NW African climate variations during the last 47,000years: Evidence from organic-walled dinoflagellate cysts.

Holzwarth, Ulrike, Meggers, Helge, Esper, Oliver, Kuhlmann, Holger, Freudenthal, Tim, Hensen, Christian and Zonneveld, Karin A.F. (2010) NW African climate variations during the last 47,000years: Evidence from organic-walled dinoflagellate cysts. Palaeogeography Palaeoclimatology Palaeoecology, 291 (3-4). pp. 443-455. DOI 10.1016/j.palaeo.2010.03.013.

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NW African climate shows orbital and millennial-scale variations, which are tightly connected to changes in
marine productivity. We present an organic-walled dinoflagellate cyst (dinocyst) record from a sediment
core off Cape Yubi at about 27°N in the Canary Basin covering the time period from 47 to 3 ka before present
(BP). The dinocyst record reflects differences in upwelling intensity and seasonality as well as the influence
of fluvial input. Sea-level changes play an important role for the upwelling pattern and productivity signals at
the core site. Within the studied time interval, four main phases were distinguished. (1) From 45 to 24 ka BP,
when sea-level was mostly about 75 m lower than today, high relative abundances of cysts of heterotrophic
taxa point to enhanced upwelling activity, especially during Heinrich Events, while relatively low dinocyst
accumulation rates indicate that filament activity at the core location was strongly reduced. (2) At sea-level
lowstand during the LGM to H1, dinocyst accumulation rates suggest that local filament formation was even
more inhibited. (3) From the early Holocene to about 8 ka BP, extraordinary high accumulation rates of most
dinocyst species, especially of Lingulodinium machaerophorum, suggest that nutrient supply via fluvial input
increased and rising sea-level promoted filament formation. At the same time, the upwelling season
prolongated. (4) A relative increase in cysts of photoautotrophic taxa from about 8 ka BP onwards indicates
more stratified conditions while fluvial input decreased. Our study shows that productivity records can be
very sensitive to regional features. From the dinocyst data we infer that marine surface productivity off Cape
Yubi during glacial times was within the scale of modern times but extremely enhanced during deglaciation.

Document Type: Article
Keywords: Geochemistry; Northwest Africa; Dinoflagellate cysts; Fluvial input; Sea-level; Productivity; Upwelling
Research affiliation: MARUM
OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-MG Marine Geosystems
OceanRep > The Future Ocean - Cluster of Excellence
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1016/j.palaeo.2010.03.013
ISSN: 0031-0182
Projects: Future Ocean
Date Deposited: 26 Jul 2010 07:34
Last Modified: 05 Jul 2019 09:24
URI: http://oceanrep.geomar.de/id/eprint/8724

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