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Coastal salina evaporites of the Triassic-Liassic boundary in the Iberian Peninsula : the Alacón borehole
Ortí Cabo, Federico (Universitat de Barcelona. Departament de Mineralogia, Petrologia i Geologia Aplicada)
Salvany i Duran, Josep Maria (Universitat Politècnica de Catalunya. Departament d'Enginyeria Civil i Ambiental)

Fecha: 2004
Resumen: The evaporite unit (the Lécera Formation), which was formed at the Triassic-Liassic boundary in the Aragonian Branch of the Iberian Chain, was studied at the 01 Alacón borehole (Alacón village, Teruel province), where it is mainly constituted by a thick (>300 m) succession of predominant sulphates (anhydrite, secondary gypsum and carbonate) overlain by brecciated carbonates. In the evaporite succession, a number of lithofacies were recognized, which can be grouped into an "ideal cycle", from base to top: (C1) massive to banded carbonate mudstone, (C2) alternation of carbonate and anhydrite laminae, (A1) alternation of anhydrite and carbonate bands, (A2) clastic intercalations in the alternation of anhydrite and carbonate bands, (A3) laminated to banded anhydrite, (A4) bedded pseudomorphs, (A5) interstitial pseudomorphs, and (A6) massive to nodular anhydrite. Fine-grained gypsum (anhydrite laminae and bands), bedded selenitic gypsum (bedded pseudomorphs), interstitial selenitic gypsum (interstitial pseudomorphs), and graded-nodular anhydrite (a particular fabric of nodular anhydrite) were the most outstanding depositional lithofacies. The evaporite succession exhibits a marked cyclicity: in the lower part the individual cycles are more similar to the ideal cycle and reflect deeper water settings, whereas in the upper part they correspond to shallower water settings. The evaporite sedimentation mainly occurred in a subsiding coastal basin of the salina or lagoon type. In this setting, the subaqueous precipitation of the carbonate and gypsum lithofacies was followed, in each cycle, by the interstitial growth of anhydrite in exposed conditions. As a whole, the evaporite succession reflects an infilling process. The conversion into anhydrite of the selenitic gypsum -probably also of the rest of depositional gypsum lithofaciesstarted under synsedimentary conditions and followed during shallow to moderate burial diagenesis.
Derechos: Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, la comunicació pública de l'obra i la creació d'obres derivades, fins i tot amb finalitats comercials, sempre i quan aquestes es distribueixin sota la mateixa llicència que regula l'obra original i es reconegui l'autoria de l'obra original. Creative Commons
Lengua: Anglès
Documento: article ; recerca ; publishedVersion
Materia: Evaporites ; Anhydrite ; Salina ; Triassic-Liassic boundary ; Iberian Chain
Publicado en: Geologica acta, Vol. 2, Núm. 4 (2004) , p. 291-304, ISSN 1696-5728

Adreça alternativa: https://www.raco.cat/index.php/GeologicaActa/article/view/82210
DOI: 10.1344/105.000001421


14 p, 1.2 MB

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