Rodolfo Sprovieri

A high-resolution record of the last deglaciation in the Sicily Channel based on foraminifera and calcareous nannofossil quantitative distribution

Abstract Relative abundance fluctuations in planktic foraminiferal and calcareous nannofossil assemblages are reported on the basis of a high-resolution study of ODP Leg 160 Hole 963D, drilled in the Sicily Strait, near Capo Rossello (southern Sicily). With its 8 m of undisturbed sediments, the core covers the interval from 1.5 to 23 kyr, allowing a 50–100-yr sampling resolution. All the short warm and cold events and sub-events recorded in this time interval in the GRIP Greenland ice core and at several Mediterranean sites were recognized. On this basis, a total number of nine ecozones based on planktic foraminifera and seven ecozones based on calcareous nannofossils were identified. A short interval of climatic amelioration, identified above the base of the Holocene, precedes the segment contemporaneous with the deposition of sapropel S1, which has no lithological expression in the local sedimentary record. This segment has been subdivided into the two warm S1a and S1b phases, separated by a cold intermediate event. A gradual climatic deterioration is recorded above the top of the interval correlated with sapropel S1. It is interrupted by short cold spells, tentatively correlated with similar short duration cold events reported for this interval in the recent literature.

Sedimentary, stable isotope and micropaleontological records of paleoceanographic change in the Messinian Tripoli Formation (Sicily, Italy)

Abstract The Tripoli Formation (6.96–5.98 Ma) of the Central Sicilian Basin provides a good record of the paleoceanographical changes that affected the Mediterranean during the transition from slightly restricted conditions to the onset of the Messinian Salinity Crisis. The Falconara/Gibliscemi section has been selected for an integrated approach at a high resolution scale using sedimentology, stable isotopes of the carbonates and microfossils. The sedimentary succession includes 46 precession-controlled cycles resulting from the periodical increase in biosiliceous productivity (diatomites) that followed the deposition of marls and pinkish laminites, which appear as sapropel-type deposits induced by the oceanic fertilization by terrestrial nutrients during wet periods. Higher scale environmental changes are superimposed to this precession forced rhythmicity. There is a general trend of increasing basin restriction from near marine conditions at the base of the Tripoli to semi-closed settings in its uppermost part, which are the prelude of the salinity crisis. This pattern reflects the hydrological response of the Mediterranean to the progressive decrease of the Atlantic inputs and an enhanced influence of the climate on depositional conditions. However, this evolution is not linear and shows successive phases of different duration. During the first period (until 6.71 Ma), open Atlantic–Mediterranean exchanges maintained relatively stable marine conditions. The second period (6.71–6.29 Ma), marks an important step in the basin restriction with a wider range of salinity fluctuations and an increased bottom stagnation. The 6.71-Ma event, which is correlated at a Mediterranean scale, may have resulted from shallowing of the Mediterranean gateway under a tectonic control. This shallowing reduced the oceanic inputs resulting in an increased climatic constraint of the Mediterranean hydrology. During the third period (6.29–6.03 Ma) an increase of the surface water salinity resulted in stressful conditions for the marine microfauna. The 6.29-Ma change is a major step in the restriction that may be correlated with the intensification of the glaciation recorded in the Atlantic, which could have enhanced the effects of the tectonic closure. The last two cycles (48 and 49), that underlie the ‘Calcare di Base’, witnessed the rapid transition to a semi-closed Mediterranean setting characterized by large variations of salinity from diluted to hypersaline conditions, under a dominant climatic control, and by the nearly complete disappearance of the marine organisms. Long-trend environmental changes recognized within the Tripoli Formation resulted from a complex set of interfering factors controlling the water fluxes exchanged between the Mediterranean and the world ocean. Most of the rapid changes identified in Falconara/Gibliscemi at 7.16, 6.71 and 6.29 Ma, that occurred simultaneously in the western and eastern Mediterranean, were mainly controlled by the stepwise tectonic closure of the Atlantic connections, although a glacio-eustatic overprint cannot be completely excluded.

Sedimentary and diagenetic markers of the restriction in a marine basin: the Lorca Basin (SE Spain) during the Messinian

Apparatus for automatically measuring and plotting the force-deflection curve of springs, especially small springs on which forces are to be applied in order of 0.1 to 100 grams.

