Deciphering the Controls on Deep-Water Sediment-Routing Systems, Upper Nanaimo Group, BC: Integration of Geochronology and Stratigraphy
Date
2020-09-16
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Abstract
Convergent margins represent the intersection of multiple geodynamic systems (e.g., subduction, terrane accretion, magmatism). Sediment sinks (e.g., forearc basins) along convergent margins store evidence of these processes through their deposits’ compositions and spatial-temporal distributions. However, these records are often difficult to decipher as they are fragmented or deformed, particularly in the case of ancient systems. This thesis is focused on the evolution of convergent margins, with an emphasis on sediment routing systems that link tectonic hinterlands to sedimentary basins. Initial results from the thesis considered a numerical model to assess the geologic and analytical impacts on the accuracy of maximum depositional ages (MDAs) calculated from U-Pb detrital zircon. Modeling results informed construction of a chronostratigraphic framework for the Late Cretaceous Nanaimo Basin, which leverages extensive U-Pb detrital zircon and sandstone provenance datasets from an outcrop transect 160 km long by 2-3 km thick. The integration of field mapping and provenance information is used to demonstrate the evolution of multiple along-strike deep-water sediment routing systems in the upper Nanaimo Group, linking them to the tectonic evolution of the North American Cordillera. In the context of this stratigraphic framework, a depositional system model for confined deep-water channel units is developed. Channel-system deposits cluster spatially into three long-lived sediment fairways, each with a unique depositional history. Deepening of the Nanaimo Basin, the timing of basin-wide sedimentation events, structural deformation of the southernmost forearc basin, and changes in sediment provenance through the basin fill are correlated to either the formation of the subducting Kula Plate or later changes in its subduction vector. The research provides a multi-scale perspective into the evolution of a forearc basin over 20 M.y., shedding light on the evolution of the westernmost North American Cordillera during the Late Cretaceous.
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Detrital zircon, Nanaimo basin, Slope channel
Citation
Coutts, D. S. (2020). Deciphering the Controls on Deep-Water Sediment-Routing Systems, Upper Nanaimo Group, BC: Integration of Geochronology and Stratigraphy (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.