%0 Journal Article
%A Alonso Azcárate, Jacinto
%A Arche, Alfredo
%A Fernández Barrenechea, José María
%A López Gómez, José
%A Luque del Villar, Francisco Javier
%A Rodas, Magdalena
%T Palaeogeographical significance of clay mineral assemblages in thePermian and Triassic sediments of the SE Iberian Ranges,eastern Spain
%D 1997
%@ 0031-0182
%U https://hdl.handle.net/20.500.14352/57782
%X The evolution of the palaeogeography of the SE Iberian Basin during the Permian and Triassic represents a generalevolution from continental to marine environments. It has been recently studied from the sedimentological,stratigraphical, tectonic and palaeontological points of view. In spite of these results, many aspects of thispalaeogeography are still a matter of discussion. In this study, clay mineralogy analysis complements previous studiesrepresenting a new aspect for understanding the evolution of the sedimentary environment and the palaeogeographyof the Iberian Basin during the periods in question and thus of the palaeogeography and the location of the majorhigh areas in the westernmost border of the Tethys sea.In spite of late diagenetic transformations the original clay mineral associations of the Permian-Triassic sedimentsof the SE Iberian Ranges can be reconstructed. Seventy-seven samples of siliciclastic and carbonate sediments of theseages have been studied (SEM and XRD), revealing six new aspects that help to precise the palaeogeographicalinterpretation of the area:(1) Two major mineral assemblages have been found: illite+ kaolinite +pyrophyllite in the continental facies andillite + chlorite + vermiculite + mixed-layer clays in the marine facies.(2) The Mg-rich clay minerals are here considered to be of marine origin.(3) Active phases of basin boundary faults are marked in the sediments by the presence of pyrophyllite, deriveddirectly from the Palaeozoic metamorphic basement.(4) Unconformities separating major depositional sequences also separate formations with different clay mineralogy.(5) Different groups of clay minerals can be separated clearly coinciding with the different palaeogeographicalstages also distinguished in the westernmost border of the Tethys sea.(6) The clay mineral associations back up the data of a previous hypothesis of a humid climate for the end of thePermian in the study area just prior to the first incursion of the Tethys sea.
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