Modélisation de l'évolution géologique d'un paléosite à l'échelle de la centaine de milliers d'années: exemple du Jarama (Espagne)

Manuel Garcin (1) , Carmen Bajos (2) , Carlos del Olmo (2) , Pierre Godefroy (1) , Pierre Peaudecerf (1)

1 BRGM - Bureau de Recherches Géologiques et Minières (BRGM)
2 ENRESA - ENRESA

The objective of this study, carried out as part of EEC Project No. F12W-CT91-0075, entitled "Paleoclimatological revision of climate evolution and environment in Western Mediterranean Regions", was to reconstruct the geological evolution of a test area (the Jarama paleosite, Spain) over the past 120,000 years (Eemian to Present). This site, even though it did not meet all the criteria necessary for a waste repository, was chosen for its representativity of geological conditions likely to be encountered in more suitable areas of Spain. The basic principle of this study was to assess the repercussions of fundamental hypotheses of global evolution on phenomena of regional scale (scale of the paleosite representing several hundred square kilometres) through integrating the interactions of these phenomena. To this end we used the techniques of Artificial Intelligence and qualitative reasoning developed and used in the BRGM Expect Project. The methodology followed consists, in the first instance, in making as exhaustive an inventory as possible of the geological phenomena that occur at both global scale (eustatic variations, temperature variations, etc.) and regional scale (erosion, alluvial terrace deposition, variation in vegetation, etc.). This inventory is based as often as possible on field studies from other modules of the project (ITGE 1993), as far as regional scale phenomena are concerned, and on literature sources for global scale phenomena. A quantitative evaluation of selected major processes is then carried out so as to obtain an order of magnitude for the rates of these phenomena. The next phase consists in a detailed analysis of the phenomena and the parameters to be considered. It more particularly concerns the interactions of the phenomena and the modalities of these interactions. This analysis uses the taxonomy and formalism developed within the Expect Project (Garcin et al. 1994). The relationships are defined qualitatively or quantitatively, depending on our degree of knowledge. This phase enabled a specific conceptual diagram to be drawn up for the Jarama paleosite, integrating the different processes considered to have an influence. Fundamental hypotheses of global evolution are then applied to this conceptual diagram and expanded according to the laws of causal relationships. This phase, which is the simulation sensu stricto, provides parameter-evolution scenarios (histories). The sensitivity of the modelled system is analysed against the histories derived from several scenarios developed from different fundamental hypotheses of evolution or from different nodal characteristics of the conceptual diagram.

Mots clés: stockage; Géoprospective; simulation; EXPECT; Intelligence Artificielle

Domaines: Informatique; Sciences de la Terre

Manuel Garcin, Carmen Bajos, Carlos del Olmo, Pierre Godefroy, Pierre Peaudecerf. Modélisation de l'évolution géologique d'un paléosite à l'échelle de la centaine de milliers d'années: exemple du Jarama (Espagne). Colloque Géoprospective, 1994, Paris, France. 12 p. ⟨hal-00562519⟩