NEOGLOBOQUADRINA ATLANTICA PRAEATLANTICA, NEW SUBSPECIESFROM LATE MIDDLE MIOCENE

A new subspecies of Neogloboquadrina atlantica atlantica previously reported under different names, is here distinguished and named Neogloboquadrina atlantica praeatlantica. Its first occurrence into the Mediterranean dated at 11.78 Ma, is not evolutionary appearance but is related to a global climatic cooling which pushed southwards from high latitude this taxon; however, the area of its evolutionary appearance is not clearly defined; its extinction occurs within the Globigerinoides obliquus extremus Zone. N. atlantica atlantica which evolves from N. atlantica praeatlantica occurs in the Mediterranean at 11.15 Ma, just after the Mediterranean exit of Paragloborotalia siakensis (Le Roy).  &nbsp

ALLOSTRATIGRAPHY AND SEISMIC STRATIGRAPHY OF THE MIOCENE SEDIMENTS OF THE SPICCHIAIOLA - POMARANCE AREA, SOUTHERN SIDE OF THE VOLTERRA BASIN (TUSCANY, ITALY)

The objective of this work is to analyze the Miocene depositional units of the southern side of the Volterra Basin (Tuscany, Italy) utilizing outcrop and seismic data and to establish the major events that led to their formation. Four depositional units have been recognized: Unit 1 is characterized by marine sediments of late Serravallian-early Tortonian age; Unit 2 is characterized by fluvio-lacustrine and brackish deposits of late Tortonian-early Messinian age; Unit 3 is characterized by marine deposits of early Messinian age; Unit 4 is characterized by the lacustrine deposits ("Lago-mare" facies) of late Messinian age. The deposition of these four units is associated with an extensional tectonic regime that has been active in Tuscany since the late Tortonian. This regime generated half graben type structures in which deposition occurred. The recognized unconformities between the units are mainly related to uplift as a consequence of the extensional tectonic regime.   &nbsp

CALCAREOUS PLANKTON HIGH RESOLUTION BIOSTRATIGRAPHY (FORAMINIFERA AND NANNOFOSSILS) OF THE UPPERMOST LANGHIAN – LOWER SERRAVALLIANRAS IL-PELLEGRIN SECTION (MALTA)

Results of an integrated biostratigraphic (calcareous nannofossils and planktonic foraminifers) study of the uppermost Langhian/lower Serravallian Ras il-Pellegrin section (Fomm ir-Rih Bay – Malta) are presented. This high resolution study allowed us to recognise several useful lower Serravallian bio-events in the Mediterranean and to provide a detailed distribution pattern of the recognised taxa. The astrochronological calibration, reported in a different paper of this volume, provided absolute ages of the bio-events of the studied section. The LO (Last Occurrence) of Globorotalia peripheroronda at 13.39 Ma, the Paragloborotalia partimlabiata FO (First Occurrence) at 12.62 Ma and the Paragloborotalia mayeri FCO (First Common Occurrence) at 12.34 Ma among the planktonic foraminifera, and the Sphenolithus heteromorphus LO at 13.59 Ma, the Cyclicargolithus floridanus LCO (Last Common Occurrence) at 13.39 Ma, the Reticulofenestra pseudoumbilicus FCO at 13.32 Ma, the Calcidiscus macintyrei FO at 12.57 Ma and the Calcidiscus premacintyrei LCO at 12.51 Ma among the calcareous nannofossils, were recorded. Moreover, our results confirm the LO of S. heteromorphus as a fairly synchronous event in the Mediterranean and in the Atlantic and Pacific Oceans. Therefore, we suggest a lithological level near or coincident with this event for the definition of the GSSP of the Serravallian. The Ras il-Pellegrin section may be considered a good candidate for this definition.&nbsp

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 Lèuca 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

CALCAREOUS PLANKTON BIO-EVENTS IN THE MIOCENECASE PELACANI SECTION (SOUTH-EASTERN SICILY, ITALY)

The upper Serravallian-Lower Tortonian Case Pelacani section in Sicily is represented by the epipelagic sediments of the Tellaro Formation. Along the section, which was sampled in four easily correlatable segments, a more or less continuous sequence of lithologic couplets, with whitish marls and blackish levels in the lower part and whitish marls and whitish more indurated levels in the upper part are present. The distribution of the most common taxa of planktonic foraminifera and calcareous nannofossils was quantitatively estimated in 316 samples, collected every 20 cm along the section which is 66.35 m thick. This allowed to identify eleven planktonic foraminifera (but only the eight marker events were quantitatively estimated) and five calcareous nannofossil bio-events.  Their astrochronology is reported by correlation with the cyclostratigraphic results obtained for this section in a different paper. The ages are well comparable with the ages published for the same events in other Mediterranean sections. Paleomagnetic analysis along 30 meters in the central part of the section gave puzzling results and therefore no reliable magnetostratigraphy could be obtained. The Case Pelacani section, straddling the stratigraphic interval between slightly below the first occurrence and slightly above the first regular occurrence of Neogloboquadrina acostaensis , is a good candidate for the definition of the GSSP (Global Stratigraphic Section and Point) of the Tortonian. Independently from the selected section, we suggest to define the Serravallian/Tortonian boundary in a level coincident or near the last occurrence of Paragloborotalia siakensis, as already proposed, or coincident with or near the last common occurrence of Globigerinoides subquadratus. This latter level virtually coincides with the first common occurrence of Globigerinoides obliquus obliquus and is slightly above the last common occurrence of Discoaster kugleri, which occurs only 2.25 meters (and 3 precessional cycles) below in the studied section.&nbsp

