Jahn, B. et al. (2005): Response of tropical African and East Atlantic climates to orbital forcing over the last 1.7 Ma

Leg/Site/Hole:
ODP 108
ODP 111
ODP 175
ODP 175 1075
ODP 175 1077
ODP 108 663
ODP 111 677
Identifier:
2006-031595
georefid

Creator:
Jahn, B.
Universitaet Bremen, Fachbereich Geowissenschaften, Bremen, Federal Republic of Germany
author

Schneider, R. R.
Christian-Albrechts-Universitaet zu Kiel, Federal Republic of Germany
author

Mueller, P. J.
author

Donner, B.
author

Roehl, U.
author

Identification:
Response of tropical African and East Atlantic climates to orbital forcing over the last 1.7 Ma
2005
In: Head, Martin J. (editor), Gibbard, Philip L. (editor), Early-middle Pleistocene transitions; the land-ocean evidence
Geological Society of London, London, United Kingdom
247
65-84
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 compare 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 800ka 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.
English
Coverage:Geographic coordinates:
North:1.1209
West:-83.4414East: 10.2611
South:-5.1048

Quaternary geology; Isotope geochemistry; Africa; Atlantic Ocean; C-13/C-12; carbon; Cenozoic; chemostratigraphy; climate forcing; Congo Fan; cores; correlation; depositional environment; East Pacific; Equatorial Atlantic; Equatorial Pacific; glacial environment; interglacial environment; iron; isotope ratios; isotopes; Leg 108; Leg 111; Leg 175; lithofacies; magnetic properties; magnetic susceptibility; metals; O-18/O-16; Ocean Drilling Program; ODP Site 1075; ODP Site 1077; ODP Site 663; ODP Site 677; orbital forcing; organic compounds; oxygen; Pacific Ocean; paleoclimatology; paleoecology; paleoenvironment; paleomagnetism; productivity; Quaternary; South Atlantic; Southeast Atlantic; stable isotopes; statistical analysis; terrigenous materials; time series analysis; total organic carbon; tropical environment;

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