COMPLEXIDADE EM SISTEMAS DEPOSICIONAIS

Abstract

COMPLEXITY IN DEPOSITIONAL SYSTEMS. Depositional systems comprise sedimentary processes acting in different space and time scales. These systems show complex dynamics and generate products of high variability, the sedimen- tary deposits, whose elementary blocks are the depositional facies. The understanding of facies distribution within sedimentary deposits is of great importance to historical geology and to mineral exploration or petroleum production. Thus, it is necessary to understand depositional systems dynamics not only in the time scale of processes that can be directly observed, but in all time scales comprised by depositional systems lifetime. Facies models formulated through observation of modern depositional systems do not consider the scale aspect. Thus, they are more adequate to classification purposes than to the understanding of depositional systems dynamics. The use of facies models to interpret the sedimentary record is based on the assumption that sedimentary facies materialize sedimentary process. However, distinct processes can produce the same facies. Furthermore, the production, erosion, transport and deposition of sediments are irregular and discontinuous along time, giving incomplete character to the sedimentary record. Therefore, ambiguity and discontinuity must be considered when the sedimentary record is described by facies models. The understanding of the variability of sedimentary deposits will be possible through the knowledge of depositional systems dyna- mics that should be studied in a more preditive and relational way, distinct of the analogical and descritive way commom adopted in