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International Journal of Earth Sciences

, Volume 99, Issue 2, pp 459–471 | Cite as

The middle to late Miocene climatic development of Southwest Africa derived from the sedimentological record of ODP Site 1085A

  • Bastian RotersEmail author
  • Rüdiger Henrich
Original Paper

Abstract

Sediments from the ODP Site 1085A were studied to investigate the impacts of global cooling in the Middle and Late Miocene on the climate in Southwestern Africa. The size composition of the sediment was analysed emphasising the silt fraction. A comparison with the modern grain size distribution and suitable transport processes made it possible to assign specific transport processes to the grain size composition. Three processes are considered for transport of terrigeneous silt: while there was no evidence found for (1) transport by ocean currents, the analyses showed signals of (2) wind transport indicating dry conditions associated with a cool climate and (3) fluvial transport that points to humid and warm conditions. Three climatic phases were defined. The first phase from 13.8 to 11.8 Myr reveals a stable humid climate in Southwest Africa independent of the Antarctic glaciations. During the second phase from 11.8 to 10.4 Myr the regional climate cooled considerably but was not drier. Additionally, the climate during this phase reacted to the Antarctic glaciations. This cooling-trend continued during phase 3 from 10.4 to 9.0 Myr with a significant increase in dust input, pointing to overall drier conditions. However, fluvial transport still remained as the main source.

Keywords

South West Africa Middle and late Miocene Climate cooling Aridification Grain size analysis 

Notes

Acknowledgments

We are thankful for various comments from the colleagues in the SedPal working group. David Heslop is thanked for additional comments and proofreading. Critical reviews by Dan Bosence and an anonymus reviewer improved the quality of this paper. Helga Heilmann and Brit Kockisch are thanked for laboratory assistance. Dorothee Koch is thanked for work on sample preparation. This research used samples and/or data provided by the International Ocean Drilling Program (IODP). This study was funded through the DFG Research Center/Excellence Cluster “The Ocean in the Earth System”.

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Copyright information

© Springer-Verlag 2008

Authors and Affiliations

  1. 1.MARUM, Center for Marine Environmental SciencesUniversity of BremenBremenGermany
  2. 2.Fronterra Geosciences GmbHViennaAustria
  3. 3.Department of GeosciencesUniversity of BremenBremenGermany

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