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Title :^<230>Th-normalized fluxes of biogenic components from the central and southernmost Chilean margin over the past 22,000 years
Authors :Fukuda, Miho
Harada, Naomi
Sato, Miyako
Lange, Carina B.
Ahagon, Naokazu
Kawakami, Hajime
Miyashita, Wataru
Pantoja, Silvio
Matsumoto, Takeshi
Motoyama, Isao
Issue Date :20-Apr-2013
Abstract :We report on ^<230>Th-normalized fluxes of biogenic components—total organic carbon (TOC), total nitrogen (TN), calcium carbonate (CaCO_3), and biogenic opal (Si_<OPAL>)—from two sediment cores collected at 36°S off central Chile and covering the past 22 thousand years (kyr) (site PC-1), and at 52°S near the Pacific entrance of the Strait of Magellan and encompassing the past 13 kyr (site PC-3). During 13-8 calendar kyr before present (cal kyr BP), the ^<230>Th-normalized TOC flux at the PC-1 site was relatively high, pointing to increased productivity, whereas a marked decrease in the flux characterized the periods around 22-14 and 8-5 cal kyr BP. In contrast, at the PC-3 site, the ^<230>Th-normalized TOC flux was low during the last deglaciation until ~6 cal kyr BP, and then abruptly increased in the late Holocene. The ^<230>Th-normalized fluxes suggest that, compared to other periods, the biological pump functioned less effectively during 22-14 cal kyr BP and the middle Holocene off central Chile, and during 13-6 cal kyr BP off southernmost Patagonia. The changes from glacial to interglacial in the ^<230>Th-normalized biogenic components, which were controlled by changes in upwelling intensity at the PC-1 site and by the inflow of nutrients from the Pacific at the PC-3 site, can be explained by changes in wind direction and intensity associated with the latitudinal displacement of the southern westerly belt. In contrast, we found no obvious relationship during the deglacial and Holocene periods between El Niño activity and biogenic component fluxes at the PC-1 site, even though at present El Niño events are negatively correlated with primary productivity in the upwelling area off Chile.
URL :https://doi.org/10.2343/geochemj.2.0230
Type Local :雑誌掲載論文
ISSN :1880-5973
0016-7002
Publisher :The Geochemical Society of Japan
URI :http://hdl.handle.net/20.500.12000/46279
Citation :GEOCHEMICAL JOURNAL Vol.47 no.2 p.119 -135
Appears in Collections:Peer-reviewed Journal Articles (Faculty of Science)

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