A significant cross-strike structural discontinuity, the Beaver River Structure, has been recognized near the boundary between the north-central part of the Mackenzie Fold Belt and its southern part, the Liard Plateau. The Beaver River Structure is the northeast continuation of the Beaver Fault toward the confluence of the South Nahanni and Liard rivers and into the Interior Platform. It is oriented sub-parallel with the Liard Line farther south. Cumulative Laramide-aged dextral movement of 10 to 20 kilometres is inferred to have occurred along the Beaver River Structure. Small dextral offsets occur along the Beaver Fault, a possible surface manifestation of the Beaver River Structure and large, dominantly north-south oriented Laramide-aged folds and faults, such as the Kotaneelee and Liard synclines and the Nahanni Thrust Fault appear to have been locally rotated in a manner consistent with dextral strike-slip of at least 10 to 20 kilometres. The absence of Permian and Triassic strata in the Mackenzie Fold Belt north of the Beaver River Structure may indicate that uplift and erosion occurred north of the Beaver River Structure during the Early Cretaceous Columbian Orogeny. It is likely that the Beaver River Structure is an ancient, possibly Precambrian, structure that has been reactivated several times throughout Phanerozoic time.
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The Beaver River structure: A cross-strike discontinuity of possible crustal dimensions in the southern Mackenzie Fold Belt, Yukon and Northwest territories, Canada