IODP Expedition 325 “Great Barrier Reef Environmental Changes” 

Fieldwork on the GBR Coral reefs offer the potential to reconstruct past climates. The close association of corals with sea level allow the elevation of fossil corals to be used as paleo markers for sea level. The chemistry of coral skeletons can also be used to infer past environmental conditions. The great barrier reef system off the NE coast of Australia has preserved fossil coral reefs that developed while sea level was lower than present. These fossil reefs form the structures on which the modern reefs have developed, but also have preserved within them records of sea level rise and past sea surface temperature.

In 2007 these fossil reefs were surveyed using multibeam sonar, seismic profiles, and surface sampling. Subsequently, in 2010, IODP Expedition 325 drilled into these drowned reef features to recover sequences of corals. The principle scientific objectives of the expedition are to: 

  • Webster et al. 2008 GBR multibeamTo establish the course ofpostglacial sea level rise at the Great Barrier Reef.
  • To define sea-surface temperature variations for the region over the period 20 to 10 ka.
  • To analyze the impact of sea level changes on reef growth and geometry.

Coral cores were recovered using a dynamically position drill ship, the Greatship Maya. This allowed the extraction of cores with minimal disturbance of the environment. Detailed core descriptions, measurements, and sampling were performed at the IODP core repository in Bremen. Oxford’s role in this project is to establish U-Th chronologies for the cores to place the SST and reef growth records in context and to allow the construction of past level records. 

A Giant Yonic Clam