Research paper
Ichnological analysis at the Fonte Coberta section (Lusitanian Basin, Portugal): Approaching depositional environment during the Toarcian oceanic anoxic event (T-OAE)
OLMO MIGUEZ-SALAS
Departamento de Estratigrafía y Paleontología, Facultad de Ciencias, Fuentenueva s/n Universidad de Granada, 18002 Granada, Spain. olmoms@ugr.es
Corresponding author
FRANCISCO J. RODRÍGUEZ-TOVAR
Departamento de Estratigrafía y Paleontología, Facultad de Ciencias, Fuentenueva s/n Universidad de Granada, 18002 Granada, Spain. fjrtovar@ugr.es
LUIS V. DUARTE
MARE, Departamento de Ciências da Terra, Sílvio Lima s/n Universidade de Coimbra, Polo II, 3030-790 Coimbra, Portugal. lduarte@dct.uc.pt
ABSTRACT
The Toarcian Oceanic Anoxic Event (T-OAE) is commonly related with an extended marine mass extinction and global oceanic anoxic conditions. However, recently it has been demonstrated that local palaeotopography/palaeogeography can determinate the absence of anoxic conditions, being other limiting environmental parameters of higher significance. The detailed study of the Fonte Coberta section (Lusitanian Basin, Portugal) shows significant changes in the microbenthic community at the lower Toarcian (Levisoni Zone) sediments during the event. In the study section, this interval presents a high degree of bioturbation with a relatively abundant and moderately diverse trace fossil assemblage dominated by Thalassinoides, with punctual Spongeliomorpha. The ichnotaxonomical study conducted on this trace fossil assemblage has allowed the recognition of a single species of Thalassinoides, T. suevicus Rieth, with two different morphotypes (I and II), as well the differentiation of Spongeliomorpha aff. iberica Saporta. The distribution of these ichnospecies, including the diff erentiated morphogroups, along the studied interval, corresponding to the T-OAE, allows refining depositional conditions as changes in the substrate consistency related to variations in relative sea level. Ichnological analysis reveals as a proxy to improve sequence stratigraphy characterization for the Lusitanian Basin during the T-OAE.
Key words: Trace fossils, Thalassinoides suevicus, T-OAE, sequence stratigraphy, Portugal.
How to cite: Miguez-Salas, O., Rodríguez-Tovar, F.J. & Duarte, L.V. 2018. Ichnological analysis at the Fonte Coberta section (Lusitanian Basin, Portugal): Approaching depositional environment during the Toarcian oceanic anoxic event (T-OAE). Spanish Journal of Palaeontology, 33 (2), 261-276.
Received 20 December 2017, Accepted 22 March 2018, Published 31 December 2018
https://doi.org/10.7203/sjp.33.2.13602
