Environmental and tectonic controls on the evolution of Devonian reef complexes

现代珊瑚礁，如澳大利亚海岸外的大堡礁，是环境变化的敏感指标。在地球历史上的其他时期，类似的珊瑚礁也曾蓬勃发展，这些现已成为化石的珊瑚礁为古代海洋环境提供了宝贵的记录。珊瑚礁石灰岩和白云岩也具有经济价值，因为它们是矿藏和石油储藏库。加拿大西部和澳大利亚西北部保存完好的泥盆纪生物礁(3.8亿-3.6亿年)。这些泥盆纪生物礁记录了地球历史上一个关键时期，当时盘古大陆正在形成，全球温室和冰屋气候盛行，我研究的主要目的是通过对礁台序列的多学科研究，重建加拿大西部和澳大利亚西北部泥盆纪生物礁的演化史。这一目标将通过(1)详细研究台地沉积和沉积模式来实现；(2)利用化石和地球化学指标确定台地的沉积时代；(3)台地之间和台盆之间的沉积对比；(3)记录古土层和裸露生物礁中形成的岩溶；(4)研究富含有机质的岩石，这将提供有关营养水平的信息；以及(5)描述泥盆纪生物礁中记录的大规模灭绝事件的变化。我们将从加拿大西部和澳大利亚西北部选定的露头、采石场和钻芯中收集观测和岩石样本，并结合地球物理和显微镜数据以及化学分析。这种综合方法将使我们能够阐明海平面波动、地壳运动、沉积过程和沉积后蚀变之间的复杂相互作用，这些因素控制了泥盆纪生物礁的结构和演化。这项研究最终对理解生物礁的性质随着时间的推移具有重要的意义。用于预测现代珊瑚礁的行为，并评估人类活动对这些敏感生态系统的影响。

Modern coral reefs, such as the Great Barrier Reef off the Australian coast, are sensitive indicators of environmental change.  Similar reefs also flourished during other times in the Earth's past history, and these now fossilized reefs provide a valuable record of ancient marine environments.  Reef limestones and dolostones are also of economic interest as hosts for mineral deposits and as petroleum reservoirs.  Reefs of Devonian age (380-360 million years old) are well preserved in western Canada and northwestern Australia.  These Devonian reefs provide a record of a critical time in the Earth's history when the Pangea supercontinent was being assembled, global greenhouse and icehouse climates prevailed, and global extinction of marine organisms occurred.  The primary objective of my research is to reconstruct the history of Devonian reef evolution in western Canada and northwestern Australia by means of a multi-disciplinary study of the reef platform successions.  This objective will be achieved by (1) detailed examination of platform deposits and patterns of sedimentation; (2) determining the depositional ages of the platforms using fossil and geochemical indicators; (3) correlating deposits between platforms and from platform-to-basin; (3) documenting ancient soil horizons and karst formed in exposed reefs; (4) examining organic-rich rocks, which will provide information about nutrient levels; and (5) characterizing the changes across the mass extinction events recorded in the Devonian reefs.  Observations and rock samples will be collected from selected outcrops, quarries and drill-cores in western Canada and northwestern Australia, and integrated with geophysical and microscopy data and chemical analyses.  This integrated approach will allow us to elucidate the complex interplay of sea-level fluctuations, movements of the earth's crust, sedimentation processes and post-depositional alteration that have controlled the architecture and evolution of the Devonian reefs.  This research ultimately has important implications for understanding the nature of reefs through time, for predicting the behaviour of modern reefs and for assessing the impact of human activity on these sensitive ecosystems.