INVESTIGATION OF THE INFLUENCE OF LITHOLOGICAL VARIABILITY ON EROSION OF THE NIAGARA ESCARPMENT IN HAMILTON, ONTARIO, CANADA

The Niagara Escarpment, known locally as the ‘Hamilton Mountain’, is a major geomorphic feature that dissects the City of Hamilton, Ontario. The escarpment, formed primarily by glacial and fluvial erosion processes during the Quaternary, exposes Silurian to Ordovician-age sedimentary rocks consisting of interstratified dolostones, limestones, sandstones and shales. Erosion processes along the escarpment continue to the present day but are poorly understood, and are causing numerous issues relating to the maintenance of access routes built on the escarpment face since the settling of the city in the mid 1800s. Recent rockfall events have resulted in frequent road closures and emphasize the need for enhanced understanding of erosion processes along the escarpment and factors influencing their rate and severity.

This poster presents the results of an investigation into the sedimentological and structural variability of lithologic units exposed along the escarpment in Hamilton and their influence on erosion processes. Within the Hamilton region, the escarpment consists of up to ten distinct lithologic units, ranging from resistant caprock dolostones of the Lockport Formation, to easily eroded shales of the Rochester and Queenston formations. The interstratification of these lithologic units results in differential erosion patterns that change both vertically and laterally. Data regarding the sedimentological characteristics (including unit composition, structures, bed thickness), facies architecture (lateral and vertical unit geometries), and fracture patterns, of lithological units exposed at nine sites along the escarpment in Hamilton will be presented and related to potential erosion processes. Factors that influence both erosion processes and rates include lateral and vertical changes in the composition, structure and thickness of lithologic units, fracture spacing and its influence on hydrologic processes and the effectiveness of freeze-thaw cycles, and anthropogenic changes to the escarpment. Enhanced understanding of lithological variability along the escarpment and the identification of potential factors impacting erosion rates, will allow the implementation of effective remediation strategies to protect infrastructure crossing the Niagara Escarpment in Hamilton.