AN INTEGRATED CALCAREOUS PLANKTON BIOSTRATIGRAPHIC SCHEME AND BIOCHRONOLOGY FOR THE MEDITERRANEAN MIDDLE MIOCENE

The relative position of 30 main bioevents  pertaining to calcareous nannofossils and planktonic foraminifera was identified in the time interval between 13.75 Ma and 10.50 Ma, based on the quantitative study of the those microfossils in three Mediterranean sections spanning the late Langhian – lower Tortonian stratigraphic interval. The events were correlated  to the astronomic target curve using a cyclostratigraphic approach, resulting in a very detailed biostratigraphic and biochronologic subdivision of the interval. The zonal scheme proposed by Fornaciari et al. (1996) was adopted for the calcareous nannofossils, but three subzones were identified in the MMN7 Zone. For the planktonic foraminifera reference is made to the zonal scheme recently proposed by Foresi et al. (1998), slightly modified in order to increase its biostratigraphic resolution. The age of all the zonal boundaries is reported.&nbsp

ASTROCHRONOLOGICAL CALIBRATION OF THE UPPER SERRAVALLIAN/LOWER TORTONIAN SEDIMENTARY SEQUENCE AT TREMITI ISLANDS(ADRIATIC SEA, SOUTHERN ITALY)

A high resolution cyclostratigraphic study was carried out on a cyclicaly bedded succession of late Middle Miocene deep marine deposits from the Tremiti Islands, Adriatic sea (Italy). Astronomical calibration of the sedimentary cycles provides absolute ages for different calcareous plankton bioevents, widely used for intra Mediterranean correlation, in the interval between 11.12 and 12.60 Ma. The sedimentary record of the S. nicola composite section consists of an alternation of indurated, withish coloured, CaCo3 rich and grey less indurated, CaCo3 poor marly beds, at times replaced by red coloured CaCo3 poor marls. Results of direct correlation between the La 90 (1,1) solution of the insolation curve and the cyclic lithologic patterns occurring in the studied sections, combined with results of spectral methodologies applied on the climate sensitive data (CaCo3 and Globigerinoides) showed that the classic Milankovitch periodicity can be represented through the modulation forcing of the studied sedimentary records.&nbsp

HIGH RESOLUTION CALCAREOUS PLANKTON BIOSTRATIGRAPHY OF THE SERRAVALLIAN SUCCESSION OF THE TREMITI ISLANDS (ADRIATIC SEA, ITALY)

The planktonic foraminifer and calcareous nannofossil content of two Middle Miocene sections of the Tremiti Islands (Southern Adriatic Sea) have been studied. The two sections are composed of marly limestones rich in calcareous plankton which show cyclic alternations of indurated (higher carbonate content) whitish and less indurated grey or reddish beds. The two sections represent a succession with a total thickness of 38 m. Samples have been collected at a mean spacing of 10-15 cm; qualitative analyses were performed on one sample per meter but quantitative analyses were made for each sample. The abundance fluctuations of several marker species proved to be a very useful tool to correlate the two sections. The astronomical calibration of the sedimentary cycles provided absolute ages for all the recognised calcareous plankton bioevents.&nbsp

Neogloboquadrina atlantica praeatlantica, new subspecies from late Middle Miocene

3noreservedA new subspecies of Neogloquadrina atlantica atlantica previously reported under different names, is here distinguished and named Neogloboquadrina atlantica praeatlantica. Its first occurrence into the Mediterranean dated at 11.78 Ma, is not evolutionary appearance but is related to a global climatic cooling which pushed southwards from high latitude this taxon; however, the area of its evolutionary appearance is not clearly defined; its extinction occurs within the Globigerinoides obliquus extremus Zone. N. atlantica atlantica which evolves from N. atlantica praeatlantica occurs in the Mediterranean at 11.15 Ma, just after the Mediterranean exit of Paragloborotalia siakensis (Le Roy).mixedFORESI, L.M.; IACCARINO, S., SALVATORINI, G.Foresi, L. M.; Iaccarino, S.; Salvatorini, G

NEW DATA ON MIDDLE TO LATE MIOCENE CALCAREOUS PLANKTON BIOSTRATIGRAPHY IN THE MEDITERRANEAN AREA

Planktonic foraminifera from one Atlantic Ocean (Site 397) and five Mediterranean sequences of middle to late Miocene age were investigated. The aim of the research was to refine the biostratigraphy of the Serravallian to early Tortonian interval and, since the recent literature provides no general consensus, to check the range of Neogloboquadrina acostaensis (Blow) and Paragloborotalia siakensis (Le Roy). Examination of planktonic foraminifera identified a succession of events which is, in part, new in the Mediterranean area, and documented an overlap in the distribution of N. acostaensis and P.lia siakensis. Based on the new data, the zonal scheme for the Serravallian to early Tortonian interval proposed by Iaccarino and Salvatorini (1982) and Iaccarino (1985) was emended. In particular, it was ascertained that the first occurrence (FO) of N. acostaensis falls in the upper part of the Serravallian, well before the last occurrence (LO) of P.lia siakensis. The new zonation was calibrated with the calcareous nannofossil zonation and the geomagnetic polarity time scale. In light of these new data, the events closest to the base of the Rio Castellania-Rio Mazzapiedi-Tortonian type-section are interpreted to be the LO of P.lia siakensis, the first common occurrence (FCO) of N. acostaensis, and the FO of Discoaster hamatus.. Therefore, the use of these events in selecting the GSSP of the Serravalian/Tortonian boundary is recommended.&nbsp