Increasing size and abundance of microbialites (oncoids) in connection with the K/T boundary in non-marine environments in the South Central Pyrenees

Authors

  • H. ASTIBIA Departamento de estratigrafía y Paleontología, Facultad de Ciencia y Tecnología, Universidad del País Vasco/euskal Herriko Unibertsitatea. Apartado correos 644, 48080 Bilbao.
  • N. LÓPEZ-MARTÍNEZ Departamento de Paleontología, Facultad de Ciencias Geológicas, Universidad Complutense de Madrid. José Antonio Novais, 12, Ciudad Universitaria, 28040 Madrid.
  • J.J. ELORZA Departamento de Mineralogía y Petrología, Facultad de Ciencia y Tecnología, Universidad del País Vasco/euskal Herriko Unibertsitatea. Apartado correos 644, 48080 Bilbao.
  • E. VICENS Departament de Geologia, Facultat de Ciències, Universitat Autònoma de barcelona (UAB). Campus Universitari UAB, 08193 Bellaterra (Cerdanyola del Vallès).

Keywords:

K/T boundary, Oncoids, Non-marine environments, South Pyrenean basin

Abstract

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 δ13C 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.

Downloads

Issue

Vol. 10 No. 3 (2012)

Section

Articles

License

Copyright

The commercial rights of the printed and online versions of Geologica Acta are property of the UB, ICTJA, IDAEA and UAB, and Geologica Acta must be cited for any partial or full reproduction.

The opinions and conclusions stated in each article are the exclusive responsability of the authors and do not necessarily coincide with those of the above mentioned institutions UB, ICTJA, IDAEA and UAB.

Author Rights

Authors retain the copyright on their papers (accepted manuscript, uncorrected proof and published paper) and are authorized to post them on their own Web page or their institutional repositories. In all cases, the complete citation and a link to the Digital Object Identifier (DOI) of the article must be included.

The authors can use excerpts or reproduce illustrations of their papers in other works without prior permission of Geologica Acta provided the source of the paper including the complete citation is fully acknowledged.

Papers are distributed under the Attribution-Share Alike Creative Commons License. This license allows others to alter, remix or build upon a paper and the resulting work may be distributed under the same or similar license to this one.