Lobal affinity of Late Wisconsin tills at St. Marys in southwestern Ontario, Canada

The exposures at the St. Marys Cement Inc. quarry at St. Marys, Ontario, have been studied by geologists since the mid-1950s. This paper summarizes previous and new information collected in 2009, 2010, and 2012 and discusses the record of sediments resting on the bedrock surface that have been exposed during quarry operations. The exposed sediments illustrate the dynamic behavior of the Laurentide Ice Sheet in this area during the Late Wisconsin. Evidence for subglacial meltwater activity, shifting ice-flow directions during till deposition, a local or regional erosion event, possible subaerial exposure, and ice-marginal sedimentation is observed in the sequence of tills and stratified sediments exposed in the quarries. It also highlights how rapid lateral facies changes, complex contact relationships, and steep erosional contacts can prove to be challenging for correlation and extrapolation of subsurface units into three-dimensional stratigraphic models. Fourteen units were identified of which the lower ...