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

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Author: Vargas, H. · Gaspar-Escribano, J.M. · López-Gómez, J. · Wees, J.-D. van · Cloetingh, S. · Horra, R. de la · Arche, A.
Type:article
Date:2009
Source:Tectonophysics, 1-2, 474, 160-183
Identifier: 241724
doi: doi:10.1016/j.tecto.2008.06.005
Keywords: Backstripping · Extensional basins · Forward modeling · Subsidence analysis · Ammonoids · Backstripping · Ebro basin · Extensional basins · Forward modeling · Forward modelling · Isostatic compensation · Lateral variations · Lithospheric · Model prediction · Observation point · Permian · Quantitative analysis · Rift basin · Sedimentary basin · Sedimentological interpretations · Simple shear · Syn-rift · Triassic · Triassic sediments · Two layers · Oil wells · Sedimentology · Sediments · Subsidence · comparative study · compression · extensional tectonics · facies analysis · forward modeling · isostasy · Permian · quantitative analysis · rifting · sedimentary basin · sedimentary sequence · sedimentology · subsidence · Triassic · Ebro Basin · Eurasia · Europe · Iberian Basin · Iberian Peninsula · Southern Europe · Spain · Ammonoidea · Foraminifera

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 two-layer 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 β < 1 and simultaneously δ > 1 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. © 2008 Elsevier B.V. All rights reserved.