Taphonomic analysis of the Rosario Mine (Valdeteja Formation, Bashkirian, NW Spain): evidence of tsunamis or cyclones

ABSTRACT

This study presents the analysis of the taphonomical processes at the Rosario Mine (Valdeteja Formation, León). The studied beds are an ensemble of normal graded sequences comprised of rudstones and grainstones that pass upwards to packstones and finally to marls. The last sequence culminates in a 3 m thick bed of carbonaceous shales with coal balls. In the limestones there are evidences of breakage, resedimentation and even some reworking. The top of the packstones and the marls show hummocky cross stratification and abundant burrows. The fossils in the limestones represent an allochthonous assemblage, while the marls contain a mostly autochthonous assemblage, typical of a deep marine environment.These sequences were deposited in a deep area of a tropical carbonate platform in a foreland basin, and they resulted from mass flows triggered by large waves followed by quiet background environmental conditions. Tsunamis or cyclones could be the events originating these sequences. The characteristic of the deposit and the palaeogeographical framework have been examined to try to differentiate between these events. The climate and tectonic context during the sedimentation support both possibilities, while the deep environment and the amount of plant remains dragged to the sea seem more consistent with tsunamis.

KEYWORDS:

• Cantabrian mountains
• león
• coal balls
• hummocky cross stratification

Acknowledgments

We thank Nasrollah Abbassi and an anonymous reviewer for their contributions to the text. We are also thankful for the grammar check by Paloma Ninde.

This research was funded by the Research project CGL2016-78738-P of the Spanish Ministry of Research and Innovation. The research of I. R-C is funded with the grant FPU 18/03207 of the Spanish Ministry of Universities. The thin sections were done by Esther Navarro.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Ministerio de Universidades [FPU 18/03207]; Ministerio de Economía y Competitividad [CGL2016-78738-P].