Calcareous plankton biostratigraphy and biochronology of the Pliocene-Lower Pleistocene succession of the Capo Rossello area, Sicily

Abstract In the first part of this paper we present the calcareous nannofossil biostratigraphy of the Capo Rossello section (Sicily), which suggests that a sedimentary gap exists at the contact between the “Trubi” and the overlying Monte Narbone Formation, close to the top of the proposed Zanclean stratotype. This suggestion is supported by the planktonic foraminiferal results and field observations. In contrast, the transition from the “Trubi” to the Monte Narbone Formation is well exposed, gradational and biostratigraphically continuous in the nearby section of Punta Piccola. A composite of the Capo Rossello and Punta Piccola sections serves as a good biostratigraphic reference for the Pliocene of the Mediterranean. In a second part of this paper, we have attempted to update the Mediterranean Pliocene time framework by integrating all of the available biostratigraphic, biochronologic, chronostratigraphic, paleomagnetic and radiometric data.

Pliocene-lower Pleistocene chronostratigraphy: A re-evaluation of Mediterranean type sections

The Pliocene-Pleistocene stages defined for the Mediterranean region are generally used as the standard chronostratigraphic units for the upper Neogene and Quaternary. The recently developed calcareous plankton bio-chronology based on results from Ocean Drilling Program Leg 107 and numerous outcrop sections provides the necessary time control for evaluating the ages and stratigraphic relationships for the various Pliocene-Pleistocene stages and their associated stratotypes. Our results indicate that the currently accepted stratotypes do not provide a continuous stratigraphic representation for all of Pliocene-early Pleistocene time. On the basis of these findings, we propose a revised chronostratigraphic scheme for this time period. A tripartite subdivision is proposed for the Pliocene Series. The Zanclean Stage is retained for the lower Pliocene, representing the interval from the Miocene/Pliocene boundary (ca. 4.93 Ma) to ca. 3.5 Ma. The middle Pliocene is represented by the Piacenzian Stage, and it incorporates strata deposited from ca. 3.5 to 2.5 Ma. None of the currently used Pliocene stages fully represents the upper Pliocene (ca. 2.5 to 1.6 Ma). As a result, late Pliocene time lacks an adequately defined chronostratigraphic unit. The Selinuntian Stage appears to be the most appropriate stage for the lower Pleistocene (ca. 1.6 to 0.8 Ma). It can be divided into three stratigraphically continuous substages (Santernian, Emilian, and Sicilian). The Calabrian Stage, which is commonly used to designate the lowest part of the Pleistocene, should be abandoned because its stratotype does not include a record of the first 500,000 yr of Pleistocene time.

Pliocene sapropels in the northern Adriatic area: chronology and paleoenvironmental significance

Abstract A detailed stratigraphic and paleoenvironmental study was carried out ona marine section from the Marecchia Valley in the Northern Apennines. The section consists predominantly of deep-water hemipelagic clays intercalated with 15 thick, laminated sapropels (M1–M15). Based on biostratigraphic (calcareous nannoplankton and planktonic foraminifera) and magnetostratigraphic results, the Marecchia Valley section is interpreted as being middle to late Pliocene in age, extending from the upper part of the Gauss Chron to the lower part of the Matuyama Chron. The high resolution stratigraphy allows us to correlate, for the first time, these northern Italian sapropels with sapropels previously described from the southern Mediterranean region. Based on this long-distance correlation, we conclude that the sapropels from throughout the Mediterranean have a common origin that is related to astronomical forcing. Specifically, these Pliocene sapropels are related to wet climatic conditions in the Mediterranean and surrounding borderlands and are linked to precission minima which are times of increased precipitation. This is consistent with our pollen data, which indicate that very wet conditions existed during sapropel formation. Additionally, the planktonic and benthic foraminiferal assemblages associated with sapropels indicate that these were periods marked by high surface productivity and low bottom water oxygen.

