Tracing hydrological millennial-scale cycles in the late Quaternary of the Cariaco Basin and the southern Gulf of Cádiz using coccoliths and dinoflagellate cysts

Climate fluctuations in tropical to subtropical regions are coupled to hydrological changes. The reconstruction of these hydrological changes during rapid late Quaternary climate oscillations is crucial for climate change study. The present study demonstrates that coccoliths and dinoflagellate cysts are very useful as paleoclimatological indicators for the elucidation or a better understanding of the late Quaternary regional and global palaeoclimate. This study also reveals new insights in coccolithophore and dinoflagellate palaeoecology. At the outset, two fundamental studies were undertaken to strengthen dinoflagellate cysts as a proxy for paleoecological studies. Since so-called ‘standard’ palynological processing methods are still very variable and inflict damage on organic-walled microfossils to a certain extent, the effect on the determination of dinoflagellate cyst concentrations needed to be sorted out. Furthermore, since there were indications that process length variation of Lingulodinium machaerophorum is related to salinity, there was a need to assess its use for quantitative palaeosalinity reconstruction, which is of critical importance for better understanding of global climate change. Two locations were chosen for a high-resolution micropalaeontological study of hydrological millennial-scale cycles during Late Quaternary times: the Cariaco Basin, an anoxic basin offshore Venezuela and the Southern Gulf of Cádiz, offshore Morocco. Because of the high sedimentation rates, both sites contain a relatively undisturbed Late Quaternary climate record. Both record rapid, large climatic oscillations related to major hydrological changes caused by respectively the intertropical convergence zone (ITCZ) and the North Atlantic Oscillation (NAO). Results of the micropalaeontological analysis indicate that the changes in the dominance of river influx or upwelling cause important variations in plankton productivity in both locations. These variations are reflected in both assemblage changes and absolute abundance variation. Apart from the productivity reconstruction, changes in assemblage or morphology reflect changes in temperature and salinity. The seasonal and multi-year changes between upwelling and river dominated ecosystems, related in both regions to climatological shifts of respectively the ITCZ and NAO, can be extended to millennial-scale cycles and results in specific productivities, temperatures and salinities. Since millennial-scale shifts of both phenomena occur during the same periods (e.g. Younger Dryas), future work should elucidate the precise timing of both phenomena by comparing detailed multi-proxy records from north-south transects.

Grantor dc:publisher

Universiteit Gent

Year dc:date

2009

Author dc:creator

• Mertens, Kenneth

Contributors dc:contributor

• Louwye, Stephen

• Earth and Environmental Sciences
• dinoflagellate cysts
• millennial-scale
• Cariaco Basin
• Gulf of Cádiz
• North Atlantic Oscillation
• Intertropical Convergence Zone
• hydrological cycles
• late Quaternary
• coccoliths
• Lingulodinium machaerophorum

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

eng

Identifier

https://biblio.ugent.be/publication/592743
https://biblio.ugent.be/publication/592743/file/4334946

OAI identifier oai:identifier

oai:archive.ugent.be:592743