The transition to 3D, web-accessible geological mapping
|Location||International Geological Congress,oslo 2008|
|Holding Date||29 September 2008|
We all require geological mapping to fulfill objectives related to health, heritage, safety, and economic development, and we increasingly expect public information to be web-accessible and readily usable. Maximum benefits will be conveyed if user interfaces are competing to make available a database of national if not international information on subsurface conditions. We therefore require a comprehensive database depicting bathymetry, soil mapping, onshore and offshore surficial and bedrock geology, and 3D geology depicting extent, thickness, and properties of undeformed strata, such that all undeformed strata are removable from map depictions, and so that drillhole forecasts down to deformed rocks can be issued for any point. To implement what technology now permits, legacy maps must be digitized and reconciled, with multiple generations of legends being categorized in part through thorough content analysis. The synthesis will require digitizing, reconciliation, and assembly of topography, bathymetry, offshore geology, soils, surficial geology, all public domain drillhole and geophysical data, bedrock maps, and existing stratigraphic models typically expressed as structure contours. New 3D mapping will require benchmark information from cored holes logged by geologists as well as geophysical surveys. These high-quality results are extrapolated laterally using drillhole data, commonly large quantities of water well data of varying resolution and reliability. Much effort is required to adequately georeference the drillhole data, and to parse large numbers of unique lithological descriptions. Stratigraphic modeling methods ideally use all data and an approach that permits judgment in the acceptance or rejection of data, while interpolation and extrapolation are guided by expert judgment based on the best available insights into process and history. Models are best captured as a regular grid of profiles that convey expert opinion on interpolation and extrapolation from the data points. Reconciliation of mapping with neighbouring jurisdictions is required, as is balancing subjective definition of strata with more objective geostatistical approaches to characterizing the heterogeneous physical properties. Databases of observations and measurements can be retained with the interpreted model, and models can be assigned varying confidence levels such that the result is seen not as an end but a means for prioritizing new mapping. Pressing user requirements demand that geological survey work advance as rapidly as possible, from paper maps in libraries to web-accessible databases, from project publications to regularly-updated, version-numbered, multi-jurisdiction databases, from plan view maps to interactive drillhole databases and 3D models, and from static depictions to dynamic models such as groundwater flow models.