Determining main carbonate mineralogy, and the primary components of the non carbonate fraction, at four depths in core GC12, collected from the Capricorn Channel.

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.

在南澳大利亚大堡礁（Great Barrier Reef, GBR）的摩羯座海道（Capricorn Channel）内，于990.5米海平面以下深度（mbsl）处采集到一根重力岩芯（GC12）。对其他参数的分析表明，末次盛冰期（Last Glacial Maximum, LGM）位于岩芯内约175厘米深度处。采集了四个样品用于X射线衍射（X-ray Diffraction, XRD）分析：顶部两个样品（GC12-0，沉积物表面；GC12-30，30厘米深度）代表间冰期沉积物，下部两个样品（GC12-210，210厘米深度；GC12-330，330厘米深度）代表冰期沉积物。XRD分析显示，间冰期碳酸盐以方解石为主，主要来源于远洋碳酸盐生产；而冰期及过渡阶段则含有更多石英、长石、文石与镁方解石。这表明岩芯中远洋、陆源及礁平台物质的主导性随海平面变化而改变。