Paläoumwelt- und Klimarekonstruktion in der Winterregenzone Südafrikas mit Hilfe integrierter Untersuchungen lakustriner und mariner Archive

• Antragsteller: Dr. Thomas Kasper
• Fachliche Zuordnung: Physische Geographie ; Mineralogie, Petrologie und Geochemie
• Förderung: Förderung von 2015 bis 2018
• Projektkennung: Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 282806576

• Erstellungsjahr: 2018

Zusammenfassung der Projektergebnisse

The presented project aimed to establish a high-resolution paleoenvironmental reconstruction form one of the scarce geoarchives in the Winter-Rainfall-Zone (WRZ) of South Africa, i.e., coastal lake Verlorenvlei. The record continuously covers the past 24 ka but reveals 14 event related deposits. These deposits are reflecting (i) the transgression of the ocean, (ii) marine storm-surge events (shell debris), or soil-erosion-events in the catchment. The transgression of the ocean starts at ca. 9.4 ka cal BP, which pins an absolute sea level marker of 13.9 m below the recent sea level for this time. Verlorenvlei has been under marine influence since this time, however, with some notable variations. Climatic variability is derived from a multi-proxy dataset incl. (in)organic geochemical, sedimentological, micropaleontological and leaf-wax isotope-geochemical analyses. The Last Glacial Maximum has been rather dry whereas during the Late Glacial (Termination 1) slightly moister but probably cool condition prevailed at the Verlorenvlei site. After 14.5 ka BP, renewed aridity at the west coast might reflect the Antanctic cold reversal (ACR). The Early Holocene is assumed to have been still dry, but shows first pulses of slightly enhanced bio-productivity. Between 7.2 and 4.1 ka cal BP distinctively moister climatic conditions with a potential year-round rainfall distribution indicate an influence of summer rainfall in the WRZ. This implies a shift of the limits or the extensions of the rainfall-zones. Thereafter, a shift back to drier conditions might also reflect a shift of the rainfall-zones back to the initial stage. The shifts in the rainfall patterns might well be associated with changes in the strength of seasonality. However, this is assumed to be driven by the strength and latitudinal position of the Southern Hemisphere Westerlies. The most recent part of the record shows a massive human impact with enhanced input of fertilizers, soil erosion and an associated eutrophication of the lake. The marine influence on Verlorenvlei during the covered period is in line with both, local records and regional sea level curves. The climatic variability derived from Verlorenvlei shows an in-phase pattern to records from the Year-Round-Rainfall-Zone but an antiphase pattern to records from the Summer-Rainfall-Zone. The overall driving force of climatic change is assumed to be the seasonal insolation difference between summer (DJF) and winter (JJA) rather than the mean annual insolation at the latitude of the Verlorenvlei location.

Projektbezogene Publikationen (Auswahl)

• (2016): Anthropogenic impact on the Swartvlei lake system in the Wilderness area (South Africa) as reflected in a sediment core. European Geosciences Union General Assembly 2016. 17-22 April 2016, Vienna, Austria
  Haberzettl, T., K. Kirsten, S. Franz, B. Reinwarth, J. Baade, G. Daut, T. Kasper, M. Meadows, Y. Su & R. Mäusbacher
  
• (2016): Environmental change at the southern Cape coast of South Africa as inferred from a high-resolution Holocene sediment record from Eilandvlei. European Geosciences Union General Assembly 2016. 17-22 April 2016, Vienna, Austria
  Wündsch, M., T. Haberzettl, M. Meadows, K. Kirsten, S. Meschner, P. Frenzel, J. Baade, G. Daut, R. Mäusbacher, T. Kasper, L. Quick, H. Cawthra & M. Zabel
  
• (2016): Paleoenvironmental reconstructions utilizing marine influenced sedimentary archives –The example of the coastal lake Verlorenvlei in the Winter Rainfall Zone of South Africa. 2016 AGU Fall Meeting.12-16 December 2016, San Francisco, USA
  Kasper, T., T. Haberzettl, M. Wündsch, P. Frenzel, M. Zabel, K. Kirsten, A. Carr, G. Daut, H. Cawthra, M. Meadows, L. Quick & R. Mäusbacher
  
• (2016): The potential of coastal lakes in the Winter-Rainfall-Zone of South Africa for paleoenvironmental reconstructions – an example from Verlorenvlei. European Geosciences Union General Assembly 2016. 17-22 April 2016, Vienna, Austria
  Kasper, T., T. Haberzettl, M. Lederer, M. Wündsch, P. Frenzel, M. Zabel, K. Kirsten, A. Carr, G. Daut, H. Cawthra, J. Baade, M. Meadows, L.Quick & R. Mäusbacher
  
• (2016): Using Inclination and Declination Data from South African Lake Sediment Records to Evaluate Radiocarbon-based Chronologies of the Past Millennium. 2016 AGU Fall Meeting. 12-16 December 2016, San Francisco, USA
  Haberzettl, T., M. Wündsch, T. Kasper, M. Meadows, J. Stoner, Y. Su & R. Mäusbacher
  
• (2017): Holocene paleoenvironmental change and sea level variations in South Africa. PAGES 5thOpen Science Meeting. 9-13 May 2017, Zaragoza, Spain
  Haberzettl, T., M. Wündsch, T. Kasper, R. Mäusbacher, H. Cawthra, G. Daut, P. Frenzel, K. Kirsten, L. Quick, M. Zabel, M. Meadows & RAiN-science team
  
• (2017): Holocene paleoenvironmental change in the Winter Rainfall Zone of SouthAfrica derived from sediments of coastal lake Verlorenvlei. GeoBremen 2017, 24-29 September 2017. Bremen, Germany
  Kasper, T., T. Haberzettl, E. Schefuß, M. Zabel, M. Wündsch, P. Frenzel , K. Kirsten, A. Carr, G. St- Onge, G. Daut, M. Meadows, L. Quick & R. Mäusbacher
  
• (2017): Paleoenvironmental changes during the Holocene in the Winter-Rainfall- Zone of South Africa – A continuous, high-, multi-proxy record from coastal lake Verlorenvlei. PAGES 5th Open Science Meeting. 9-13 May 2017, Zaragoza, Spain
  Kasper, T., T. Haberzettl, M. Wündsch, P. Frenzel, M. Zabel, K. Kirsten, A. Carr, G. St-Onge, G. Daut, M. Meadows, L. Quick & R. Mäusbacher