Geophysical Imaging Of Palaeokarst Features And A Kaolinite Deposit At Sylvan, Manitoba, Canada

Geophysical surveys were performed at Sylvan, Manitoba, Canada to investigate<br>palaeokarst features in the Palaeozoic bedrock. Depressions in the bedrock surface host a<br>Cretaceous kaolinite deposit containing zones of kaolinite, silica sand and lignitic clay. The<br>bedrock surface and kaolinite deposit lie beneath l-5 m of glacial overburden. Terrain<br>conductivity, VLF-EM, time-domain electromagnetics, and DC-resistivity surveys were<br>conducted to map the enhanced electrical conductivity associated with the deposit. Results<br>indicate that the deposit has a bulk electrical conductivity of 13-25 mS.m’ consistent with low<br>cation exchange capacity of the kaolin. The geophysical surveys, which were performed at a<br>range of scales over a total area of several square kilometres, indicate that the palaeokarst surface<br>consists of discontinuous, sinuous, depressions of variable depth. Results suggest there are only<br>a few locations in which the depth to the bedrock (and therefore the thickness of the kaolinite<br>deposit) exceeds 5 m.