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

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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.**