A comparison of the Iberian and Ebro Basins during the Permian and Triassic, easternudSpain: A quantitative subsidence modelling approach

摘要

The Permian–Triassic sediments of the Iberian Plate are a well studied case of classical Buntsandstein–udMuschelkalk–Keuper facies, with good sedimentological interpretations and precise datings based on pollenudand spore assemblages, ammonoids and foraminifera. Synrift–postrift cycles are recorded in these facies, butudthere are only a few studies of quantitative subsidence analysis (backstripping method) and only a previousudone using forward modelling for the quantification of synrift–postrift phases of this period.udHere we present the results obtained by the quantitative analysis of fourteen field sections and oil-well electricudlog records in the Iberian and Ebro Basins, Spain. Backstripping analysis showed five synrift phases of 1 toud3 million years duration followed by postrift periods for the Permian–Triassic interval. The duration, however,udshows lateral variations and some of them are absent in the Ebro Basin. The forward modelling analysis,udassuming local isostatic compensation, has been applied to each observation point using one-layer and twolayerudlithospheric configurations. The second one shows a better fit between observation and model predictionudin a systematic way, so a two layer configuration is assumed for the sedimentary basin filling analysis.udLithospheric stretching factors β and δ obtained in the forward modelling analysis are never higher than 1.2,udbut sometimes βb1 and simultaneously δN1 in the same section. If surficial extension is compensated by deepudcompression either at the roots of the rift basins or in far-away zones is not yet clear, but this anomaly can beudexplained using a simple shear extensional model for the Iberian and Ebro basins.