QUATERNARY STRATIGRAPHY OF THE ABERDEEN LAKE REGION, CENTRAL NUNAVUT, WITH IMPLICATIONS FOR THE EVOLUTION OF THE KEEWATIN SECTOR OF THE LAURENTIDE ICE SHEET

The Aberdeen Lake region of central mainland Nunavut is characterized by cross-cutting streamlined glacial landform flowsets and near continuous till blanket. Detailed logging of 62 continuous cores of Quaternary sediment from Cameco Corporation facilitates in a major way the study of the Quaternary record of this remote region. Sedimentological and stratigraphic analyses of these cores is coupled with mapping of outcrop ice flow indicators, river bluff investigation, remote mapping of glacial lineations and clast lithology counts to understand the glacial dynamics and till provenance of the region. Ice flow indicator mapping across the study area reveals a complex ice flow record reflecting changes in the configuration of the Laurentide ice sheet. Core logging reveals variable Quaternary sediment thickness throughout the study area, with till thickness reaching a maximum of 37 m. This investigation has revealed multiple till units over drilling targets with varying till provenance reflecting the complex surficial ice flow record. This is supported by clast lithology counts which have identified a till unit interpreted to have been deposited by the earliest recognized ice flow phase in the region, which was towards the west-southwest. Clast counts reveal a complex till stratigraphic record with diamicton deposited by near opposite ice flow phases appearing very similar in drillcore and highlights the necessity for the use of clast lithology counts and geochemistry as a stratigraphic discriminant within this region. A non-glacial lacustrine unit intersected at the base of a drillhole and below thick till is tentatively assigned to the last interglacial in the area (Sangamonian), although it is currently constrained only by a non-finite radiocarbon age and normal magnetic polarity. The occurrence of relatively continuous and thick till on the Canadian Shield raises a number of questions about timing of till production phases and overall glacial dynamics’ evolution of core regions of ice sheets during a full glacial cycle. These findings are also being incorporated into tracing dispersal trains in 3D from known subcropping alteration zones associated with uranium mineralization and will have implications for future drift prospecting in the region.