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

目前关于碳酸盐台地系统的认识主要是来自构造相对稳定的地质环境的现代和古代例子，例如沿大陆后缘、在远离汇聚边缘的前陆盆地内部、以及在板块内部的海洋平台上。这项拟议的研究将调查碳酸盐台地的沉积稳定性、地层几何学和成岩作用，以响应当地和区域构造作用。有两个地质区可以研究距离汇聚(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(&lt；1公里)结晶基底内的区域断裂系统(200公里长)之上。已证实了与远端(~1000公里)俯冲同步的局部断裂激活和沉积响应，但进一步的研究将确定该地台的区域结构、受构造影响的海平面变化的作用以及相应的碳酸盐产物及其蚀变的响应。这一历史将与纽芬兰西部板块边界变形前锋附近的当代地台和古代断裂系统轴线以外但在板块边界远端的当代地台进行比较。这样的比较可以提取出对海平面和平台开发的构造控制。(2)在智利中部，侏罗纪至早白垩世(1.4亿~9000万年)的碳酸盐台地发育在一个狭长的(约1000公里)盆地中，该盆地平行于碰撞板块边界并与之相邻，经历了伸展(加宽)。这是一个难得的机会，可以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。 研究成果将引起全球地质界的兴趣。这项研究将扩大目前对碳酸盐沉积体系构造敏感性的有限认识，并对比碰撞板块边界近端和远端的平台结构。这项研究将有助于描述从汇聚边界进入板块内部的沉积不稳定的潜在构造梯度，并解决继承结构重新激活对年轻沉积体系中地层模式的影响。将通过地质学会议和同行评议的期刊(国家和国际)传播成果。这个位于安大略省的项目将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区。这种接近强调了潜在的断层重新激活是一种现代的，而不仅仅是古代的地质后果。

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.