Great barrier reef environmental changes
Résumé
Integrated Ocean Drilling Program (IODP) Expedition 325, designed to investigate the fossil reefs on the shelf edge of the Great Barrier Reef, was the fourth expedition to utilize a mission-specific platform and was conducted by the European Consortium for Ocean Research Drilling (ECORD) Science Operator (ESO). The objectives of Expedition 325 were to establish the course of sea level change, define sea-surface temperature variations, and analyze the impact of these environmental changes on reef growth and geometry for the region over the period of 20-10 ka. To meet these objectives, a succession of fossil reef structures preserved on the shelf edge seaward of the modern barrier reef were cored from a dynamically positioned vessel in February-April 2010. A total of 34 boreholes across 17 sites were cored in depths ranging from 42.27 to 167.14 meters below sea level (lowest astronomical tide taken from corrected EM300 multibeam bathymetry data). Borehole logging operations in four boreholes provided continuous geophysical information about the drilled strata. The cores were described during the Onshore Science Party (OSP) at the IODP Bremen Core Repository (Germany) in July 2010, where minimum and some standard measurements were made. Preliminary postcruise dating of core catcher samples and initial observations of the cores made during the OSP confirm that coral reef material ranging in age from >30,000 to 9,000 calendar years before present (years before 1950 AD) was recovered during Expedition 325. Further postcruise research on samples taken during the OSP is expected to fulfill the objectives of the expedition.