BRYOZOANS AND MICROMORPHIC BRACHIOPODS (LOPHOPHORATA) FROM THE BARTONIAN-PRIABONIAN OF THE ALANO DI PIAVE SECTION (NE ITALY)

The Alano di Piave section (Veneto region, NE Italy) contains one of the best Tethyan hemipelagic records of the Middle-Late Eocene transition and has been recently proposed as candidate for the Global Stratotype Section and Point (GSSP) of the Priabonian (Agnini et al., 2011). It consists of ~130m of mid bathyal marls with intercalated several silty-sandy and ruditic layers of variable thickness and composition. During micropaleontological investigations, several specimens of bryozoans and brachiopods have been recovered, mostly in correspondence of two bioclastic beds located at +19 and +32m within the Bartonian portion of the section. Such beds include larger foraminifera (nummulitids and orthophragminids) and other bioclasts whose source area was the nearby Lessinian Shelf. Bryozoans commonly occur, but their moderate to poor preservation state often hampers confident taxonomic identification. The bryofaunal composition is identical in both the beds and arborescent cyclostomes dominate in abundance over cheilostomes. Cyclostomes and cheilostomes belong to erect rigid and flexible growth forms, indicating a source area in a quiet environment at about 150-200m of depths. The presence of the encrusting species Vibracella trapezoidea is compatible with such environment, because it frequently encrusted on nummulitids. The Bartonian assemblage from Alano, on the whole, is very similar to the rich Priabonian-Rupelian bryofaunas of the classical shallow-water sections of the Berici Hills and Lessini Mts., West of Alano di Piave (e.g. Braga, 2008). The brachiopod fauna, mostly recovered from the upper bioclastic bed ("Canova bed", at +32m) consists of six, exclusively micromorphic, species belonging to five genera, i.e. Terebratulina tenuistriata, Orthothyris pectinoides, Lacazella mediterranea, Joania cf. cordata, Argyrotheca cf. cuneata, and Argyrotheca sp. cf. A. crassicostata. The former three species have been already reported from the Late Eocene of NE Italy (Bitner & Dieni, 2005) and are widely distributed throughout whole Europe. The occurrence in the studied assemblage of Joania extends the stratigraphical range of this genus from the Oligocene to the Middle Eocene (Bartonian). Within the Priabonian portion of the Alano section, from ca. +100m upward, a bispecific, low-density bryozoan assemblage (Batopora rosula + B. stoliczkai) is present. The absence of bioclastic beds or other sedimentary disturbances indicate a genuine, in situ assemblage. Based on benthic foraminiferal assemblages and Recent monospecific or oligospecific assemblages of conescharelliniform (e.g. Moissette 1996), we interpret such Batopora assemblage as characteristic of soft sediments deposited in a full bathyal environment. Such finding probably represents the first record of a deep-water conescharelliniform assemblage in the Eocene of Italy.