Analyses minéralogiques multivariées de sédiments du Wisconsinien supérieur au sud-ouest du Yukon

Abstract

For this study, 84 samples of glacial and juxtaglacial sediments were collected in valleys of the Ruby Range and Aishihik Basin (southwestern Yukon). Analyses were conducted to quantify the heavy minerals in the sand fraction and to assess the petrography of the gravel fraction. A cluster analysis performed on the heavy mineral results showed five groups of deposits, three of which are related to local glaciers inside the Ruby Range, the other two being related to regional ice lobes of Kluane and Aishihik, respectively. The three groups of local sediments correspond to the three lithologies of the Ruby Range, i.e., the granitic batholith, the schists, and the alaskite. The sediments from the regional ice lobes are characterized by highly diversified mineralogy and petrography and the relative abundance of minerals from the Saint Elias Mountains, the main source of the ice lobes. A correspondance factor analysis performed on the heavy mineral results organizes samples and minerals into a triangular cloud, the three vertices corresponding to biotite, carbonate, and titanite–garnet. These are the key elements of local glaciers, Kluane ice lobe, and Aishihik ice lobe, respectively. Finally, the study shows the extension of Kluane lobe in one valley of the Ruby Range, the ice flow pattern in another valley, as well as a transfluence from Kluane lobe inside the Range.