IAMG 2001--Cancún Technical Program--Session I

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The Geological Reference System of France--2D and 3D imaging--2001-2005 priorities by Patrick Ledru, Denis Bonnefoy, Jacques Demange, and P. Nehlig,* BRGM, France The core of the French Geological Survey's (BRGM) mission is to improve our knowledge of France's geological infrastructure through the acquisition and processing of geological and geophysical data, through monitoring the Earth's dynamics and its effects, through modeling and disseminating Earth-Science information in the form of maps and models, etc.--i.e. fundamental research projects based on strong scientific and methodological foundations. The achievements of two national research programs developed in partnership with universities and other research institutes--GéoFrance 3D (to be completed in the fall of 2000) and the 1:50,000-scale Geological Map of France program (1st edition due to be completed in 2006)--have provided the basis for a revised geological framework that we term the Geological Reference System of France and that, for many areas, is supported by geophysical surveys. Thus a global scheme has been defined, enabling priorities to be formulated for the 2001-2005 plan. The program will federate projects devoted to research and Public Service, with the objective of providing information on and access to data concerning the nature and properties of rocks at any point in the country's 3D space. Making full use of Geographic/Geologic Information Systems (GIS), and other modeling software, requires a unified coverage of digitized maps. Therefore, in a first stage (2001-2003), the earlier 1:50,000-scale geological maps will be digitized even though the legends, symbols and references may vary between maps, depending on the scientific concepts used. At the same time (2001-2005) our knowledge of the country-scale geological systems will be updated through the production of geological and geophysical maps at 1:250,000 scale; this will provide: (i) a synthesized framework available for further harmonization of the 1:50,000-scale maps, and (ii) research projects, defined in partnership with universities, on pending scientific questions. Plotting the physical properties of rocks is primordial for modeling the physical behaviour of the soil, surface and subsurface; such programs are ongoing and will be extended in order to update the full coverage of France. Quantifying permeability parameters, interpreting high-resolution radiometric and aeromagnetic surveys, etc., provides new datasets that can be interpreted, inverted, correlated and combined for a probabilistic approach to 3D geological and geophysical imaging--the future "3D" generation of geological maps--adapted to the use of decision-makers for management and environmental purposes. Finally, a 3D platform for exchanging geological and geophysical data is required for achieving the aims of providing access to data on the nature and properties of rocks at any point of the country's 3D space. New 3D modeling tools have been designed, tested and developed to answer the needs of model builders and users. In addition, recent advances in communications means that the dissemination of information and models can be done through the Internet, using languages and formats such as Java or VRML. An Internet site, InfoTerre, containing information and data concerning France's geological maps, as well as borehole and gravimetric databases (among others), has already been developed (http://infoterre.brgm.fr). This is in the process of being extended to incorporate all the datasets acquired in the framework of BRGM's Earth Science activities and should, in the near future, give access to on-line services for end-users.