14 Quaternary Geology and Geomorphology

Saturday, 9 May 2009
8:30 AM - 12:30 PM

BEDROCK GLACIAL LANDFORMS IN THE OKANAGAN VALLEY, BRITISH COLUMBIA, CANADA

Paper number: 14-8
Program: Technical Sessions
Time: 10:50 AM – 11:10 AM

Authors

Abstract

Subglacial landforms have undergone intense scrutiny and reflection for generations, yet consensus on process of their genesis remains elusive. Tests of formational theories often rely on direct observation of landform contents to test whether the process inherit to any land-forming theory is supported by internal sediment content, particularly when the theory involves construction or deformation. When erosion is indicated, then examination of the exterior form may suggest the process involved – particularly whether the process involved plastic or fluid agents.

Several landforms in the Okanagan with partial sections were examined using a form of electrical resistivity mapping with a tool called an Ohm Mapper, that uses and axial dipole array. The tool was deployed over the landforms and dragged with sensor distances at several intervals to produce optimum penetration and subsurface detail. The landforms were mapped using and engineer's level, so that the internal contents could be corrected. The partial exposure provided calibration for the subsurface depths of strata.

Subsurface images revealed that the glacial landforms were covered by only a thin coat of sediment, and that the exterior form was inherited from the bedrock shape. That shape in turn was identical to forms recognized as originating in a subglacial environment, and recognized as being either hummocks or drumlins. These forms are commonly thought to have been created by processes of glacial molding, and/or deposition, but their contents show that neither process could have been responsible. Erosion by plastically-deforming ice is unlikely to have created the landforms because of their specific shapes that suggest turbulent processes were involved. Instead, observations support erosion by large flows of water, and the scale suggests similar volumes to those responsible for creation of similar forms directly to the south, in the Channeled Scablands. If true, then we speculate that these landforms also may indicate large volumes of water flowed turbulently south through the region, and likely contributed to the Scabland flood.