CHONDRITES-CLADICHNUS ICHNOCOENOSIS FROM THE DEEP-SEA DEPOSITS OF PIERFRANCESCO (CRETACEOUS; ITALY): OXYGEN- OR NUTRIENT-LIMITED?

The Italian Northern Apennines are acknowledged as the place where ichnology was born, but there is comparatively little work about their ichnological record. This study bridges this gap by describing two new ichnosites from the locality of Pierfrancesco, which preserve an abundant, low-disparity trace-fossil assemblage within the Late Cretaceous beds of the M. Cassio Flysch. Results show that lithofacies and ichnotaxa are rhythmically organized. The base of each cycle consists of Megagrapton-bearing calciclastic turbidites, which are overlain by marlstone beds with an abundant, low-disparity assemblage of trace fossils. This includes Chondrites intricatus, C. patulus, C. targionii, C. recurvus and Cladichnus fischeri. The cycle top consists of mudstones with no distinct burrows. The rhythmic pattern of Pierfrancesco reflects a deep-sea ecological succession, in which species and behaviour changed as turbidite-related disturbances altered the seafloor. This study opens the question of whether the Chondrites-Cladichnus ichnocoenosis represents low-oxygen or nutrient-poor settings.

Early Miocene stalked crinoids (Echinodermata) from the southern Rhodanian basin (southeastern France). Paleoenvironments and taxonomy

Using recent samplings and specimens from ancient collections, 14 sites and five species of stalked crinoids have been listed in the Miocene of the southern Rhodanian basin (southeastern France). Three species and two genera are new for science: Papacrinus avignonensis n. gen., n sp. (Balanocrininae), Paraconocrinus rhodanicus n. sp. (Rhizocrinidae) and Gastecrinus vinealis n. gen., n. sp. (Incertae sedis). The identification among the Mediterranean Miocene fauna of the genus Metacrinus, now confined to the Indo-Pacific province, was confirmed by the discovery of brachial ossicles attributed to Metacrinus berthei. The richest and most diversified site was exposed during temporal excavations at the Place du Palais des Papes in Avignon. Four out of the five stalked crinoid species were found in this fossil assemblage in which M. berthei predominates. ?Endoxocrinus gastaldii is associated with M. berthei in several sites. Using dissociated ossicles, differences in quantitative and qualitative characters between these two species are deeply analyzed with their taphonomical, taxonomical and paleoecological consequences. Paleoreliefs and valleys, which had been incised during the Burdigalian, channeled currents. They favored stalked crinoid settlement on various substrates during the late Burdigalian—Lower Langhian transgression. Comparison with the extant fauna allows us to estimate the depth range of the biotopes with stalked crinoids from 100 to 250 m. These estimates are in agreement with those deduced from other paleontological studies.