Using Short-Transported Tills as a Method of Increasing Mineral Exploration Efficiency in Southwestern Nova Scotia

Abstract

Till is subglacially-derived sediment deposited metres to hundreds of kilometres downflow from its source. In Canada and other glaciated regions, exploration for bedrock ore is challenging due to till coverage, explorationists seek ore-associated minerals or geochemical signatures in tills. However, there is limited exploration procedures optimizing the knowledge that if a mineral or geochemical anomaly occurs in a short-transport till, there is a greater probability of discovering its source. This research focuses on determining how short-transported tills can be identified. Here, I determine if short-transported tills can be distinguished from long-transported tills in southwestern Nova Scotia, improving dispersal tracing in regions with multiple glaciations. Field methods included analyzing clast lithologies, macrofabrics, and bulk densities. Laboratory methods included using radioactive terrestrial cosmogenic nuclides (TCNs) to date surface till in East Kemptville and determine the duration of time that the Salmon River sands were buried. Three boulder samples from East Kemptville yielded a mean age of 15.2 ± 0.4 ka, representing the first use of TCNs to date the deglaciation of southwestern Nova Scotia. A burial sample from the Salmon River Sands contained a relatively high 10Be concentration (1.68x 106 ± 3.74 x 104 atoms/g in quartz), indicating an age can be calculated once 26Al data is available. Future work will process ten additional burial samples from Salmon River and Mavillette to constrain the age of these deposits. Previous surface mapping identified both stony tills and matrix-supported tills in the region. Stratigraphy, geochemistry, and geochronology confirm at least five tills, most are longtransport tills from the north and west. The uppermost till at the Salmon River section (i.e. Beaver River Till) is a short-transported till, another exists above an angular unconformity at the base of the Mavillette section, possibly derived from pre-glacial fluvial or beach gravel deformed by glaciation. By using sedimentology, stratigraphy, geochemistry, and chronology, I evaluate regional tills, assign relative and numerical ages, linking them to paleo-ice flow dynamics and classify them as a short- or long-transport till. I conclude with a discussion of a field strategy for explorationists to establish if they are sampling short-transport tills.