Quantifying the isotopic composition of oxygen and carbon with increasing depth in core GC11, located in the Capricorn Channel

A gravity core (GC11) was collected from a depth of 502 mbsl within the Capricorn Channel, southern Great Barrier Reef (GBR). The data from stable isotopes of Globigerinoides ruber were analysed to allow a preliminary understanding of the hemipelagic sedimentary environment over the last glacial / interglacial cycle. The results suggest that the core reaches the Last Glacial Maximum (LGM) at ~30cm depth. From matching the 18O G. ruber curve with Martinson et al. (1987), 4 glacial cycles can be determined, incorporating Marine Isotope Stage (MIS) 1 through to MIS 11. Isotopically heavier 18O values at ~460cm, ~345cm, 150cm, and 30cm correspond respectively to MIS 10, MIS 8, MIS 6 and the LGM. The d13C shows a trough lagging behind the 18O high during the glacial, although there are considerable fluctuations between MIS 8 and 6.