LOCAL TO CONTINENTAL-SCALE THREE-DIMENSIONAL GEOLOGICAL MODELING OF QUATERNARY SEDIMENTS: A MULTI-FACETED CHALLENGE (Invited Presentation)

Three-dimensional geological models of Quaternary sediments are increasingly needed for various water-related investigations, from the local contaminated site to watershed studies and continental-scale water resources assessments. Technological developments have had a profound impact, especially visualization and geophysical techniques, but the shallow subsurface (10-100 m) remains a geological frontier. As a result, the need for 3D information is increasing more rapidly than high quality 3D models can be produced. Geological models have always depended on the amount and quality of the data available, but also on the degree to which these different data sets have been integrated and interpreted; mapping intricate and highly heterogeneous Quaternary sediments thus requires more than databases. Integration of different datasets (e.g. surficial maps, borehole data, geophysical data), but also expert knowledge (e.g. stratigraphic frameworks, earth surface processes) is at the heart of integrated geomodeling. Selected local to continental-scale geomodeling situations are analyzed, with emphasis on challenges and problems that often arise while mapping the subsurface in complex geological settings, in populated areas and across multiple jurisdictions.