Holocene evolutionary history and accumulation rates for the granite based Lizard Island Fringing Reef System, Northern Great Barrier Reef

Lizard Island is located in the Northern Great Barrier Reef province, approximately 270km north of Cairns. Reef drilling was undertaken to investigate the Holocene evolution of the fringing reefs of Lizard Island. Radiocarbon dating of the cored coral material was then used to establish the chronology of the reef and to quantify the rate of development. \n\nThree drill cores were extracted, all from the windward margin because the leeward margin was too deep to access and did not form a conventional reef flat margin. The maximum depth reached was 4.5 m in core L1, with cores L2 and L3 being abandoned after encountering thick sand layers. \n\nThe cores were logged and photographed, and thin sections were made and petrographically examined. Corals that were determined to be in situ (by the orientation of their corallites) and free from internal cement and detritus by microscope examination were selected for radiocarbon dating.\n\nRadiocarbon dates indicate that the fringing reef at Lizard Island started growing directly on an assumed granite basement approximately 6.7 cal kyr BP at approximately 4.5 m below the reef flat surface. The windward margin at Lizard Island approached modern day sea level approximately 4 cal kyr BP. Rates of vertical accretion ranged from 0.5 to 0.7 m/kyr at Lizard Island.

蜥蜴岛（Lizard Island）位于大堡礁北部海域，距凯恩斯（Cairns）以北约270公里。本研究通过开展珊瑚礁钻探工作，探究蜥蜴岛岸礁（fringing reefs）的全新世演化过程。随后对岩芯中的珊瑚样品进行放射性碳定年法（Radiocarbon dating）分析，以此构建该礁体的年代序列并量化其发育速率。

本次共提取3个钻探岩芯，所有岩芯均取自迎风岸边缘——因背风岸边缘水深过深无法开展钻探，且未形成常规礁坪边缘。L1号岩芯的最大钻进深度达4.5米，L2与L3号岩芯因遭遇厚砂层而终止钻进。

对所有岩芯进行编录与拍照，并制备岩石薄片开展岩相学分析。经显微镜观测，选取那些依据珊瑚萼（corallites）排列方向判定为原位（in situ）生长、且无内部胶结物与碎屑的珊瑚样品用于放射性碳定年。

放射性碳测年结果显示，蜥蜴岛岸礁约于6.7校准千年BP（cal kyr BP）开始在推测的花岗岩基底上直接发育，发育位置位于礁坪表面以下约4.5米处。蜥蜴岛的迎风岸边缘约于4校准千年BP（cal kyr BP）达到现代海平面高度。该区域的垂直加积速率介于0.5至0.7米/千年之间。