Exemple de modèle sédimentaire de plate-forme tempérée stable : la marge continentale supérieure de la Provence

Abstract

Description of the biosedimentary zonation of a stable Provence margin (upper zone : 0 to -60 meters). The coherence of the transitional system (passages) is complicated with the inadaptability of some sedimentary facies to the benthic communities. This leads us to discuss about the variable treatment and many sorts of evolution processes controlling the nature, limits and sedimentary distribution. Through the factorial analysis, we try to interpret the natural and complex structures : erosional sub-marine phenomena (sea-grasses) and muddy gradients. The research of the main and the most discriminant variables as their range, results in a hierarchic clustering and an automatic classification of many sedimentary deposits : mobile " infralittoral " sands, sand and biogenic gravels and mudstones. The actions of maladjustment are analysed : mechanical submarine bottom-erosions, progression of the mud line, retroaction ("feed-back") effects (Posidonian sea-grasses). The model elaboration is made up of several successive stages : 1 . Inputs : state variables and variables acting at every level of the system ; 2. "entrance box" : initial input assemblages, raw data and complementary variables ; 3. "exit box" where three bodies are exposed : — mobile " infralittoral " sands, — biogenic sands and gravels in relation to "infra" and "circalittoral" levels, muddly environments, Prevision of their evolution. 4. Consequences : critical remarks and decision.