Th-230-normalized fluxes of biogenic components from the central and southernmost Chilean margin over the past 22,000 years

Fukuda, M; Harada, N; Sato, M; Lange, CB; Ahagon N.; KAWAKAMI H.; Miyashita W.; Pantoja S.; Matsumoto T.; Motoyama, I

Abstract

We report on Th-230-normalized fluxes of biogenic components-total organic carbon (TOC), total nitrogen (TN), calcium carbonate (CaCO3), and biogenic opal (Si-OPAL)-from two sediment cores collected at 36 degrees S off central Chile and covering the past 22 thousand years (kyr) (site PC-1), and at 52 degrees 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 Th-230-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 Th-230-normalized TOC flux was low during the last deglaciation until similar to 6 cal kyr BP, and then abruptly increased in the late Holocene. The Th-230-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 Th-230-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 Nino activity and biogenic component fluxes at the PC-1 site, even though at present El Nino events are negatively correlated with primary productivity in the upwelling area off Chile.

Más información

Título según WOS: Th-230-normalized fluxes of biogenic components from the central and southernmost Chilean margin over the past 22,000 years
Título de la Revista: GEOCHEMICAL JOURNAL
Volumen: 47
Número: 2
Editorial: GEOCHEMICAL SOC JAPAN
Fecha de publicación: 2013
Página de inicio: 119
Página final: 135
Idioma: English
Notas: ISI