A Bossio

The Eocene/Oligocene boundary and the psychrospheric event in the Tethys as recorded by deep-sea ostracods from the Massignano Global Boundary Stratotype Section and Point, Central Italy

Abstract Latest Eocene–earliest Oligocene deep water ostracods from the Massignano Global Boundary Stratotype Section and Point (GSSP), Central Italy, were studied from a palaeoecological perspective to investigate the psychrospheric event in the Tethys. Although quantitative analyses were hampered by the low incidence of fauna, the high-resolution sampling used in this study (148 samples distributed over a 23-m-thick succession spanning 3 m.y.) allowed the following inferences: (1) overall features (e.g. abundance, diversity, composition) of the assemblages suggest a middle–lower bathyal environment with no significant palaeobathymetrical changes; (2) today a similar fauna, notably characterised by the common occurrence of the genus Agrenocythere, would likely be encountered in upper psychrospheric conditions (water masses beneath the permanent thermocline with a temperature range of 4–10°C); (3) although no noticeable faunal turnover has been recognised throughout the succession, minor faunal changes seem to occur in the first part of the section (probable appearance of Legitimocythere presequenta) and to a lesser extent also across the Eocene/Oligocene boundary. The presumed appearance of L. presequenta (latest Eocene) correlates quite well in timing and possible significance with the faunal changes observed in other microfossil groups (foraminifers and dinocysts). This event is possibly linked to a cooling pulse, which might have been caused by the arrival, or increasing advection, of cold bottom waters in the study area. Faunal evolution across the Eocene/Oligocene boundary is thought to be consistent with an intensification of the cooling trend and an increase of primary productivity, which fits fairly well with the δ13C record. Relationships between the subtle ostracod faunal changes observed in the Massignano GSSP and the main Late Eocene–Early Oligocene psychrospheric event can be only speculative. Nevertheless, we found no evidence that precludes the possibility of interpreting the Massignano ostracod pattern as a subdued, local expression of this major event. Although speculative, this is a reasonable hypothesis, because the investigated area is situated in Western Tethys, far from the main circulation of deep ocean waters.

NOTE GEOLOGICHE E STRATIGRAFICHE SULL'AREA DI PALMARIGGI (LECCE, PUGLIA)

The geological mapping and the biostratigraphic study of Neogene sediments outcropping near Palmariggi, a small area between Otranto and Maglie (Puglia), have been carried out. Above the dolomitic limestone units of the Cretaceous-Oligocene platform three sedimentary cycles have been recognized, one of Miocene and two of Pliocene age. The first cycle consists of two units: the Pietra leccese and the overlying Calcareniti di Andrano; the second cycle is represented by the Leuca Formation and the last cycle by the Uggiano la Chiesa Formation. The pre-Neogene units are affected by a folding episode with major structures trending NNW- SSE. A subsequent tectonic event characterized by folds with axial directions interferring with the previous one has been detected in the pre-Neogene units. The latter deformation affects also the Miocene successions. Both the previous deformative episodes control the outcrop distribution of the Neogene sediments, preserved in the low structural sites such as synclinal cores. In the Palmariggi area an extensional tectonics of pre-Pliocene age follows the folding related to the compressive episodes. The normal faults linked to this late extension, show a NNW-SSE trend.

The Miocene of Pianosa Island: key to understanding the opening of the Northern Tyrrhenian back-arc basin (Central Mediterranean)

The only place where Neogene–Quaternary rocks crop out for the entire Tuscan Archipelago in the Northern Tyrrhenian Sea is the island of Pianosa. In particular, the Miocene deposits record the depositional and tectonic evolution of the Northern Tyrrhenian region during this time period. These deposits are subdivided into two successions separated by a low-angle unconformity. The older, middle Burdigalian succession represents a calciturbidite shallow marine system, whereas the younger late Tortonian–early Messinian succession comprises a continental alluvial system that evolves upwards into a lagoonal–marginal marine environment. Here we present sedimentological, palaeontological and petrographical data that support a new stratigraphic and palaeogeographical framework for reconstructing the opening of the Northern Tyrrhenian back-arc basin. The early Miocene succession records a pre-rift marine depositional phase followed by a late Burdigalian–Langhian erosional phase. This was followed by a period of synrift continental-marginal deposition, as recorded by the late Miocene succession, terminated by an important phase of uplift, probably induced by the start of magmatic activity in the Tuscan Archipelago area.

MIDDLE MIOCENE OSTRACODS FROM THE SALENTINE PENINSULA

The ostracod faunas of the S. Caterina and S. Maria al Bagno sections (Salentine Peninsula, Apulia) were studied. These sections comprise the lower and middle levels of the Pietra Leccese formationand range collectively from the uppermost Burdigalian or the lower Langhian to the middle Serravallian. Forty-one species, belonging to twenty-seven genera were identified. Nineteen species known previously are illustrated and discussed; six ( Carinocythereis messapica n. sp., Celtia multicostata n. sp., Cytherella obesa n. sp., Cytherella polygonalis n. sp., Cytherella salentinensis n. sp. and Cytherelloidea ? rectangularis n. sp.) are described as new, and two are left in open nomenclature. The stratigraphic distribution of a remarkable number ofshelf ostracod species,known previously from the Upper Miocene upwards, includes also part of the Middle Miocene.

Unusual Debris Flow Deposits from the Base of the Malta Escarpment (Eastern Mediterranean)

The more than 3000 m high Malta Escarpment forms the western boundary of the eastern Mediterranean. The escarpment has an average dip of about 20°, however the lower part of the escarpment is steeper and has a slope of approximately 60° (Figure 1). Extensive exposures of late Triassic-lower Liassic shallow water limestone occurs along this lower part of the escarpment (Chayes et al, 1980; Scandone et al, in press; Cita et al, in press).