Southern-ocean and glaciogenic nutrients control diatom export production on the Chile margin
Biogenic particle flux was reconstructed using 230-Thorium normalization at two sites on the southern Chile margin. ODP Site 1233 at 41S, 838 m depth, is at the southern limit of the PeruChile upwelling system, where the northern extent of the Antarctic Circumpolar Current impinges on the South Amer...
| Published in: | Quaternary Science Reviews |
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| Main Authors: | , , , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
Pergamon-Elsevier Science Ltd
2014
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| Subjects: | |
| Online Access: | https://doi.org/10.1016/j.quascirev.2014.06.015 http://ecite.utas.edu.au/93245 |
| Summary: | Biogenic particle flux was reconstructed using 230-Thorium normalization at two sites on the southern Chile margin. ODP Site 1233 at 41S, 838 m depth, is at the southern limit of the PeruChile upwelling system, where the northern extent of the Antarctic Circumpolar Current impinges on the South American continental margin. ODP Site 1234, at 36S, 1014 m depth, is located within the core of the coastal upwelling system near the mouths of the Bio Bio and Itata Rivers. At 41S, opal, lithogenic and carbonate fluxes are greatest during the Last Glacial interval (2620 ka), carbonate has a secondary peak during the mid Holocene (∼8 ka) and organic carbon fluxes increase slightly from 17 ka to the present. At 36S, large lithogenic fluxes are observed both during the Last Glacial interval and the Holocene, and a maximum in organic carbon flux is observed during the late Holocene (∼5 ka) without an accompanying peak in opal flux. These reconstructed fluxes at 36S and 41S fit within a larger latitudinal pattern of a poleward increase in the magnitude of opal flux during the glacial period. The pattern of normalized opal flux, opal mass accumulation rate and opal:carbonate ratios is consistent with either i) enhanced supply of Si from the Southern Ocean, as proposed by the Silicic Acid Leakage Hypothesis or ii) enhanced Si and Fe delivery from land, driven by glacial erosion. The pattern of reconstructed export production supports our view that the appearance of more reducing conditions in the sediments upon deglaciation was most likely driven by decreased ventilation, rather than increased local productivity. |
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