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| Titel |
Anoxic sediments off Central Peru record interannual to multidecadal changes of climate and upwelling ecosystem during the last two centuries |
| VerfasserIn |
D. Gutiérrez, A. Sifeddine, J. L. Reyss, G. Vargas, F. Velazco, R. Salvatteci, V. Ferreira, L. Ortlieb, D. Field, T. Baumgartner, M. Boussafir, H. Boucher, J. Valdés, L. Marinovic, P. Soler, P. Tapia |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7340
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| Digitales Dokument |
URL |
| Erschienen |
In: 1st Alexander von Humboldt International Conference ; Nr. 6 (2006-01-09), S.119-125 |
| Datensatznummer |
250003247
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| Publikation (Nr.) |
 copernicus.org/adgeo-6-119-2006.pdf |
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| Zusammenfassung |
| High-resolution paleo-environmental and paleo-ecological archives in
laminated sequences are present in selected areas from the upper continental
Peruvian margin within the oxygen minimum zone. We present initial results
of a multidisciplinary study (the PALEOPECES project) that aims to
reconstruct environmental and ecosystem variability during the past 200
years from high-resolution records. We report chronology development,
sediment structure, elemental, organic, and mineralogical compositions of a
box core collected at 300 m depth off Pisco, central Peru. An average
sedimentation rate of 2.2 mm y-1 was estimated from downcore excess
210Pb activities for the last 100-150 years. Extending this rate
further downcore indicates that a slump located at 52 cm depth from the top
of the core can be correlated with a large tsunami that struck the coast of
central Peru in 1746. X-ray analyses reveal laminated structures composed of
couplets of light and dark laminae. Observations under polarized microscope
show that light laminae are dominated by more dense, detrital and
terrigenous material, while dark laminae are less dense with greater
concentrations of amorphous biogenic silica. Downcore variations in dry bulk
density and X-ray radioscopy of gray level show similar patterns, including
a major shift at 34 cm depth (ca. mid-nineteenth century). A finely laminated
sequence, which may include annual varves, is present between 34 cm depth
and the slump layer. Sediment characteristics of the sequence suggest
increased seasonality of terrigenous versus biogenous sedimentation during
the corresponding period. In addition to a mid-nineteenth century change and
considerable multidecadal variability in TOC, there is a positive trend in
the past 50 years. Mineralogical analyses from a Fourier Transformed
Infrared Spectroscopy (FTIR) of the upper core covering the last 25 years,
indicate higher concentrations of the mineral fraction (quartz, feldspar,
kaolinite and illite) in layers including large El Niño events (1982-1983,
1986-1987 and 1997-1998), with the largest peak during the 1997-1998 episode.
These results confirm that anoxic sediments off Pisco are suitable archives
to investigate interannual and decadal changes in oceanographic conditions
and climate of the northern Humboldt upwelling system. |
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