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Justin V. Strauss
The northern margin of North America records a protracted history of Neoproterozoic–early Paleozoic rifting and passive margin development, followed by the middle Paleozoic accretion of continental fragments. Contrasting tectonic models have been proposed for the history of continent separation, the role of strike-slip displacement during terrane accretion, and the Mesozoic opening of the Arctic Ocean. Here, I explore several of these models by investigating Neoproterozoic–early Paleozoic sedimentary and volcanic rocks across the northern margin of North American, as well as the main faulted boundaries between displaced terranes and autochthonous rocks of North America. First, I present a new tectonic model for late Ediacaran to early Cambrian rifting recorded in volcanic and sedimentary rocks of the Yelverton Formation exposed on northern Ellesmere Island, Canada. I constrain the timing of volcanism to ~570-530 Ma and relate it to decompression melting during progressive rifting. I suggest that rifting led to the separation of the North Slope subterrane of Arctic Alaska from the Laurentian margin. Second, I reconstruct the complex stratigraphy within the Porcupine Fault System, which marks the current tectonic boundary between the North Slope subterrane and the autochthonous Yukon block. I define a new succession of late Tonian sedimentary deposits, named the Ch’oodeenjìk succession. I suggest it represents a unique peri-Laurentian crustal fragment displaced along the Porcupine Fault System. Finally, I integrate detailed geological mapping with various thermochronometric and geochronometric techniques to determine the displacement history within the Porcupine Fault System. A new ca. 119 Ma U/Pb date on a calcite vein within the fault system highlights an episode of Early Cretaceous deformation, supporting models that involve terrane translation rather than rotation during the formation of the Canada Basin of the Arctic Ocean. Together, I propose that the northern margin of North America was characterized by Neoproterozoic-early Paleozoic separation of peri-Laurentian terranes subsequently displaced along a margin-parallel system of strike-slip faults, such as the Porcupine Fault System. This fault system was reactivated during the Cretaceous opening of the Canada Basin, eventually facilitating the translation of the Arctic Alaska terrane to its current position within the North American Cordillera.
Faehnrich, Karol, "Tectonic Evolution of the Northern Margin of North America" (2023). Dartmouth College Ph.D Dissertations. 154.
Available for download on Saturday, March 29, 2025