Occurrence of roveacrinoidal assemblages (Roveacrinida, Crinoidea) in the Upper Cretaceous carbonate microfacies of Portugal

Abstract

Roveacrinoids are a group of small, stemless, pelagic crinoids that are widespread in the Cretaceous carbonate microfacies of the fully-marine environments of the Tethysian Realm. Th eir minute remains have been described from a variety of outer shelf assemblages from Brazil, North and West Africa, and Europe, including Spain, where they can be quite abundant in high sea-level successions of platform carbonates. Despite their wide geographical dispersal and rather broad stratigraphic range, the occurrence of the family Roveacrinidae in the Cretaceous marine series of mainland Portugal had been so far lacking confi rmation. A detailed study of carbonate microfacies has been purportedly undertaken in the Upper Cenomanian limestone units of Figueira da Foz (Costa d’Arnes Formation), where the most representative, microfossil-rich, outer shelf carbonate facies from the northern sector of the West Portuguese Carbonate Platform are exposed. Th e research thesaurus comprised four local stratigraphic sections showing a succession nearly 30 metres-thick, with massive limestone and marly limestone beds designated as units “C” to “J”. Th ese Tethysian carbonates were sampled through a collection of 85 thin sections, all representative of the diff erent facies and stratigraphic levels. Th e subsequent microfacial analysis evidenced several roveacrinid taxa in carbonate levels rich in dasycladacean algae, planktonic and benthonic foraminifers, as well as diverse invertebrate microremains, including sponges, bryozoans, bivalves, gastropods, serpulids, and echinoids. Th e assemblages consist of Roveacrinus geinitzi, Roveacrinus cf. alatus, Roveacrinus communis, and Roveacrinus sp., suggesting the presence of an outer shelf, rather deep water environment, able to support a diverse benthonic fauna, together with planktonic and nektonic elements. Figueira da Foz, Portugal