Ground penetrating radar (GPR) profiles were collected along mid-channel and side-channel bars from the confluence of the Yukon and White rivers in the Yukon, to Eagle, Alaska, a distance of 270 km. These profiles, although preliminary, demonstrate little variation in the thickness of valley-fill gravel (depth to bedrock) over that distance. Surveys show little difference in gravel thickness between the largest sediment source (White River) and more distal downstream reaches. The average thickness is approximately 10 m, which is equivalent to the maximum scour depth of the river. GPR surveys across the Tintina Fault along the Yukon River indicate a similar depth of fill compared to the upstream and downstream reaches from the fault zone, suggesting no significant recent vertical movement. These observations, when combined with the uplift history of the region (rates of 50-70 mm/ka determined in the Klondike area), suggest the region is likely undergoing either very slow uplift or is stable. No differential uplift is detectable within the error limits and sampling density of the GPR valley-fill method used in this study.
