Universität zu Köln

Saupe, Anna ORCID: 0000-0002-6484-4857 (2023). Benthic Foraminifera as Proxies in Contourite Drift Systems. PhD thesis, Universität zu Köln.

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Abstract

Benthic foraminifera are highly adaptable to a wide range of environments, which makes them excellent tools for the reconstruction of palaeoenvironments. Certain species prefer regions with significantly increased current velocities, such as present in contourite drift systems (CDS). Contourites form elongated sedimentary bodies that are deposited under persistent, contour-parallel bottom currents and cover extensive areas of the Atlantic Ocean. An increased current activity substantially affects the composition of the associated epibenthic community, and some benthic foraminiferal species preferably settle on elevated substrates, summarised as elevated epifauna (EEF). EEF species optimise the acquisition of food particles carried by strong bottom currents, giving them a competitive advantage over other epibenthic microorganisms. The EEF was established at the Iberian Margin (Northeast Atlantic Basin) within the Mediterranean Outflow Water (MOW) and evaluated for its suitability as a bottom current indicator (Schönfeld, 1997). In this thesis, biogeographic distribution patterns of benthic foraminifera in sediment surface samples from CDSs beyond the Northeast Atlantic Basin, within the low and high latitudes of the Atlantic Ocean, are evaluated. Investigations along the Brazilian continental margin (Campos and Brazil basins, 11-22°S, 36-40°W) reveal a diverse foraminiferal community, although with a rather poor EEF, that is almost exclusively represented by Cibicidoides wuellerstorfi. Samples from the North Atlantic Iceland (Björn and Gardar Drift, 55-62°N, 23-28°W) and Irminger basins (Eirik Drift, 57-59°N, 45-49°W) also reveal lacking or sparse EEF occurrences. Instead, tubular agglutinated suspension feeders, such as Rhabdammina abyssorum or Saccorhiza ramosa, preferably colonise the weak to moderate current regime in the Björn and Gardar drifts. In the slightly enhanced currents of the Eirik Drift, abundances of EEF taxon Cibicidoides wuellerstorfi are recorded. The integration of the new data sets with previous studies, primarily from the Iberian Margin, reveal that temperature variations, substrate properties, hydrodynamic conditions at the sediment-water interface, and suspended organic matter crucially contribute to the assemblage composition in CDSs. The hydrodynamic properties of the warm (13°C) and saline (38.4) MOW, its strongly increased current velocities (up to 100 cm/s) and its Mediterranean origin create a unique environment that seems to be highly beneficial for EEF species. This contrasts with an environment that is largely controlled by the Atlantic Meridional Overturning Circulation (AMOC) comprising major cold (> 4°C) and comparatively less saline (34.2-34.9) deep water masses with weak to moderate bottom current intensities (max. 30 cm/s). In this oligotrophic deep-sea environment, agglutinated tubular suspension feeders may serve as indicators for the reconstruction of weaker bottom currents at the high latitudes. However, further studies will be necessary to understand a potential taphonomic bias on their abundance in the fossil record.

Item Type:	Thesis (PhD thesis)
Creators:	Creators Email ORCID ORCID Put Code Saupe, Anna anna.saupe@uni-koeln.de orcid.org/0000-0002-6484-4857 UNSPECIFIED
URN:	urn:nbn:de:hbz:38-700644
Date:	25 May 2023
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Geosciences > Institute of Geology and Mineralog
Subjects:	Earth sciences
Uncontrolled Keywords:	Keywords Language Benthic Foraminifera English Contourite Drift Systems English Atlantic Ocean English Bottom Currents English Elevated Epifauna English UNSPECIFIED English
Date of oral exam:	25 May 2023
Referee:	Name Academic Title Grunert, Patrick Prof. Dr. Schmiedl, Gerhard Prof. Dr.
Funders:	Deutsche Forschungsgemeinschaft, Project GR52851/1-1
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/70064