34-3 Geomorphic Evidence of Active Tectonics in the Mackenzie Mountains, Canada

Session: Advancing Earthquake Geology and Surficial Deformation from Geologic Provinces to Political Entities through Multidisciplinary High-Resolution Data (Posters)

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Abstract:

Seismic records and GPS data reveal that the Mackenzie Mountains in Northwestern Canada are actively deforming despite being located nearly ~1000 km east of the active Pacific-Yakutat-North America plate boundary. To determine the mechanism(s) driving this deformation, and the role of pre-existing structures in accommodating it, it is first necessary to identify the spatial pattern of deformation and active faults. To do this, we used a suite of areal and catchment-scale geomorphometric indicators of active uplift. These metrics are sensitive to geomorphic processes that develop over 10²–10⁵ years and therefore link deformation documented by geophysical data (decades) with the more distant geologic past (10⁶ years). 

We searched the Mackenzie Mountains and Mackenzie Plain (~300,000 km²) for active faults which we identified using the coincidence of high areal hypsometry, knickpoint clusters, and topographic lineaments. We identify the Battlement fault, a ~100 km long west-dipping thrust fault, in the southern Mackenzie Mountains as an active fault. We confirm Quaternary activity along this structure using the morphologies of 41 catchments that drain the hanging wall of this fault. We quantified catchment morphology using hypsometry (index and curves), catchment volume-to-area ratio, valley floor width-to-height ratio, and surface roughness. We interpret along-strike trends in multiple indices to reflect three segments with different relative uplift rates. The surface trace of the Battlement fault is located ~25 km east of the epicenters of the two M > 6 Nahanni earthquakes in 1985. Focal mechanisms for these earthquakes indicate that rupture occurred along a ~N-S-striking thrust fault. It is probable that displacement during these events was accommodated along the Battlement fault. Our characterization of relative uplift rates along the Battlement fault suggests that this fault has been active since at least the Pleistocene.  

We only found evidence for one other potentially active fault in the study region: an enigmatic topographic lineament located ~200 km north of the Battlement fault with ~60 m of vertical separation that may also be an active fault. The general absence of geomorphic evidence for active faulting in the Mackenzie Mountains may indicate that active deformation is primarily accommodated along blind faults and folding. 

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-9372

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