Tectonic signatures in carbonate platform sequences and diagenesis proximal and distal to convergent margins

碳酸盐台地层序的构造特征以及汇聚边缘近端和远端的成岩作用

• 批准号: RGPIN-2016-06170
• 负责人: Dix, George
• 金额: $ 1.75万
• 依托单位: Carleton University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2016
• 资助国家: 加拿大
• 起止时间: 2016-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=616139
• 关键词: Tectonic; signatures; carbonate; platform; sequences

The current state of knowledge about carbonate platform systems is dominated by modern and ancient examples from relatively tectonically stable geologic settings such as found along continental trailing margins; in the interior of foreland basins distant from convergent margins; and, on oceanic platforms within plate interiors. The proposed study will investigate the depositional stability, stratigraphic geometry, and diagenesis of carbonate platforms in response to local and regional tectonism. Two geologic regions allow study of tectonic signatures at different distances from convergent (subducting) plate boundaries. (1) In central Canada (SE Ontario), a Late Ordovician (450 million years) carbonate platform overlies a regional (200 km long) fault system within the underlying and shallowly buried (< 1 km) crystalline basement. Local fault reactivation and depositional response synchronous with distal (~1000 km) subduction has been demonstrated, but further study will define the regional architecture of the platform, the role of tectonically influenced sea-level change, and the corresponding response of carbonate production and its alteration. This history will be compared with a contemporary platform proximal to the plate-boundary deformation front in western Newfoundland and contemporary platforms beyond the axis of the ancient fault system but distal to the plate boundary. Such comparisons allow extraction of tectonic controls on sea level and platform development. (2) In central Chile, carbonate platforms of Jurassic to Early Cretaceous age (140 to 90 million years) developed in a narrow elongate (~1000 km) basin undergoing extension (widening) parallel to and adjacent to the collisional plate boundary. This is a rare opportunity to study platform architecture and diagenesis and the impact of tectonism on platforms immediately adjacent to a subduction zone. Research outcomes will be of interest to the global geological community. The research will expand on the current limited knowledge about tectonic sensitivity of carbonate depositional systems, and contrasting platform architecture in proximal to distal positions from collisional plate boundaries. The study will help characterize a potential tectonic gradient of depositional instability directed into the plate interior from convergent boundaries, and address the impact of reactivation of inherited structure on stratigraphic patterns in younger sedimentary systems. Dispersal of results will be through geological conferences and peer-reviewed journals (national, international). There will be community-level interest in the Ontario-based project because the ancient fault system underlies many rural and urban communities, and lies adjacent to the active Western Quebec Seismic Zone. Such proximity underscores potential fault reactivation as a modern, not just ancient, geological consequence.

目前关于碳酸盐台地系统的知识状况主要是来自相对构造稳定的地质环境（例如沿大陆尾缘发现的）的现代和古代实例；远离汇聚边缘的前陆盆地内部；并且，在板块内部的海洋平台上。拟议的研究将调查碳酸盐台地的沉积稳定性、地层几何形状和成岩作用对局部和区域构造运动的响应。两个地质区域允许研究距会聚（俯冲）板块边界不同距离的构造特征。 (1) 在加拿大中部（安大略省东南部），晚奥陶世（4.5 亿年）碳酸盐台地覆盖在下伏浅埋（< 1 公里）结晶基底内的区域性（200 公里长）断层系统之上。与远端（~1000公里）俯冲同步的局部断层再活动和沉积响应已经得到证实，但进一步的研究将确定该平台的区域结构、构造影响的海平面变化的作用，以及碳酸盐岩生产及其蚀变的相应响应。这段历史将与纽芬兰西部靠近板块边界变形前缘的当代台地以及位于古代断层系统轴之外但远离板块边界的当代台地进行比较。这种比较可以提取构造对海平面和平台开发的控制。 (2) 在智利中部，侏罗纪至早白垩世（140 至 9000 万年）的碳酸盐台地发育在一个狭窄的细长（约 1000 公里）盆地中，该盆地经历平行于并邻近碰撞板块边界的伸展（加宽）。这是研究平台结构和成岩作用以及构造作用对紧邻俯冲带的平台的影响的难得机会。 研究成果将引起全球地质界的兴趣。该研究将扩展目前关于碳酸盐沉积系统构造敏感性的有限知识，并对比碰撞板块边界近端和远端位置的平台结构。该研究将有助于表征从会聚边界引导到板块内部的沉积不稳定性的潜在构造梯度，并解决继承结构的重新激活对较年轻沉积系统中地层模式的影响。结果将通过地质会议和同行评审期刊（国家、国际）传播。安大略省的项目将会引起社区层面的兴趣，因为古老的断层系统位于许多农村和城市社区的下方，并且毗邻活跃的魁北克西部地震带。这种接近性强调了潜在的断层重新激活是一种现代地质后果，而不仅仅是古代地质后果。