Developing the bedrock layer for Canada 3-D: the Precambrian-Phanerozoic boundary
Authors: de Kemp E A , Schetselaar E M , Hillier M , Montsion R 
Published: June 2017

One of the most significant tectonostratigraphic features of the geology of Canada is the boundary separating 'cover' rocks of the Phanerozoic Eon and older 'basement' rocks; dominantly metamorphic and crystalline rocks of the Precambrian shield. In the context
of the Canada-3D initiative to develop a 3D geological model of Canada from the surface to the Moho, we have begun to integrate data constraints for modelling this boundary, including geological map, drillhole and seismic data. The 3D surface development is being undertaken through the application
of data (geostatistical, implicit modelling (GOCAD/SKUA and SURFE) and knowledge (SPARSE) driven methods. More accurate 3D delineation of this key boundary will help support applications such as the separation of bulk rock properties into cover and basement classes which could in turn be used for
geophysical and mineral potential modelling. Coupled with heat flow and fracture density estimates; it could also contribute to future development of national-scale 3D favourability maps for geothermal energy and CO2 sequestration potential. The project combines a large amount of data from various
sources collected over the last 175 years since the initiation of geological mapping by the Geological Survey of Canada in 1842 by Sir William Logan.
The Precambrian-Phanerozoic boundary is dominantly an angular unconformity between the crystalline bedrock of the Canadian Shield and Phanerozoic sedimentary cover sequences, spanning a hiatus of several hundreds of millions to more than two billion years. In rare cases such as the Rapitan Group in
the Mackenzie Mountains, it is a more conformable stratigraphic contact between Neoproterozoic and Cambrian formations. There are also many parts of Canada's subsurface which have no geologic record of the boundary where the crust is mainly composed of either younger Paleozoic and Mesozoic mobile
belts (Central Newfoundland and British Columbia), or exposed basement of the Precambrian Shield. The geological data that constrain the Precambrian-Phanerozoic interval are spatially heterogeneous, and vary in quality from excellent observations from petroleum wells in the Western Canada and
Williston Basins, to less reliable well logs in Southern Ontario, to interpretive map traces in the overburden covered Hudson Bay low lands. Seismic reflection and refraction data from Lithoprobe and industry surveys will support deeper interpretations of the boundary, and be integrated with
constraints obtained by geological mapping in the more complex regions of the Canadian Cordillera and Appalachian orogens. Canada-3D is modelling other tectonostratigraphic features (crustal scale fault networks and major lithostratigraphic horizons) within the bedrock layer, above and below the
Precambrian-Phanerozoic boundary, but by focusing early on this significant boundary we gain insight to the data distribution, the required methodology and processing gaps that exist tackling this problem at a national scale. As the project proceeds there will be a need for development of 3D tools
to support uncertainty estimation, sparse data interpolation and extension, and interpretation workflows designed to cope with the many challenges presented by limited sampling of complex geologic terrains.