Publication: A comparison of the Iberian and Ebro Basins during the Permian and Triassic, eastern
Spain: A quantitative subsidence modelling approach
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Publication Date
2009
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Elsevier B.V.
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Abstract
The Permian–Triassic sediments of the Iberian Plate are a well studied case of classical Buntsandstein–
Muschelkalk–Keuper facies, with good sedimentological interpretations and precise datings based on pollen
and spore assemblages, ammonoids and foraminifera. Synrift–postrift cycles are recorded in these facies, but
there are only a few studies of quantitative subsidence analysis (backstripping method) and only a previous
one using forward modelling for the quantification of synrift–postrift phases of this period.
Here we present the results obtained by the quantitative analysis of fourteen field sections and oil-well electric
log records in the Iberian and Ebro Basins, Spain. Backstripping analysis showed five synrift phases of 1 to
3 million years duration followed by postrift periods for the Permian–Triassic interval. The duration, however,
shows lateral variations and some of them are absent in the Ebro Basin. The forward modelling analysis,
assuming local isostatic compensation, has been applied to each observation point using one-layer and twolayer
lithospheric configurations. The second one shows a better fit between observation and model prediction
in a systematic way, so a two layer configuration is assumed for the sedimentary basin filling analysis.
Lithospheric stretching factors β and δ obtained in the forward modelling analysis are never higher than 1.2,
but sometimes βb1 and simultaneously δN1 in the same section. If surficial extension is compensated by deep
compression either at the roots of the rift basins or in far-away zones is not yet clear, but this anomaly can be
explained using a simple shear extensional model for the Iberian and Ebro basins.