X-ray fluorescence measurements and bulk organic carbon analyses of ODP Hole 175-1075A

DOI

Records of organic matter accumulation, organic carbon isotopic composition and iron content covering the last 1.7 Ma are presented for the Congo Fan Ocean Drilling Program (ODP) Site 1075, and are compared with their counterparts from ODP Site 663 in the equatorial upwelling region. They are discussed with regard to variations in African precipitation and Congo River discharge and in the context of changes in trade-wind-driven marine productivity for the tropical Atlantic at periodicities typical of Milankovitch forcing. On the Congo Fan, elevated total organic carbon mass accumulation rates (TOC MAR) and Fe intensities occur predominantly during interglacial periods when the African monsoon was most intense. Band-pass filtering applied to TOC MAR shows distinct precessional variations, indicating that the African climate was largely controlled by low-latitude insolation changes. Only for the last 0.6 Ma, an interval of enhanced glacial-interglacial climate changes, is the precessional TOC MAR signal superimposed by a strong 100 ka oscillation. In contrast, variations in terrestrial iron input to the Congo Fan indicate pronounced 100 ka variance already well before global glacial-interglacial cycles increased in amplitude between 0.9 and 0.6 Ma. Obliquity cycles in the Fe signal are strongly expressed for the last 0.9 Ma. The highest amplitudes in the precessional variance of fluvial Fe input occur when amplitudes in the 100 ka oscillation were at intermediate levels and reveal a 800 ka cycle in phase shift with respect to precessional forcing. Together with a pronounced 800 ka signal in the 100 ka amplitude variations during the last 1.7 Ma, the Congo Fan iron record therefore suggests that eccentricity modulation of the low-latitude insolation directly influenced the equatorial African monsoon system and probably the weathering conditions on land. It further suggests that low-latitude precessional forcing and monsoonal response in the tropics might have played an important role for 100 ka cycles in global climate well before huge continental ice sheets existed.

Supplement to: Jahn, Britta; Schneider, Ralph R; Müller, Peter J; Donner, Barbara; Röhl, Ursula (2005): Response of tropical African and East Atlantic climates to orbital forcing over the last 1.7 Ma. In: Head, M J & Gibbard, P L (eds.) Early–Middle PleistoceneTransitions: The Land–Ocean Evidence. Geological Society, London, Special Publications, 247, 65-84

Identifier
DOI https://doi.org/10.1594/PANGAEA.779849
Related Identifier IsSupplementTo https://doi.org/10.1144/GSL.SP.2005.247.01.04
Related Identifier References https://nbn-resolving.org/urn:nbn:de:gbv:46-ep000103218
Metadata Access https://ws.pangaea.de/oai/provider?verb=GetRecord&metadataPrefix=datacite4&identifier=oai:pangaea.de:doi:10.1594/PANGAEA.779849
Provenance
Creator Jahn, Britta; Schneider, Ralph R ORCID logo; Müller, Peter J; Donner, Barbara; Röhl, Ursula ORCID logo
Publisher PANGAEA
Publication Year 2005
Rights Creative Commons Attribution 3.0 Unported; https://creativecommons.org/licenses/by/3.0/
OpenAccess true
Representation
Resource Type Supplementary Publication Series of Datasets; Collection
Format application/zip
Size 2 datasets
Discipline Earth System Research
Spatial Coverage (10.075 LON, -4.785 LAT); Benguela Current, South Atlantic Ocean
Temporal Coverage Begin 1997-08-23T19:50:00Z
Temporal Coverage End 1997-08-24T23:40:00Z