Prior to the Geological Survey of Canada’s Oak Ridges Moraine study, very few wells were cored through the glacial sediment that overlies bedrock across much of the Oak Ridges Moraine study area. Using a Christensen drilling technique, the GSC study resulted in the drilling of five “Golden Spike” wells that were cored through the entire sediment package down to the bedrock. The advantage of these cored boreholes is that, through detailed logging of the extracted core, it has allowed Quaternary geologists and sedimentologists to more clearly document the depositional environments that were in play during the deposition of the thick accumulation of unconsolidated glacial sediment that lies above the bedrock in the vicinity of the Oak Ridges Moraine.
Since the mid 1990s, the number of PQ cored boreholes has now risen to around 150 boreholes (see Figure below). Most of these have been drilled in the western half of the study area, with many tied to one of several specific projects (i) Ontario Geological Survey hydrogeological studies (largely focused within Simcoe County); ii) Georgetown SWP work, iii) the Southeast collector sewer (SEC) project; or iv) the Vaughan TTC subway extension.
The ORMGP has been involved in a number of these cored boreholes, either by contracting and drilling the boreholes directly, or through numerous partnership arrangements where staff have been on site to assist in collecting, logging and/or documenting depositional conditions related to the extracted sediment. All of the details pertaining to these boreholes are collected and stored in the program’s database. Borehole logs for several of the PQ Cored Boreholes are available for download below.
Locations of PQ cored boreholes in Southern Ontario