The occurrence and significance of Pleistocene and Upper Pliocene sapropels in the Tyrrhenian Sea

Numerous sapropels and sapropelic strata from Upper Pliocene and Pleistocene hemipelagic sediments of the Tyrrhenian Sea show that intermittent anoxia, possibly related to strongly increased biological productivity, was not restricted to the eastern Mediterranean basins and may be a basin-wide result of Late Pliocene-Pleistocene climatic variability. Even though the sapropel assemblage of the Tyrrhenian Sea clearly originates from multiple processes such as deposition under anoxic conditions or during spikes in surface water productivity and lateral transport of organic-rich suspensates, many “pelagic sapropels” have been recognized. Stratigraphic ages calculated for the organic-rich strata recovered during ODP Leg 107 indicate that the frequency of sapropel formation increased from the lowermost Pleistocene to the base of the Jaramillo magnetic event, coinciding with a period when stable isotope records of planktonic foraminifera indicate the onset of climatic cooling in the Mediterranean. A second, very pronounced peak in sapropel formation occurred in the Middle to Late Pleistocene (0.73-0.26 Ma). Formainifers studied in three high-resolution sample sets suggest that changes in surface-water temperature may have been responsible for establishing anoxic conditions, while salinity differences were not noted in the faunal assemblage. However, comparison of sapropel occurrence at Site 653 with the oxygen isotopic record of planktonic foraminifers established by Thunell et al. (Proc. ODP, Sci. Results 107, 1990) indicates that sapropel occurrences coincide with negative δ18O excursions in planktonic foraminifers in thirteen of eighteen sapropels recognized in Hole 653A. A variant of the meltwater hypothesis accepted for sapropel formation in the Late Pleistocene eastern Mediterranean may thus be the cause of several “anoxic events” in the Tyrrhenian as well. Model calculations indicate that the amount of oxygen advection from Western Mediterranean Deep Water exerts the dominant control on the oxygen content in deep water of the Tyrrhenian Sea. Inhibition of deep-water formation in the northern Adriatic and the Balearic Basin by increased meltwater discharge and changing storm patterns during climatic amelioration may thus be responsible for sapropel formation in the Tyrrhenian Sea.

An overview of the post‐Messinian paleoenvironmental history of the western Mediterranean

A review of the Pliocene-Pleistocene paleoenvironmental history of the western Mediterranean is presented based on micropaleontological and geochemical studies of Ocean Drilling Program (ODP) leg 107 material and marine outcrops in southern Italy. The calcareous plankton biochronology proposed for the Mediterranean by Rio et al. (1990 and 1991a) provides the necessary age control for determining the timing of major climatic and oceanographic changes in the region. The early Pliocene period in the Mediterranean was not a time of warm, stable climate; rather, it was marked by relatively high-amplitude climatic oscillations. In marginal areas, these climatic oscillations resulted in the rhythmic deposition of limestone-marl couplets which have an average duration of approximately 19,000 years. It is proposed that these sedimentary couplets are the result of precessionally induced changes in monsoon intensity which in turn cause variability in coastal divergence and upwelling. The δ18O and the calcareous plankton (foraminifera and coccoliths) records for Tyrrhenian Sea ODP site 653 reveal a cooling of surface waters at ∼3.1 Ma. Coincident with this cooling is an increase in the frequency of diatomite formation in southern Italy (Bianco section). The global cooling at ∼2.4 Ma and the associated expansion of northern hemisphere glaciation resulted in a shift to more arid conditions in the Mediterranean region. This climate change may have altered the Mediterranean water balance, resulting in the establishment of antiestuarine water exchange with the Atlantic at this time. The δ18O record for site 653 is also marked by a sharp cooling across the Pliocene/Pleistocene boundary. In the boundary stratotype section at Vrica, this cooling is manifested as an increase in the abundance of the planktonic foraminifer Neogloboquadrina pachyderma.

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.

Messinian salinity crisis and its paleogeographical implications

Abstract During the Late Messinian (uppermost Miocene) the region that is now Italy was occupied by a lake or system of lakes similar to those of the Paratethys existing to the east. Lacustrine deposits are known, not only in Italy, but extending southward through Sicily into the northern part of Tunisia. These strata contain faunas tyoical of a hyposaline environment. The lakes generally exhibit shallow-water characteristics and follow the structural trends of the “geosynclinal” development of Italy during the Late Miocene. We conclude that the water level ofthe hyposaline lake system was conspicuously lower than the general level of the World Ocean system. We support the point of view that the western Mediterranean was in a state of partial desiccation. In the area studied, the sharp contact between Miocene and Pliocene deposits points to a sudden change from a region of shallow lakes or subaerial erosion to the deposition of deep-water sediments. The sudden appearance of d deep-water environment is explained if the Pliocene transgression is considered to be a consequence of the re-establishment of communications with the open sea.