The Halton "Deformation": Till: An Application of G.I.S. Basin Analysis Accompanied by a Sedimentological Examination of the Halton Basal Contact

Abstract

<p>The combined use of powerful computers and Geographic Information System (G. I. S.) technology has only recently been utilized as a geological tool in the study of unconsolidated sediments. G. I. S. is applied in mapping the bedrock topography and the geometry of the Halton Till in the Toronto region identifying the technology as an essential component of any basin-wide investigation.</p> <p>The bedrock surface exhibits a strong control over the distribution of the Late Wisconsin aged Halton Till. The wide, deep Laurentian channel contains thick sequences of Mid Wisconsin sediments and is capped by a thin veneer of Halton Till. The highland areas on the flanks of the Laurentian channel contain many small bedrock channels oriented in a NW/SE trend parallel to ice flow in the Late Wisconsin. These smaller bedrock channels are often the sites of thick deposits of Halton Till.</p> <p>A sedimentological investigation of the Halton Till basal contact in outcrop reveals strong evidence of underlying sediments into the Halton Till. Sediment rafts, deformed basal zones in the Halton Till and sheared underlying sediments suggest that the traditional classification of the Halton Till as a lodgement complex is incorrect.</p> <p>A grainsize investigation of the lower 10 meters of the Halton Till supports the outcrop evidence of the incorporation of underlying sediments into the lower Halton Till. The lithology of the underlying unconsolidated sediments have a strong control on the grainsize distribution of the lower 4 meters of the Halton Till.</p> <p>The geometry of the Halton Till, its sedimentology, grainsize distribution and glacitectonic deformation of underlying units all provide evidence for the deposition of the Halton Till as a 'deformation till'. Present investigations of the Halton Till as a potential unit for the location of waste disposal sites should take into consideration the geometry and sedimentology of the till.</p> <p>G.I.S. is a rapidly expanding field and it will play an important role in the study of Quaternary sediments (particularly aquifers) and the location of future hazardous waste disposal sites in Southern Ontario.</p>