A gravity core (GC12) was collected from a depth of 990.5 mbsl within the Capricorn Channel, southern Great Barrier Reef (GBR). Analysis of other parameters revealed the Last Glacial Maximum (LGM) sitting at a depth of ~175cm into the core. Four samples were collected for X-ray Diffraction (XRD) analysis; the top two, at the sediment surface (GC12-0) and at 30cm (GC12-30) represent interglacial sediment, while the lower two, at 210cm (GC12-210) and 330cm (GC12-330) represent glacial sediment. XRD analysis suggests that the majority of the carbonate is calcite during the interglacials, primarily from pelagic carbonate production. During the glacials and transitions more quartz, feldspar, aragonite and Mg calcite are present. This suggests that there is a changing dominance of pelagic, terrigenous and reef platform material within the core related to sea-level variations.