Surficial geology, stratigraphy, and placer deposits of the Ruby Range, Yukon Territory

The Quaternary history of the central Ruby Range, southwest Yukon, was studied through 1:50,000 scale surficial mapping and stratigraphic analysis. Stratigraphy in Gladstone Creek provides evidence for at least two glaciations of the Cordilleran Ice Sheet’s (CIS) St. Elias lobe, during marine oxygen isotope stages 2 and 4. Significant ice was produced from cirques and ice caps within the Ruby Range that likely contributed to the CIS incursion within Gladstone Creek. Advances from Ruby Range cirques appear to have preceded CIS advances and are preferentially preserved in stratigraphy due to lower base-levels associated with their advance. Stratigraphic units are constrained by tephrochronology, luminescence, and radiocarbon dating. 10Be dating on erratics suggests alpine glacier readvances occurred in Raft and Rockslide creeks at 13.7 ± 0.9 ka, significantly later than the last glacial maximum of the CIS. Placer deposits in Gladstone Creek have been reworked by repeated cycles of glaciation resulting in complex stratigraphic distributions, generally occurring on bedrock and false bedrock surfaces. Gold appears to be sourced from both epithermal mineralization in Kluane schist, as well as gold-rich porphyry mineralization in the Ruby Range batholith.