A gravity core (GC09) was collected from a depth of 166m within the Capricorn Channel, southern Great Barrier Reef (GBR). The percentage of calcium carbonate in samples collected from different depths was analysed, along with other parameters, to determine changes in carbonate mineralogy and terrestrial influx. The lowest percentage of calcium carbonate was recorded at ~60cm depth corresponding to the Last Glacial Maximum (LGM). The increase in the percentage of silt and mud during the LGM relates to a reduction in bioclastic carbonate production.