Controls on carbonate deposition and microbialite formation in distal alluvial systems (Campanian, Montalbán subbasin, NE Spain)
The middle-upper Campanian Allueva Formation is located in the continental Montalbán subbasin (NE Spain) at the onset of the Alpine compression. This formation consists of alluvial terrigenous sediments, but it is locally dominated by carbonates and microbialites, which are the main focus of this st...
| Autores: | , , , |
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| Tipo de documento: | artigo |
| Data de publicação: | 2024 |
| País: | España |
| Recursos: | Universitat Autònoma de Barcelona |
| Repositório: | Dipòsit Digital de Documents de la UAB |
| Idioma: | inglês |
| OAI Identifier: | oai:ddd.uab.cat:304733 |
| Acesso em linha: | https://ddd.uab.cat/record/304733 https://dx.doi.org/urn:doi:10.1344/GeologicaActa2024.22.13 |
| Access Level: | Acceso aberto |
| Palavra-chave: | Microbialite Oncoid Upper cretaceous Iberian basin Alluvial |
| Resumo: | The middle-upper Campanian Allueva Formation is located in the continental Montalbán subbasin (NE Spain) at the onset of the Alpine compression. This formation consists of alluvial terrigenous sediments, but it is locally dominated by carbonates and microbialites, which are the main focus of this study. Three facies associations are differentiated: (1) carbonate facies association including limestone levels with bioclastic accumulation of gastropods and charophytes, along with polygenetic carbonate breccias; (2) microbialite facies association including irregular limestone beds rich in oncoids; (3) terrigenous facies association including reddish mudstone m-thick levels with intercalations of sandstones and conglomerates. A lacustrine-palustrine environment was developed in the distal areas of an alluvial setting, which was characterized by low water level and short residence times. Isotopic data shows mean values of -4.95‰ for both δ18O and δ13C, in the range of freshwater carbonates, supporting the proposed interpretation. Cathodoluminiscence analysis allowed the differentiation of three cement phases that suggest the evolution from vadose to phreatic conditions. The most common microbialites are found in form of oncoids forming oncolitic beds. Based on morphology, size and lamination, six different types of oncoids have been described. Furthermore, study of the lamination patterns has been carried out on the oncoids, identifying lamination cycles than can serve as tools for the interpretation of humid/dry conditions. Finally, controls on the formation of the system have been discussed, suggesting the development of a long-distance alluvial setting mainly sourced by meteoric waters and with a sub-humid climate progressively changing to more arid conditions. |
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