Orbitally forced climate changes in the Tasman sector during the Middle Eocene

Jeroen Warnaar, Peter K. Bijl, Matthew Huber, Lisa Sloan, Henk Brinkhuis, Ursula Röhl, Ryan Sriver, Henk Visscher

Research output: Contribution to journalArticlepeer-review


The influence of orbital precession on early Paleogene climate and ocean circulation patterns in the southeast Pacific region is investigated by combining environmental analyses of cyclic Middle Eocene sediments and palynomorph records recovered from ODP Hole 1172A on the East Tasman Plateau with climate model simulations. Integration of results indicates that in the marine realm, direct effects of precessional forcing are not pronounced, although increased precipitation/runoff could have enhanced dinoflagellate cyst production. On the southeast Australian continent, the most pronounced effects of precessional forcing were fluctuations in summer precipitation and temperature on the Antarctic Margin. These fluctuations resulted in vegetational changes, most notably in the distribution of Nothofagus (subgenus Brassospora). The climate model results suggest significant fluctuations in sea ice in the Ross Sea, notably during Austral summers. This is consistent with the influx of Antarctic heterotrophic dinoflagellates in the early part of the studied record. The data demonstrate a strong precessionally driven climate variability and thus support the concept that precessional forcing could have played a role in early Antarctic glaciation via changes in runoff and/or precipitation.

Original languageEnglish (US)
Pages (from-to)361-370
Number of pages10
JournalPalaeogeography, Palaeoclimatology, Palaeoecology
Issue number3-4
StatePublished - Sep 15 2009
Externally publishedYes


  • General circulation model
  • Middle Eocene
  • Model-data comparison
  • Orbital forcing
  • Organic-walled dinoflagellate cysts
  • Southern Ocean

ASJC Scopus subject areas

  • Oceanography
  • Ecology, Evolution, Behavior and Systematics
  • Earth-Surface Processes
  • Palaeontology


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