invertebrata; Leg 154; Leg 184; Microfossils; North Atlantic; North Atlantic Deep Water; North Pacific; Northwest Pacific; ODP Site 1148; ODP Site 929; Ocean Drilling Program; Oligocene; Pacific Ocean; Paleo-oceanography; Paleogene; Plantae; Porifera; Protista; Radiolaria; Siliceous composition; South China Sea; Spicules; Tertiary; West Pacific
Coordinates: N185010 N185010 E1163356 E1163356
Record ID: 2009023090
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