Increasing size and abundance of microbialites (oncoids) in connection with the K/T boundary in non-marine environments in the South Central Pyrenees
Astibia Ayerra, Humberto (Universidad del País Vasco. Departamento de Estratigrafía y Paleontología)
López-Martínez, N. (Universidad Complutense de Madrid. Departamento de Paleontología)
Elorza, J. (Universidad del País Vasco. Departamento de Mineralogía y Petrología)
Vicens, Enric (Universitat Autònoma de Barcelona. Departament de Geologia)

Fecha:	2012
Resumen:	A layer rich in giant microbialites, developed within continental deposits of the Tremp Formation (South-Central Pyrenees) in the aftermath of the end-Cretaceous mass extinctions, is here reported for the first time. Its stratigraphic location just above the Latest Maastrichtian Reptile Sandstone unit, and a characteristic 13C anomaly, are clear proofs linking this so-called "z" layer to the K/T boundary. The great abundance of microbialites, their outsized dimensions (oncoids with coating thickness up to 1. 2m; average >50mm), and the great lateral continuity of the "z" layer in the study zone, support the hypothesis that these giant microbialites may represent disaster forms linked to the latest Mesozoic crisis. To our knowledge, this is the first time a record of this type is reported in continental realms. Other large continental oncoids and stromatolite constructions (e. g. , in the Late Palaeogene deposits of the Pyrenees, Ebro basin, and Mallorca island) differ from those of the "z" layer in occurring in carbonate rocks and in having less lateral continuity, but they could also have been favoured by palaeoenvironmental crises, such as the global Eocene hyperthermals, Early Eocene Climatic Optimum, Middle Eocene Climatic Optimum, and the climatic cooling of the Eocene-Oligocene transition. It is thus possible that some layers of microbialites may record biotic crises in continental series, as they do in the marine record.
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.
Lengua:	Anglès
Documento:	Article ; recerca ; Versió publicada
Materia:	K/T boundary ; Oncoids ; Non-marine environments ; South Pyrenean basin
Publicado en:	Geologica acta, Vol. 10, Núm. 3 (Setembre 2012) , p. 209-226, ISSN 1696-5728

Adreça alternativa: https://raco.cat/index.php/GeologicaActa/article/view/263379
DOI: 10.1344/105.000001670

18 p, 3.6 MB

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