Fossildiagenesis of the annelid Rotularia spirulea (Lamarck, 1818) (Polychaeta, Serpulidae) from the Eocene of the western Pyrenees
Departamento de Mineralogía y Petrología, Facultad de Ciencia y Tecnología, Universidad del País Vasco/Euskal Herriko Unibertsitatea (UPV/EHU), Apartado de correos 644, 48080 Bilbao. firstname.lastname@example.org
Departamento de Estratigrafía y Paleontología, Facultad de Ciencia y Tecnología, Universidad del País Vasco/Euskal Herriko Unibertsitatea (UPV/EHU), Apartado de correos 644, 48080 Bilbao. email@example.com
The presence of the fossil polychaete Rotularia spirulaea (Lamarck, 1818) in Eocene deposits (middle Lutecian – upper Bartonian and (?) Priabonian) belonging to the western Pyrenean Domain is verified. In this paper, a fossildiagenetic study has been carried out. Fossils from three areas, corresponding to different depositional settings, have been analysed. In area 1, sediments of the Ardanatz Sandstone and Ilundain Marls formations [Pamplona Basin and adjoining areas (Navarre)], were sampled. Here, the specimens of R. spirulaea were not substantially affected by taphonomic reworking and the original microstructure of the carbonate tube is preserved. The test consists of a thick external Shell layer, composed of three zones in succession, and another extremely thin inner shell layer. The lumen of the tube is filled in by fine-grained sediment and/or calcitic cement. In area 2, which includes the town of Anderatz and several outcrops of the Urbasa mountain range (Navarre), Urbasa-Andia Formation and overlying deposits, as well as in area 3, located on the upper part of the calciclastic flysch of Punta Galea (Biscay), fossils are included in sediments deposited in high-energy environments. In this case, the microstructure of R. spirulaea tube is not completely recognized due to intense, early diagenetic silicification affecting the tests. The lumen is filled in with fragments of foraminifera and calcareous algae, quartz-feldespathic sediment and cemented by calcite. Therefore, in zones 2 and 3 the fossildiagenetic processes are substantially different from those recognized in zone 1. In this paper, the differential preservation of the microstructure depending upon the study areas is described and the diagenetic mechanisms behind these processes are discussed.
Key words: Rotularia spirulaea, morphology, fossildiagenesis, Paleogene, Pyrenees.
How to cite: Elorza, J. & Astibia, H. 2018. Fosildiagénesis del anélido Rotularia spirulaea (Lamarck, 1818) (Polychaeta, Serpulidae) en el Eoceno del dominio pirenaico occidental. [Fossildiagenesis of the annelid Rotularia spirulea (Lamarck, 1818) (Polychaeta, Serpulidae) from the Eocene of the western Pyrenees]. Spanish Journal of Palaeontology, 33 (2), 299-320.
Received 25 July 2018, Accepted 1 October 2018, Published 31 December 2018