Upper Oligocene (Chattian) brachiopod fauna from the Aquitaine Basin, southwestern France and its paleoenvironmental implications

Abstract

Brachiopods from the Upper Oligocene (Chattian), Aquitaine Basin, southwestern France comprise nine species in seven genera: Novocrania Lee & Brunton, 2001, Terebratulina d'Orbigny, 1847, Megathiris d'Orbigny, 1847, Argyrotheca Dall, 1900, Joania Álvarez, Brunton & Long, 2008, Megerlia King, 1850, and Lacazella Munier-Chalmas, 1880. One megathyridid is described as a new species, Joania peyrerensis n. sp., characterized by ornamentation of 6–8 distinct, sharp ribs and by triangular, plate-like teeth. With the exception of Megathiris detruncata (Gmelin, 1791) and Lacazella mediterranea (Risso, 1826), all species are recorded for the first time from the Oligocene of the Aquitaine Basin. In taxonomic composition this brachiopod fauna displays close affinity with the Miocene faunas of the Mediterranean Province and Central Paratethys. The dominance of micromorphic megathyridids and thecideides in the Peyrère assemblage, characteristic of cryptic habitats suggests the presence of submarine caves and/or crevices, thus supporting the previous interpretations of this faunistic assemblage as a cave biocenosis. Frequency of gastropod drillings observed on the investigated brachiopods is low (4%) as is in most Cenozoic brachiopod populations. The paleotemperatures calculated from the δ18O values of brachiopod shells (21 to 24°C) correspond well to a paleoenvironmental interpretation based on paleoecology of other taxonomic groups.