Rock exhumation in the northern North American Cordillera

Thermochronological investigations into the timing, rates and amount of rock exhumation in the Northern Cordillera have focused on the high mountainous regions of Alaska, while much less is known about the Canadian parts of the orogen. The most recent (Miocene-Pliocene) and very rapid rock exhumation occurred in the Chugach-St. Elias Mountains in coastal southern Alaska and in the Alaska Range along the central Denali Fault. Rock exhumation in these areas is driven by the ongoing collision of the Yakutat microplate with the North American margin and flat-slab subduction underneath southern Alaska. Further from the plate boundary, the orogen is characterized by a series of thrust belts. Extensive study of the east-west trending thrust belt that composes the northern Brooks Range in northern Alaska reveals exhumation occurred in the Paleocene to Oligocene time. To the east the thrust belt bends southward into the Yukon and Northwest Territories where the Richardson and Mackenzie mountains form the eastern margin of the Cordillera. The sedimentary rocks of these thrust belt have been studied to evaluate their hydrocarbon potential. In general, these data reveal that exhumation occurred during the Late Cretaceous to early Eocene Cordilleran orogeny and was followed by multiple phases of limited (<1-2 km) exhumation in the late Eocene, Oligocene and early Miocene. The driver for these post-Cordilleran deformation phases is less clear and various models have been proposed.

Few thermochronological studies have been conducted in the interior of the Northern Canadian Cordillera. The sparse data document Paleocene-Eocene exhumation in the northern portion of the Yukon Tanana terrane. Overall, there is general lack of information to constrain the spatial pattern and timing of rock exhumation phases between the Denali Fault and the eastern deformation front. Filling these data gaps is needed to link the plate boundary processes in the west with the deformation at the eastern margin of the Cordillera and evaluate models for what is driving deformation and rock exhumation.