Middle-Upper Triassic stratigraphy and structure in the Alt Palància region (eastern Iberian Chain): A multidisciplinary approach

Abstract

The present study provides new data of the Middle-Upper Triassic successions and their deformation in the eastern Iberian Chain, where contractional tectonics during the Cenozoic disrupted this Mediterranean type of Triassic rocks. The succession, divided into three Muschelkalk units, was studied in the Alt Palància area. In this area, both the lower and upper Muschelkalk consist of two main types of sub-units, those made up of carbonate and those of carbonate-marl alternation. The marked similarity observed between the evaporite units of the middle Muschelkalk and the Keuper humpers their unambiguous discrimination in the field. The integration of geological mapping, stratigraphic logging, palynological dating and gypsum isotope analysis carried out provided that: i) a change in the structural style, facies, and depositional thickness occurs across a SW to NE transect at both sides of the Espina-Espadà Fault, providing evidence for the extensional activity of this major structure; ii) palynological data assign Anisian age to the Röt facies and the lower and the middle Muschelkalk units, and Ladinian to the upper Muschelkalk unit; iii) the δ34SCDT and δ18OSMOW values of gypsum reveal as a useful proxy to discriminate between the middle Muschelkalk (δ34S: 15.6 to 17.8‰) and the Keuper (δ34S: 14 to 15.5‰) units; and iv) the isotopic signature also helps to identify clayey-marly-gypsiferous outcrops made up of the two evaporite facies due to tectonic juxtaposition. These results confirm the Mediterranean type of Triassic rocks for the entire Alt Palància and other areas to the NE. This multidisciplinary approach reveals as a robust methodology to study Triassic basins in Iberia and to other geological domains where the carbonate-evaporite successions have been greatly disrupted by tectonism.

The Anisian continental-marine transition in Sardinia (Italy): state of the art, new palynological data and regional chronostratigraphic correlation

“…As the transgression progressed, during the Pelsonian/Illyrian, there was a gradual evolution to a more transitional marine environment. Following this new sea level rise, related to the northward shift of Cimmeria (Escudero-Mozo et al, 2014, more areas were progressively covered by epicontinental seas, including the southernmost sector of Sardinia (Sulcis-Iglesiente region), while Minorca and the northern Catalonian basin (Escudero-Mozo et al, 2014 and the eastern Castellón area (López-Gómez et al, 1998;Escudero-Mozo et al, 2015;Ortí et al, 2020) in eastern Iberia were still represented by continental elevated areas during the middle Illyrian (Fig. 12).…”

“…11c). The new transitional pulse that took place during the middle-late Illyrian represented the complete incursion of the Tethys sea in its western domain, including central-eastern Iberia and the Balearic Islands, as well as most of Central and Southern Europe (Gianolla & Jaquin, 1998;Ziegler, 1999; Sanz De Galdeano et al, 2001;Martín-Algarra & Vera, 2004;Pérez-López & Pérez-Valera, 2007;Martín-Rojas et al, 2009;Mercedes-Martín et al, 2013;Escudero-Mozo et al, 2015;Ortí et al, 2020). Over the course of this step, the evaporitic conditions (sabkha environment) which characterized most of the upper Anisian in Sardinia eventually gave way to a shallow marine environment in the whole island.…”

Salt tectonics vs. inversion tectonics: The anticlines of the western Maestrazgo revisited (eastern Iberian Chain, Spain)

“…Diagenetic dissolution of evaporite sequences (probably including anhydrite levels) provided ideal conditions for the formation of the widespread Hettangian collapse-breccia (e.g. Aurell et al, 2007;Bordonaba & Aurell, 2002;Gómez et al, 2007;Hernández et al, 1985;Ortí et al, 2017Ortí et al, , 2020. 6.1.3 | Remarks on the 'Jurassic-Early Cretaceous unconformities related to diapiric uplift'…”

“…Middle Triassic to Early Jurassic evaporite-bearing successions shows limited thickness in the eastern Iberian realm. In most cases, Middle Muschelkak and Keuper facies are <150 m thick, and thin evaporitic beds (mostly <10-15 m thick gypsum beds) are intercalated between thick peritidal red mudstones (Table 1;Marín, 1974;Ortí et al, 2017Ortí et al, , 2020Pérez-López et al, 2021). However, within the Maestrazgo basin, a vertical, apparent thickness of evaporites up to 1200 m has been drilled (i.e.…”

“…The eastern Iberian Chain is one of many examples in the western Mediterranean in which salt tectonics has been applied to explain the origin of pre-compressional sedimentary basins and their subsequent evolution (Vergés et al, 2020). This mountain belt contains certain structural features that at first glance fit with the definition of a 'diapiric province': (i) numerous outcrops of Triassic rocks containing evaporites (mainly gypsum, Ortí et al, 2017Ortí et al, , 2020 and sub-surface data documenting salt (Lanaja, 1987), (ii) complex folding directions interfering with the regional contractive trends have implications to assess ongoing reinterpretations in terms of salt tectonics in other alpine basins and ranges of the western Mediterranean.…”