Provenance of Late Cretaceous to Paleogene rocks of the Alberta Foreland Basin: Rethinking retro-arc drainage systems in the Canadian Cordillera
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AuthorSuper, Samantha Christine
Committee MemberMatthews, William
SubjectAlberta Foreland Basin
MetadataShow full item record
AbstractLate Cretaceous to Paleogene strata of the Alberta Foreland Basin preserve a record of sediment dispersal in the Canadian Cordillera during the Laramide Orogeny. The provenance of these strata has only been loosely constrained. Detrital zircon U-Pb geochronology is paired with Lu-Hf isotopic analysis to better constrain the evolution of sediment provenance and dispersal patterns of Western Canada during the Late Cretaceous to Paleogene. Sampled sandstones (N = 19 samples; n = 4096 dates, total) cluster into 4 provenance groups using statistical analysis. The detrital zircon populations of most samples are dominated to some degree by near-depositional Cordilleran magmatic-derived grains and contain zircon populations from Yukon-Tanana Terrane and Intermontane Superterrane rocks. The appearance of a mixed detrital zircon signature refines the onset of the ‘Rundle Pulse’ thrust event in the Foreland Fold and Thrust Belt. Isotopically juvenile zircon grains sourced from the Coast Mountains Batholith are found in Cretaceous to Paleogene wedge strata. The presence of a juvenile isotopic signature in the near-depositional component of zircon populations necessitates a cross-Cordilleran delivery pathway. Transport via airfall ash across the main Cordilleran drainage divide has been previously hypothesized. However, an abrupt change in sediment provenance across the sub-Paskapoo Formation unconformity (ca. 63 Ma) cannot be reconciled with the airfall ash transport mechanism. The results are better explained with a model that invokes fluvial sediment transport of juvenile zircon grains to the foreland directly via integrated cross-Cordilleran river systems. The model shifts the main Cordilleran drainage divide west into the Coast Mountains Batholith or Intermontane Superterrane until Paskapoo Formation deposition. We suggest that the sudden shift in detrital zircon signature observed at the sub-Paskapoo Formation unconformity is associated with river capture and re-routing of fluvial systems west of the fold and thrust belt. These findings have implications for the timing and magnitude of the large-scale tectonics of the North American Cordillera.
CitationSuper, S. C. (2021). Provenance of Late Cretaceous to Paleogene rocks of the Alberta Foreland Basin: Rethinking retro-arc drainage systems in the Canadian Cordillera (Unpublished master's thesis). University of Calgary, Calgary, AB.
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