Quaternary geology of the Carmacks map area, Yukon Territory

Abstract

The Carmacks map area has been partly or extensively glaciated a minimum of four times during the past ca. 1.5 million years. The two oldest, named pre-Reid glaciations occurred prior to the last magnetic reversal (>0.78 Ma BP). The pre-Reid glaciations and subsequent Reid Glaciation were separated by at least two periods of interglacial climate. Interglacial climates were similar to those of today or radically warmer. The Wounded Moose paleosol developed early in this period. Auriferous placers were deposited in the Dawson Range. The glacial ice was less extensive during Reid Glaciation than during the pre-Reid glaciations. During the period between the Reid and McConnell glaciations, the climate warmed to one comparable to the present. The Diversion Creek paleosol developed during this mild interval. The glacial ice cover of the latest (McConnell) glaciation was less extensive than that of the Reid Glaciation. Following the end of the McConnell Glaciation, the Yukon River, and presumably other major streams, incised close to their contemporary levels by the early Holocene. Volcano Mountain erupted around the Pleistocene-Holocene boundary and may have been active during the mid-Holocene. Bedrock is characteristically competent in the study area with the exception of the Carmacks Group. The most significant occurrences of placer gold occur in the Dawson Range. They result from the weathering and transport of lode gold associated with intrusions of the felsic subvolcanic Mount Nansen Group. All existing placer operations either overlie or are topographically downslope from Mount Nansen Group intrusions.