Carbonate platform development responding to tectonic, oceanographic, and biotic transitions

要了解“全球变化”对当今世界的潜在影响，有必要了解环境变化本身的性质和速度；了解一个环境是否能够抵抗变化；以及了解变化是否可逆(即环境恢复)。现代地球系统只提供了环境的“时间快照”。缺失的是历史框架。地质记录(露头、采石场和钻探岩心)就是这样的档案，当与现代系统的数据结合在一起时，它为公众理解地球系统的潜在动态提供了唯一可靠的基础。对当地和全球外部环境压力非常敏感的两个地质背景是热带和温带碳酸盐陆架。碳酸盐沉淀物的产生(无论是通过无机或生物手段)对海水中微妙的物理和地球化学变化很敏感。这些现代大陆架上的海底沉积物通常被视为地球健康状况的“晴雨表”。这项拟议的研究将考察三个不同时代的古代碳酸盐陆架；以百万年为单位，~570年(乌拉圭)、~440年(安大略省)和~25年(新西兰)。它们都记录了不同的构造作用、古气候、海洋学和陆架发展过程中生物演化的框架，而且在两个案例中发生了变化。通过考察沉积历史和古生物记录所记录的环境变化，这项研究将有助于更好地理解这些类型的陆架如何应对相互竞争的环境压力、变化的速度，以及在抑制或加剧环境变化方面占主导地位的压力。这项工作将可用于帮助理解现代沉积体系。此外，其中两个平台(乌拉圭、安大略省)将提供有关地球系统如何应对与海洋学和生物转型有关的突出环境危机的信息。安大略省的平台还将提供关于沿着加拿大盾内的断层系统的长期(6亿年)构造作用的历史的信息。

To understand the potential impact of "global change" in today's world, it is necessary to appreciate the character and rate of environmental change itself; to understand if an environment can resist change; and, to understand if change is reversible (i.e., the environment recovers). Modern earth systems provide only a "temporal snapshot" of the environment. Missing is the historical framework. The geologic record (in outcrops, quarries, and drill cores) is such an archive, and, when incorporated with data from modern systems, provides the only sound basis for public understanding of the potential dynamics of the Earth system. Two geologic settings very sensitive to local and global external environmental pressures are tropical- and temperate-latitude carbonate shelves. Production of carbonate sediment (whether by inorganic or biological means) is sensitive to subtle physical and geochemical changes in the ocean water. Seafloor sediments along these modern shelves are often viewed to be the "barometers" of the Earth's health. The proposed research will examine three ancient carbonate shelves of different ages; in million years, ~570 (Uruguay), ~440 (Ontario) and ~25 (New Zealand). Each records different, and in two cases changing, frameworks of tectonism, paleoclimate, oceanography, and biotic evolution during shelf development. By examining environmental change as documented by the history of sedimentation and the paleontological record, the research will help better understand how these types of shelves can respond to competing environmental pressures, the rates of change, and what sets of pressures are dominant in suppressing or augmenting environmental change. The work will be transferable to help understand modern day depositional systems. In addition, two of the platforms (Uruguay, Ontario), will provide information about how the earth system responded to prominent environmental crisis associated with oceanographic and biotic transitions. The Ontario platform will also provide information about the history of long-lived (600 million year) tectonism along a fault system within the otherwise stable Canadian Shield.