La Formación Cehegín y la Formación Siles se han definido para caracterizar los carbonatos de facies Muschelkalk que afloran en las Zonas Externas de la Cordillera Bética. Estas formaciones caracterizan los sedimentos depositados en el Paleomargen Sudibérico durante el Triásico Medio. Sus facies sedimentarias corresponden a depósitos de una plataforma epicontinental, que en su primera etapa presentaban rasgos de rampa en sus márgenes. Esta plataforma fue evolucionando y sus depósitos fueron reflejando cada vez más sus rasgos de plataforma epicontinental de aguas poco profundas donde no eran frecuentes los depósitos de alta energía salvo durante las tormentas. Se trataba de un extenso mar epicontinental con escasas barreras, que hacia el este daba paso al mar del Tethys.
Facies, 2008. Vol. 54, 61-87.
Stratigraphy and sedimentology of Muschelkalk carbonates of the Southern Iberian Continental Palaeomargin (Siles and Cehegín Formations, Southern Spain)
Fernando Pérez-Valera · Alberto Pérez-López
ABSTRACT
The Triassic sediments of the External Zones of the Betic Cordilla were deposited on the Southern Iberian Continental Palaeomargin. Two coeval Ladinian formations, namely the Siles Formation and the Cehegín Formation, are described to illustrate the facies and lithostratigraphic variability in the Muschelkalk carbonates. There has been some dispute over the number of carbonate units present in the Siles Formation. Our studies assign a tectonic origin to these recurrent carbonate units. Both formations comprise only one carbonate unit, which is correlated to the Upper Muschelkalk of the Catalan and Germanic basins and some Iberian Range sections. To characterize the sedimentological features of these formations, 14 facies were defined. The most widespread sediment was originally lime mud, although bioclastic deposits are also common. In the facies succession, a main transgressive-regressive sequence could be identified. According to the facies model proposed here, a muddy coastal and shallow-water platform prograded over mid ramp deposits. There is no evidence for a seawards reefal or oolitic-bioclastic sandy barrier. The most significant feature of this sedimentary interpretation is that these carbonate facies show clear characteristics of an epicontinental platform.
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Las facies Muschelkalk se extienden por casi todos los afloramientos de la Península. Presenta facies muy similares pero, al mismo tiempo, existen variaciones de una subcuenca a otra. Una constante de estas facies es su carácter somero. Los depósitos más frecuentes en algunos afloramientos son de tipo costero, llanuras de mareas y extensos lagoons que conforman una paleogegrafía compleja, que difiere con los modelos de plataformas con cinturones de facies.
Sedimentary Geology 420 (2021) 105904
Middle Triassic carbonates of Eastern Iberia (Western Tethyan Realm): A shallow platform model
Alberto Pérez-López, Constantino Benedicto, Federico Ortí
ABSTRACT
Much of the eastern sector of the Mesozoic Iberian basin belongs to the ‘Mediterranean type’ Triassic. This type is characterized by a Middle Triassic stratigraphic record comprised of two carbonate Muschelkalk units (lower and upper) separated by a detrital-evaporite middle Muschelkalk unit. In the present study areas, the two first marine flooding episodes of the Middle Triassic led to the deposition of extensive shallow-water carbonates on a block controlled epicontinental platform in the lower and upper Muschelkalk units. These carbonates were part of third-order transgressive–regressive sequences. The two carbonate sequences display similar vertical facies and stratigraphic sub-unit arrangements. The base of the two sequences is marked by a (lower) carbonate marl alternation, which was deposited in mixed tidal flat-to-lagoon settings. In the middle of the sequences, the carbonate character is predominant and facies associations mainly suggest shallow waters and high environmental variability. The change froma transgressive to regressive trend occurs in the middle of the sequences, although the position of the maximum flooding zone can vary fromone to another stratigraphic section. The tops of the sequences show two different lithological assemblages, which are coeval and grade laterally to each other. One assemblage is a ‘carbonate terminal complex’ formed by tidal flat and sabkha deposits,which is predominant in the lower Muschelkalk unit. The other assemblage is a lagoon-peritidal (upper) carbonate-marl alternation, predominant in the upper unit. Together, the two sequences suggest a complex platform morphology with a mosaic facies distribution, which evolved from a not very high energy ramp-like profile (transgressive phases, TST) to a lower energy rimmed shelf, ending with tidal/lagoon environments (regressive phases, HST). Facies associations, however, suggest some what deeper depositional settings for the upper than lower Muschelkalk unit. Here we compare the two carbonate units in the study areas with those described in the literature from other Triassic basins of Eastern Iberia and the SW Germanic Basin, all forming part of the Peri-Tethys area of the Tethyan Realm.
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El estudio continuado en los diferentes afloramientos de carbonatos del Triásico ha permitido descubrir y caracterizar una nueva formación de facies Muschelkalk, pero de edad Anisiense. Se trata de los carbonatos del Muschelkalk inferior que no habían sido identificados hasta ahora en la Zona Externa de la Cordillera Bética. Presenta depósitos de facies muy someras, aunque presenta dos intervalos de sedimentos lutíticos, que corresponden a ingresiones marinas, con fósiles que han permitido datar esta formación. La interpretación de estos carbonatos ha supuesto un avance en la reconstrucción paleogeográfica del Anisiense, para la cuenca Bética.
Sedimentary Geology 449 (2023)
First record of Anisian deposits in the Betic External Zone of southern Spain and its paleogeographical implications
Fernando Pérez-Valera, Alberto Pérez-López, Annette E. Götz, Sonia Ros-Franch, Ana Márquez-Aliaga,
José Francisco Baeza-Carratalá, Juan Alberto Pérez-Valera
https://doi.org/10.1016/j.sedgeo.2023.106374
ABSTRACT
In the External Zone of the Betic Cordillera (S Spain), upper Muschelkalk (Ladinian) facies have been known for decades; however, so far there is no stratigraphic record of Anisian deposits. In the present study, new biostratigraphic data from a carbonate succession in the easternmost Subbetic domain reveal a Pelsonian-Illyrian (Anisian) age. The nautiloids Germanonautilus salinarius and Germanonautilus saharonicus are documented for the first time in the Iberian Peninsula, and together with the brachiopod Tetractinella trigonella and the bivalves Neoschizodus orbicularis and Myophoria vulgaris they represent marker fossils of Anisian deposits previously described from many other basins, both in the Germanic and Alpine realms. The co-occurrence of the nautiloid G. saharonicus and the bivalve Gervillia joleaudi at the top of the studied succession serves as correlation tool for the first faunal migration event from the Sephardic towards the Subbetic domain. The palynomorph assemblage, including the monosaccate pollen grain Cristianisporites triangulatus, provides further evidence of a late Anisian age. An integrated study of fossil assemblages and sedimentary facies reveals tidal and very shallowmarine environments that characterize an extensive epicontinental platform in the western Tethys along the paleo-margin of the Iberian Massif. Two thin shale intervals represent two distinct transgressive phases, correlative to the Pelsonian maximum-flooding zone recorded in other European basins. The new findings contribute to the ongoing paleogeographic reconstruction of epicontinental platform settings which developed during the
Middle Triassic in the Peri-Tethyan realm.