Eskers: Nature, Origin, and Mineral Exploration
Theatre 1 Capitol Theatres
2pm Wednesday 16 November 2016
Dr. Don Cummings
Eskers are commonly sampled during the early stages of mineral exploration campaigns, the idea being that they, like long stream networks in non-glacial settings, have the potential to contain long dispersal-trains and therefore function as “regional dipsticks” for mineral exploration. In this talk, I review the entire body of esker literature and synthesize my own work on eskers to argue the exact opposite: eskers likely rarely, if ever, function as “regional dipsticks” for mineral exploration. Esker dispersal-trains studied to date are short: they are typically no longer than the dispersal trains in the underlying till, from which they are derived, although they can be shifted downflow relative to these till trains by several kilometers. If representative, this observation would appear to help resolve a 100-plus year debate over how eskers form. Specifically, the short dispersal trains in eskers, along with a host of other traits (e.g., lack of downflow widening, lack of downflow fining, lack of large terminal fans, stratigraphic position of esker ridges beneath outwash fans, high degree of segmentation), suggest that eskers form “time-transgressively” in short segments as the ice front retreats, not “synchronously” by aggradation in long subglacial conduits. Eskers must be sampled in order to cover the landscape in its entirety, and they contain on average twice as many heavy minerals as the till, which makes them good targets in low signal-to-noise areas. However, re-evaluation of why eskers are sampled, how eskers are sampled, and how esker data are interpreted is warranted in light of the weight of the data.
Don Cummings is a consulting glacial geologist/clastic sedimentologist and Adjunct Research Professor (Carleton University) based in Ottawa, Canada. For the past 20 years, his work has focused on understanding how geophysical fluids (air, water, glacier ice) interact with the Earth’s surface, the landscapes and deposits generated by these interactions, and the application of this knowledge to resource exploration (minerals, petroleum, groundwater, aggregate) in both glaciated and non-glaciated terrain. Drift prospecting work has brought Don to most parts of Canada, and he has spent multiple field seasons in the Lac de Gras region. His book “The Tide-Dominated Han River Delta” was published in 2016, and he is currently working on a dispersal-train map of Canada. Past awards include Best Oral Presentation (SEPM–AAPG Annual Conference, 2005; mud dispersal in ocean), Exceptional Reviewer (GSA Bulletin, 2009; eskers), and Paper of the Year (Canadian Journal of Earth Sciences, 2013; till dispersal trains).